Surface treated steel sheet for battery containers, a battery container, and a battery produced thereof

Surface treated steel sheets for battery containers according to the present invention are composed of two surfaces, one of which is to be used as an inner surface of a battery container and the other as an outer surface of a battery container. On the inner surface, between the topmost nickel-tin alloy layer and the base steel sheet are formed intermediate layer(s) of nickel-iron, or nickel and nickel-iron, or nickel-tin-iron and nickel-iron. The present invention also relates to battery containers and batteries made from these surface treated steel sheets.

FIELD OF THE INVENTION 
The present invention relates to a surface treated steel sheet for battery 
containers, a battery container and a battery using the battery container. 
It especially relates to a surface treated steel sheet for battery 
containers for an alkali manganese battery, a battery container using the 
surface treated steel sheet and a battery using the battery container. 
THE BACKGROUND ART 
So far, the post-plating method wherein a drawn container produced from 
cold rolled steel strip is plated in a barrel plating or pre-plating 
method, where a nickel plated steel strip is drawn into a battery 
container, have been employed for battery containers used for primary 
batteries such as alkali manganese batteries, secondary batteries such as 
nickel cadmium batteries, and a nickel-hydrogen battery in which a strong 
basic solution is packed, that is expected to be increasingly in demand as 
a new secondary battery. The reasons why nickel plating is employed for 
battery containers such as those used for alkali manganese battery or 
nickel cadmium battery are as follows: 
1) a strong basic solution of potassium hydroxide is used as an electrolyte 
in these batteries, and nickel has excellent corrosion resistance to 
alkaline solutions. 
2) nickel has stable contact resistance when a battery is connected to an 
external terminal. 
3) spot welding is practiced when component parts are welded and assembled 
into batteries in the battery manufacturing process or when batteries are 
serially connected in order to increase voltage or when they are connected 
in parallel in order to allow large current flow, and nickel has excellent 
weldability. 
However, barrel plating causes unstable quality due to insufficient plating 
thickness and the difficulty of uniform deposition caused by insufficient 
circulation of plating solution deep into the bottom portion of the 
battery container when the inside of a tall cylindrical battery container 
is plated by barrel plating. On the other hand, although the 
above-mentioned problems are not caused in the pre-plating method, the 
battery container produced from a nickel-plated steel sheet, treated by 
thermal diffusion has improved corrosion resistance because the nickel 
plating layer is recrystallized and softened and thus has good 
extensibility. However, it has poor adhesion to the positive electrode mix 
because the inner surface of the positive electrode container (the battery 
container of the present invention) has small cracks and a smooth surface 
after drawing. 
Thereupon, battery performance has a close relationship to the properties 
of the inner surface of the positive electrode container (the battery 
container of the present invention) in an alkali manganese battery (see 
FIG. 2). The better the adhesion of the positive electrode mix (composed 
of manganese dioxide as the positive electrode active material, graphite 
as the conducting material and potassium hydroxide as the electrolyte) of 
the alkali manganese battery to the inner surface of the battery 
container, the better the battery performance. In the case of an alkali 
manganese battery, the positive electrode mix is in contact with the 
battery container and the battery container functions not only as a 
container but also as an electrical conductor that transmits electrons. 
Therefore, when the contact resistance between the positive electrode mix 
and the inner surface of the battery container is large, the internal 
resistance of the battery is likewise large, and battery performance is 
deteriorated by the resultant drop of current or reduction of discharge 
duration. Therefore, it is preferable to reduce the contact resistance 
between the positive electrode mix and the inner surface of the battery 
container as little as possible in order to obtain a high performance 
battery. 
Alkali manganese batteries are superior to manganese batteries in 
performance in high load electrical discharge where there is an especially 
large current flow, and the battery performance of the alkali manganese 
battery can be improved by reducing internal resistance of the battery. 
For the purpose of reducing the contact resistance between the positive 
electrode mix and the battery container to enable a large current flow, 
several methods such as roughening the inner surface of the battery 
container, providing grooves on the inner surface of the battery container 
in a lengthwise direction, and coating a conductive material composed of 
graphite added by binder on the inner surface of the battery container 
etc., are proposed. (See Battery Handbook, page 84, issued by MARUZEN in 
1990) 
Improvement in the contact between the positive electrode mix and the 
battery container causes a reduction of internal resistance, and 
consequently larger battery capacity can be obtained by reducing the 
amount of graphite in the positive electrode mix and increasing the amount 
of manganese dioxide as the positive electrode active material. Thus, 
battery performance depends considerably on the improvement of the 
internal resistance and particularly, the contact between the battery 
container and the positive electrode mix. 
However, the use of a roughened punch in order to roughen the inner surface 
of the battery container causes the problem where the rougher the punch, 
the lower the drawability, and the punch can not be roughened beyond a 
certain extent. 
Also, the use of a steel substrate having larger crystal grains to roughen 
the inner surface of the battery container after drawing causes the 
problem that the larger crystal grains result in a roughened surface at 
the positive electrode terminal and a deteriorated appearance for the 
battery container product in the case of a recently dominant pip type 
battery (the part of the positive electrode terminal of the battery 
container is convexly shaped). 
Further, although a conductive paint coating or conductive material coating 
on the inner surface of the battery container can reduce internal 
resistance, it also causes disadvantages such as an increase in the 
process of the battery manufacturing and an increase in production cost. 
Therefore, a battery material having a low cost of manufacture and low 
internal resistance is required for high performance alkali manganese 
batteries. 
SUMMARY OF THE INVENTION 
The surface treated steel sheet for a battery container of the present 
invention has one of the following structures: 
1) a nickel-tin alloy layer is formed as the uppermost layer on the surface 
that is to become the inner surface of a battery container; 
2) a nickel-tin alloy layer as the uppermost layer and a nickel layer as 
the lower layer are formed on the surface that is to become the inner 
surface of a battery container; 
3) a nickel-tin alloy layer as the uppermost layer, a nickel layer as the 
intermediate layer and a nickel-iron alloy layer as the lowermost layer 
are formed on the surface that is to become the inner surface of a battery 
container; 
4) a nickel-tin alloy layer as the uppermost layer and a nickel-iron alloy 
layer as the lower layer are formed on the surface that is to become the 
inner surface of a battery container; 
5) a nickel-tin alloy layer as the uppermost layer, an iron-nickel-tin 
alloy layer as the intermediate layer and a nickel-iron alloy layer as the 
lowermost layer are formed on the surface that is to become the inner 
surface of a battery container; 
6) a nickel-tin alloy layer as the uppermost layer, a nickel layer as the 
intermediate layer and a nickel-iron alloy layer as the lowermost layer 
are formed on the surface that is to become the outer surface of a battery 
container; 
7) a nickel-tin alloy layer as the uppermost layer and a nickel layer as 
the lower layer are formed on the surface that is to become the outer 
surface of a battery container; and 
8) a nickel layer is formed as the uppermost layer on the surface that is 
to become the outer surface of a battery container; 
The battery containers of the present invention are produced by drawing any 
surface treated steel sheet mentioned above in 1) to 8). 
The batteries of the present invention are produced using the 
above-mentioned battery containers, and the positive electrode mix 
(manganese dioxide+graphite as conductive material+potassium hydroxide 
solution as electrolyte) is packed on the positive electrode side and the 
negative electrode gel (granular zinc+potassium hydroxide solution as 
electrolyte) is packed on the negative electrode side in the battery 
container. 
Batteries having the structures mentioned above can have excellent battery 
performance such as a low internal resistance in the battery, a large 
short-circuit current and long discharge duration.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is described below in detail. 
First of all, the surface treated steel sheet of the present invention is 
explained. 
The surface treated layer of the steel sheet of the present invention has a 
different surface structure of the treated layer on either the side that 
is to become the inner surface of the battery container or the side that 
is to become the outer surface of a battery container as mentioned 
previously. 
With respect to the structure of the surface treated layer on the side that 
is to become the inner surface of a battery container a nickel-tin alloy 
layer or iron-nickel-tin alloy layer is first formed. The reason why these 
alloy layers are formed on the surface on the inner surface of a battery 
container is to cause numerous micro cracks in these layers when the 
surface treated steel sheet is drawn into a battery container. And another 
reason why these alloy layers are formed on the inner surface of a battery 
container is because when the steel substrate comprising a battery 
container is exposed on the surface of the battery container, the positive 
electrode mix will react with the iron present and form iron oxide, which 
serves to increase the internal resistance of the battery and cause a 
deterioration of the battery performance in the case of alkali manganese 
batteries. 
The thickness of the above-mentioned nickel-tin alloy layer or 
iron-nickel-tin layer is preferably in the range of 0.15 to 3.0 .mu.m, 
more preferably 0.2 to 2.0 .mu.m. When the thickness of the alloy layer is 
less than 0.15 .mu.m, smaller cracks are formed in the alloy layer in the 
drawing process, and the adhesion of the surface treated layer to the 
positive electrode mix is not improved, and consequently the internal 
resistance of the battery is not reduced. On the other hand, when the 
thickness of the alloy layer is more than 3.0 .mu.m, the effect of the 
improving adhesion of the surface treated layer to the positive electrode 
mix becomes saturated and the cost effectiveness is lost. 
The nickel-tin alloy layer can be formed either by nickel-tin alloy plating 
or by a process comprising a prior nickel plating and prior tin plating 
followed by heat treatment, which causes diffusion of tin into nickel, and 
the resulting formation of nickel-tin alloy layer. 
In addition, it is preferable that the nickel layer and/or iron-nickel 
alloy layer is formed under the nickel-tin alloy layer for the purpose of 
improving the adhesion of the nickel-tin alloy layer to the steel 
substrate as well as for improving the corrosion resistance of the entire 
surface treated steel sheet. Although the thickness of these layers is not 
particularly defined, a thickness less than 3 .mu.m is preferable based on 
economic considerations. 
Secondly, the structure of the surface treated layer on the side that is to 
become the outer surface of a battery container is explained. The reason 
why nickel layer is formed on the outer surface of a battery container is 
as follows: 
As the outer surface of a battery container is to be connected with an 
external terminal, a small and stable contact resistance and excellent 
corrosion resistance of the outer surface of the battery container are 
required for essential battery performance. 
The manufacturing process for the surface treated steel sheet is described 
below and as outlined in FIG. 1. 
Steel Sheet 
Aluminum killed steel is generally preferred as the substrate for plating. 
Non-aging hyper low carbon steel with added niobium, boron or titanium is 
also suitable. Usually, a steel strip that is electrolytically cleaned, 
annealed and skin-passed after being cold rolled is used as the substrate 
for plating. 
Nickel Plating 
After a pre-treatment consisting of electrolytic cleaning in alkali 
solution, rinsing in water, pickling in sulfuric acid or hydrochloric acid 
(electrolytic or dipping) and rinsing in water, the above-mentioned steel 
substrate for plating is plated with nickel. Any known nickel plating bath 
such as Watt bath, sulfamic acid bath or chloride bath can be used. Also, 
any type of nickel plating such as mat plating, semi-gloss plating or 
gloss plating can be used. Improvement in battery performance can be 
particularly expected when gloss plating is used as the nickel plating. 
The gloss plating process uses the plating bath comprising a nickel 
plating solution with an added organic compound containing sulfur 
(benzene-sulfonic acid derivatives such as sodium benzene-sulfonate or 
paratoluonesulfonamide, or saccharin), which gives luster to the plating 
with finely plated crystal grains by leveling the plating layer. Gloss 
plating also causes an extremely hard plating layer. 
The gloss plating process mentioned hereupon can be any one of the 
following processes: 
1) the one wherein a glossy nickel plating layer is directly formed on the 
steel substrate by gloss plating; 
2) the one wherein a mat finished nickel plating layer is formed on the 
steel substrate by mat plating followed by plating a glossy nickel plating 
layer on top; 
3) the one wherein a semi-glossy finished nickel plating layer is formed on 
the steel substrate by semi-gloss plating followed by plating a glossy 
nickel plating layer on top. 
Tin plating on the glossy nickel plating layer plated on the steel 
substrate followed by heat treatment is preferable because scaly cracks 
are also formed in the glossy nickel plating layer when the plated steel 
substrate is drawn. Numerous cracks are then formed in the entire plating 
layer and accompanied by micro cracks formed in the tin nickel plating 
layer, where, the crack density increases. 
In the present invention, a steel sheet is plated with nickel either on 
both sides or only on one side by a nickel plating selected from methods 
1) to 3) mentioned above. 
The thickness of the nickel plating layer plated on a surface that is to 
become the outer side of the battery container is in the range of 0.5 to 5 
.mu.m, preferably 1 to 4 .mu.m. In the case where nickel is plated on only 
one side of a steel sheet, it is plated on the surface that is to become 
the outer side of the battery container. 
The thickness of the nickel plating layer plated on a surface that is to 
become the inner side of the battery container is preferably in the range 
of 0.5 to 4 .mu.m, more preferably 1 to 3 .mu.m from the view point of 
harmony between battery performance and cost efficiency. When the 
above-mentioned thickness of the nickel plating is less than 0.5 .mu.m on 
the inner surface of the battery container, numerous pinholes are formed 
in the nickel plating layer, which undesirably cause the increased 
dissolution of iron (steel sheet) into the alkali solution that is the 
electrolyte solution within the battery, and increase the formation of 
iron oxide. 
The thickness of nickel plating less than 0.5 .mu.m on the outer surface of 
the battery container is also undesirable because corrosion resistance is 
apt to be deteriorated. 
Tin Plating 
The above-mentioned nickel plated steel sheet is followed by tin plating 
that is formed on both sides or the side that is to become the inner side 
of the battery container. 
While either the usual acid bath or the usual alkaline bath can be used, a 
stannous sulfate bath or a phenolsulfonic acid bath is preferably used in 
the present invention. When the tin plating layer is to be formed, the 
amount of tin plating is defined from the following view point. In the 
present invention, the entire tin plating layer should be converted into a 
nickel-tin alloy layer by a heat treatment which is used to form the 
nickel-tin alloy layer. This is because when the tin plating layer remains 
in the nickel-tin alloy layer after heat treatment, tin dissolves into the 
potassium hydroxide solution that is the electrolyte of the alkali battery 
and hydrogen is generated, which deteriorates battery performance. 
Therefore, it is essential that the entire tin plating layer is converted 
into nickel-tin alloy by heat treatment. When the plated steel sheet is 
heated below 700.degree. C. in the heat treatment process, the resultant 
nickel-tin alloy is mainly composed of Ni.sub.3 Sn, Ni.sub.3 Sn.sub.2 and 
Ni.sub.3 Sn.sub.4. As Ni.sub.3 Sn has the least amount of tin relative to 
nickel among these alloy compositions, tin is completely alloyed with 
nickel by heat treatment when tin, which is present in an amount less than 
that found in Ni.sub.3 Sn (atomic weight ratio of Ni:Sn is 3:1), is plated 
on a nickel plating, in which the amount of Ni is present in a greater 
amount than that found in the Ni.sub.3 Sn layer. Accordingly, the amount 
of tin should be less than 3 times the amount of nickel by the atomic 
weight ratio of tin to nickel. 
As the atomic weight of tin is 118.6 and that of nickel is 58.7, the atomic 
weight ratio of Ni:Sn is 3:1, so the ratio of amount of tin/amount of 
nickel is about 0.67 as shown in the following equation. 
EQU The ratio of amount of tin/amount of nickel=118.6/(58.7.times.3)=0.67 
When tin plating layer is formed at a larger ratio than that 
mentioned-above (about 0.67), the nickel required for the formation of the 
nickel-tin alloy layer is insufficient at the time of alloying treatment 
(heat treatment), and the tin plating layer remains as metallic tin as 
plated, which is not preferable for the present invention. 
In other words, when nickel is present in an amount that is about 1.48 
(=1/0.67; inverse of above-mentioned value 0.67) times the amount of tin 
that is plated, tin is totally alloyed into nickel-tin alloy during the 
heat treatment process, and tin does not remain as metallic tin, which is 
preferable for battery performance. 
Nickel-Tin Alloy Plating Another Method by which A Nickel-Tin Alloy Layer 
is Formed 
The above-mentioned method is one of the methods by which a nickel-tin 
alloy layer is formed, wherein after a tin plating layer is formed on a 
nickel-plated steel sheet, the plated steel sheet is heat treated to form 
a nickel-tin alloy layer. In the present invention, another method, 
wherein a nickel-tin alloy layer is directly formed on a steel sheet, is 
proposed. The use of this method followed by heat treatment improves the 
short circuit current in battery performance. 
The steel sheet used as the substrate for the above-mentioned nickel-tin 
plating can suitably be selected from the following two kinds of steel 
sheets. 
1) cold rolled steel sheet 
2) steel sheet previously plated with nickel 
As mentioned above, two types of methods for forming a nickel-tin alloy 
layer are proposed, and heat treatment is used after plating by either the 
first method or the second one because a nickel plating layer formed on 
the surface that is to become the outer side of the battery container can 
be recrystallized and softened by heat treatment (which is helpful for 
improving corrosion resistance of the battery container). 
The second mentioned method of nickel-tin alloy plating (another method for 
forming nickel-tin alloy layer) is described below in detail. 
Chloride-fluoride bath or pyrophosphoric acid bath is employed as a bath 
for nickel-tin alloy plating. The nickel-tin alloy layer can be formed on 
one side of a cold rolled steel sheet as well as on both sides of it. The 
thickness of the nickel-tin alloy plating layer formed on one side of 
steel sheet is different from that formed on the other side of the steel 
sheet. 
While a thickness range of 0.15 to 3.0 .mu.m is preferable on the surface 
that is to become the inner side of the battery container, a thickness in 
the range of 0.15 to 1.5 .mu.m is preferable on the surface that is to 
become the outer side of the battery container from the view point of 
corrosion resistance and contact electrical resistance. 
Heat Treatment 
In the first mentioned method for forming a nickel-tin alloy layer, nickel 
is plated on both sides of a steel sheet followed by plating with tin on 
at least one side of the nickel plated steel sheet and then heat treating 
to form nickel-tin alloy. Alternatively, nickel is plated on both sides of 
a steel sheet followed by heat treatment and then tin plating on at least 
one side of the nickel plated steel sheet followed by heat treatment to 
form a nickel-tin alloy. Furthermore, nickel can be plated on a steel 
sheet or on a nickel plated steel sheet followed by plating with 
nickel-tin alloy (the second method) and then heat treated. 
The heat treatment is preferably carried out under a non-oxidizing or 
reducing gas atmosphere in order to prevent the formation of an oxide film 
on the plated steel sheet. Heat treatment at about 200.degree. C. produces 
a nickel-tin alloy layer. When attempting to improve the corrosion 
resistance of the plating layer, particularly on the outer side of the 
battery container, by forming a nickel-iron diffusion layer between the 
nickel plating layer and the iron substrate (steel plate) accompanying the 
alloying treatment of nickel-tin alloy, heating at 450.degree. C. or more 
is required for the formation of a diffusion layer. More specifically, 
heat treatment is practiced in the temperature range of 450 to 850.degree. 
C. for a period ranging between 30 seconds to 15 hours. 
Either the box annealing process or the continuous annealing process can be 
used as the heat treatment process, and the preferred conditions for heat 
treatment is at a temperature between 600 to 350.degree. C. for 30 seconds 
to 5 minutes in the continuous annealing process, and at a temperature 
between 450 to 650.degree. C. for 5 to 15 hours in the box annealing 
process. In addition, an iron-nickel-tin alloy layer (3 component 
elements) can be formed between the steel substrate and the plating layers 
of nickel and tin in the present invention. For this case, after plating 
nickel on the steel substrate followed by tin plating on the nickel plated 
steel substrate, heat treatment at a rather high temperature for a longer 
period of time causes the mutual diffusion of the 3 component elements. 
Skin Pass 
Skin pass is carried out for the purpose of preventing origination of 
stretcher strains caused by heat treatment after nickel plating. Skin pass 
is carried out for the other purpose of obtaining a steel sheet having a 
desired surface roughness or appearance such as bright finish or dull 
finish by using working rollers having different surface roughness in the 
skin pass process. 
The present invention is described in more detail in the following 
examples. 
MANUFACTURING OF SURFACE TREATED STEEL SHEET 
EXAMPLE 1 
A cold rolled and annealed aluminum killed low carbon steel sheet having a 
thickness of 0.25 mm was used as a substrate for plating. 
The chemical composition of the presented steel sheet is as weight % as 
follows: 
C:0.04%, Mn:0.19%. Si:0.01%, P:0.012%, S:0.009%, Al:0.064%, N:0.0028% 
The steel sheet mentioned above was electrolytically degreased under the 
conditions described below. 
Electrolytical Decreasing in Alkali Solution 
Electrolysis Conditions; 
Bath composition: Sodium hydroxide 30 g/l 
Current density and treatment time: 
5 A/dm.sup.2 (anodic treatment).times.10 seconds and 
5 A/dm.sup.2 (cathodic treatment).times.10 seconds 
Bath temperature: 70.degree. C. 
After this treatment, the steel sheet was pickled in sulfuric acid (dipping 
in 50 g/l of sulfuric acid at 30.degree. C. for 20 seconds), and then 
plated with nickel under the conditions described below. 
Bath composition: Nickel sulfate 320 g/l 
Boric acid 30 g/l 
Sodium lauryl sulfate 0.5 g/l 
Bath temperature: 55.+-.2.degree. C. 
pH: 4.1.about.4.6 
Stirring: Air bubbling 
Current density: 10 A/dm.sup.2 
Anode: nickel pellet (nickel pellets were packed in a titanium basket and 
the basket was covered with a poly-propylene bag.) 
The steel sheet was mat nickel plated on one side or both sides, and the 
thickness of the plating layer was controlled by varying the duration of 
electrolysis under the above-mentioned conditions. 
After nickel plating, the plated steel sheet was tin plated on one side or 
both sides of the plated steel sheet in a stannous sulfate bath under the 
conditions described below. 
Tin Plating 
Bath composition: Stannous sulfate 30 g/l 
Phenolsulfonic acid 60 g/l 
Ethoxylated .alpha.-naphthol 5 g/l 
Bath temperature: 55.+-.2.degree. C. 
Current density: 10 A/dm.sup.2 
Anode: Plate of tin 
Several types of samples having various plating thickness were manufactured 
by varying the duration of electrolysis under the above-mentioned 
conditions. 
Next, after nickel and tin plating, the plated steel sheet was heat treated 
to form a nickel-tin alloy layer under the conditions described below. The 
atmosphere for heat treatment was as follows: 
Protective gas composed of 6.5% hydrogen and residual nitrogen and having a 
dew point of -55.degree. C. was used. 
Several types of surface treated steel sheets were manufactured by varying 
the soaking temperature and the soaking period. Those manufactured samples 
are shown as Sample 1 to 10 in Table 1. The thickness of the nickel 
plating layer, the nickel-iron alloy layer and the nickel-tin alloy layer 
shown in Table 1 were measured by GDS (Glow discharge emission spectral 
analysis). 
The surface analysis by x-ray diffraction analysis and GDS (Glow discharge 
emission spectral analysis) of sample in which a nickel plating layer was 
covered with tin and then heat treated showed the formation of nickel-tin 
alloy. The sample was manufactured as follows: a steel sheet was plated 
with nickel to a thickness of 2 .mu.m, and then plated with tin to a 
thickness of 0.75 .mu.m, and afterwards the plated steel sheet was heat 
treated at 500.degree. C. for 6 hours. 
It was found by X-ray diffraction analysis that the nickel-tin alloy layer 
produced from a two layered plating comprising nickel layer and tin layer 
and was mainly composed of Ni.sub.3 Sn. The hardening of the plating surf 
ace is supposed to be dependent on the precipitation of these inter 
metallic compounds. It was found that heat treatment at 300.degree. C. for 
6 hours mainly produced Ni.sub.3 Sn.sub.2 and that while heat treatment at 
higher temperatures produced an alloy layer richer in nickel content, heat 
treatment at lower temperatures produced an alloy layer richer in tin 
content. Furthermore, it was confirmed by GDS (Glow discharge emission 
spectral analysis) that heat treatment at 200.degree. C. for 1 hour also 
produced a nickel-tin alloy layer. 
EXAMPLE 2 
A surface treated steel sheet was manufactured using the same steel 
substrate as in Example 1 by the following manufacturing process wherein 
the steel sheet was plated with semi-glossy nickel, then plated with 
glossy nickel and finally plated with tin under the same tin plating 
conditions as in Example 1 followed by heat treatment and skin pass. 
The surface treated steel sheet was manufactured by a series of processes 
consisting of semi-glossy nickel plating on both sides of the steel sheet 
and subsequent glossy nickel plating on both sides of the steel sheet 
under the following conditions after electrolytical degreasing in alkali 
solution and pickling in sulfuric acid under the same conditions as 
described in Example 1. 
1) Semi-glossy nickel plating 
Bath composition: Nickel sulfate 300 g/l 
Boric acid 30 g/l 
Nickel chloride 45 g/l 
Sodium lauryl sulfate 0.5 g/l 
Brightener on the market 1.5 ml/l 
(unsaturated alcohol and unsaturated carboxyric acid based) 
Bath temperature: 55.+-.2.degree. C. 
pH: 4.0 to 4.5 
Stirring: Air bubbling 
Current density: 15 A/dm.sup.2 
2) Glossy nickel plating 
Glossy nickel plating was practiced under the following conditions after 
semi-glossy nickel plating shown in 1). 
Bath composition: Nickel sulfate 300 g/l 
Boric acid 30 g/l 
Nickel chloride 45 g/l 
Sodium lauryl sulfate 0.5 g/l 
Brightener on the market 1.0 ml/l 
(Benzene sulfonic acid derivative) 
Bath temperature: 60.+-.2.degree. C. 
pH: 4.3 to 4.6 
Stirring: Air bubbling 
Current density: 10 A/dm.sup.2 
Under the above-mentioned conditions, one side of the steel sheet was only 
plated with semi-glossy nickel and the other side of the steel sheet was 
plated with semi-glossy nickel and further plated with glossy nickel on 
top. 
Several types of samples having various nickel plating thicknesses by 
varying the electrolysis treatment time. The thus manufactured samples are 
shown as samples 11 to 14 in Table 2. 
EXAMPLE 3 
The steel substrate of Example 1 was mat nickel plated under the same 
conditions as Example 1 and subsequently plated with nickel-tin alloy 
using a chloride-fluoride bath. The conditions for nickel-tin alloy 
plating are as follows: 
Bath composition: Stannous chloride 50 g/l 
Nickel chloride 300 g/l 
Sodium fluoride 30 g/l 
Acid ammonium fluoride 35 g/l 
Bath temperature: 65.degree. C. 
pH: 4.5 
Current density: 4 A/dm.sup.2 
Anode composed of nickel-tin alloy containing 28% tin was used. Several 
types of samples having various thicknesses of nickel-tin alloy plating 
was obtained by varying the electrolysis treatment time. The thus 
manufactured samples are shown as samples 15 to 18 in Table 3. 
Explanation of the Battery Container 
Next, a method of manufacturing a battery container using the 
above-mentioned surface treated steel sheets is described below. 
The battery container of the present invention is produced from the surface 
treated steel sheets manufactured as mentioned above by deep drawing. The 
inventors of the present invention found that the application of the 
above-mentioned surface treated steel sheets as a battery container of 
alkali dry battery resulted in superior battery performance compared to 
using conventional battery containers. 
Inner Surface Structure of the Battery Container 
The internal resistance of an alkali manganese battery depends on the 
contacting state of the graphite as the conductive material in a positive 
electrode mix with the inner surface of the battery container. Namely, it 
is believed that the formation of uneven micro cracks on the inner surface 
of the battery container provides a wider area for contacting of the 
positive electrode mix with the inner surface of the battery container, 
which results in lower contact resistance and stronger adhesion, and 
consequently reduced internal resistance of the battery. 
Hereupon, it is believed that the internal resistance is reduced by the 
remarkable improvement of adhesion of the positive electrode mix to the 
inner surface of the battery container as the result of the formation of 
the cracks caused by drawing the surface treated steel sheet having an 
extremely hard nickel-tin alloy layer. In order to confirm this 
hypothesis, the inner surfaces of the conventional battery container and 
that of the present invention were observed under a microscope. The 
results are shown in FIGS 3A and 3B. FIG. 3A shows the inner surface of a 
conventional battery container produced by drawing a conventional nickel 
plated steel sheet, in which unevenness is observed only in the 
longitudinal direction of the container. FIG. 3B shows the inner surface 
of a battery container of the present invention which is produced by 
drawing the surface treated steel sheet obtained by successively plating 2 
.mu.m of nickel and 0.4 .mu.m of tin on a cold rolled steel sheet, and 
then forming a nickel-tin alloy layer by heat treatment of the plated 
steel sheet at 500.degree. C. for 6 hours, in which numerous micro cracks 
having diameters of several .mu.m are observed in the longitudinal 
direction of the container and in the circumferential direction as well. 
It is believed that the internal resistance of the battery is reduced by 
the penetration of the positive electrode mix containing graphite powder 
into the micro cracks formed on the inner surface of the container in the 
longitudinal and circumferential directions. It is supposed that the 
reason why numerous micro cracks are formed on the inner surface of the 
drawn container is because the nickel-tin alloy layer is hard and brittle. 
This feature of hardness and brittleness was confirmed by the following 
experiment. 
A cold rolled steel sheet was successively plated with 2 .mu.m of nickel 
and 1.6 .mu.m of tin, and then heat treated at 500.degree. C. for 6 hours. 
The hardness of the surface layer was measured to have a value of 860 with 
a micro Vickers hardness tester (load: 10 g). On the other hand, the 
surface hardness of a semi-glossy nickel layer having a thickness of 2 
.mu.m was measured to have a value of 355 and that of a nickel layer 
having a thickness of 2 .mu.m followed by the same subsequent heat 
treatment at 500.degree. C. for 6 hours as described above was measured to 
have a value of 195. 
The results showed that the surface layer consisting of tin layer plated on 
nickel plating layer followed by heat treatment was remarkably harder than 
those of 2 former surface layers (the one consisting of semi-glossy nickel 
plating alone and the one consisting of semi-glossy nickel plating 
followed by heat treatment). 
Outer Surface Structure of the Battery Container 
Although the type of surface treatment layer formed on the outer surface of 
the battery container is not particularly defined in the present 
invention, it is preferable to form a nickel plating layer since a small 
contact resistance, which is invariable over time, is required on the 
outer surface of the battery container. Furthermore, it is also preferable 
to form a nickel-tin alloy layer on a nickel plating layer in the present 
invention. As this alloy layer is extremely hard as mentioned above, 
scratch resistance is improved, and this can cover up a fault that the 
nickel plating layer is apt to be scratched by the drawing process or the 
battery manufacturing process as a result of softening of the nickel 
plating layer especially when it is heat treated to improve corrosion 
resistance after plating. A lower contact resistance is required on the 
outer surface of the battery container, and it can be attained by plating 
nickel-tin alloy on the surface that is to become the outer surface of the 
battery container. In the case where a steel sheet is plated with 2 .mu.m 
of nickel followed by plating with 0.75 .mu.m of tin on top and then by 
heat treatment at 500.degree. C. for 6 hours, the contact resistance 
measured 1.8 m .OMEGA. by 4 probe method. On the other hand, the contact 
resistance of the steel sheet plated with 2 .mu.m of nickel alone measured 
3.5 m .OMEGA.. Therefore,it can be seen that a nickel-tin layer is the 
surface treated layer having a lower contact resistance. 
The preferable thickness of the nickel plating layer formed on the outer 
surface of the battery container is in the range of 0.5 to 5 .mu.m, more 
preferably in the range of 1 to 4 .mu.m. It is preferable that this nickel 
plating layer is converted into a diffused nickel-tin alloy layer by heat 
treatment in order to improve corrosion resistance. When the nickel-tin 
alloy layer is formed on the inner surface of the battery container, the 
thickness of this alloy layer is preferably in the range of 0.15 to 3 
.mu.m, more preferably in the range of 0.2 to 2 .mu.m. Furthermore, when 
the nickel-tin alloy layer is formed on the outer surface of the battery 
container, the thickness of this alloy layer is preferably in the range of 
0.15 to 1.5 .mu.m. 
Explanation of Manufacturing of the Battery Container 
Battery containers for Tan-3 type (JIS LR-6) alkali manganese battery were 
manufactured from the above-mentioned surface treated steel sheet by 
drawing. 
At first, a circular blank was punched out from the above-mentioned surface 
treated steel sheet, and then it was drawn. After that the upper open edge 
portion of the battery container was trimmed off, and a cylindrical 
container having 49.3 mm in longitudinal length and 13.8 mm in outer 
diameter was manufactured under an 8 stage drawing process. 
Battery Manufacturing 
After manufacturing a battery container in the above-mentioned manner, a 
Tan-3 type (JIS LR-6) alkali manganese battery was manufactured as 
follows: 
At first, manganese dioxide and graphite were gathered together at a weight 
ratio of 10:1, then they were added with potassium hydroxide (8 moles) and 
mixed together to prepare the positive electrode mix. Afterwards the 
positive electrode mix was pressed in a metal mold, shaped in the positive 
electrode mix pellet having a doughnut shape and the prescribed 
dimensions, and then the thus produced pellets were compressively inserted 
into the battery container. Subsequently, the prescribed portion below the 
open edge of the battery container was necked-in processed in order to 
install a negative electrode plate made by spotwelding some negative 
electrode collecting rods into the battery container. Afterwards, a 
separator produced from a non-woven fabric made of VINYLON was inserted 
into the battery container along the inner circumference of the inserted 
pellets that had been compressively attached to the inner surface of the 
battery container, and then a negative electrode gel composed of granular 
zinc and potassium hydroxide saturated with zinc oxide was inserted into 
the battery container. Finally, after the negative electrode plate, 
installed with a gasket made of insulating material was inserted into the 
battery container, it was seamed with the battery container by caulking to 
form a complete alkali manganese battery. 
In the case where graphite was coated on the inner surface of the battery 
container, 80 parts by weight of graphite and 20 parts by weight of 
thermosetting epoxy resin were first dispersed in methyl ethylketone, then 
spray coated onto the inner surface of the battery container followed by 
drying at 150.degree. C. for 15 minutes. 
The battery performance of a Tan-3 type alkali manganese battery 
manufactured in the above-mentioned manner was measured after being kept 
at room temperature for 24 hours. Furthermore, in order to monitor any 
change in the course of time, the battery performance was also measured 
after the battery was stored for a month (30 days) in a thermo-hygrostatic 
room having a temperature of 60.degree. C. and a humidity of 90%. The 
battery performance was evaluated by measuring two characteristics of 
which one was the internal resistance (m .OMEGA.) by the alternating 
current impedance method (Frequency 1 kHz) and another was the 
short-circuit current (A) in which 1 m .OMEGA. was charged. Both 
measurements were carried out at 20.degree. C. The results are shown in 
Table 5. 
Comparative Example 
A steel sheet was nickel plated, successively heat treated under the same 
conditions as those of Example 1, and made into samples for the 
comparative example. The battery performance was evaluated in the same 
manner as that of Example 1. The results are shown as Samples 19 to 26 in 
Table 4. 
Samples 19 to 21 correspond to Example 1. Samples 19 to 20 of these samples 
had a higher initial internal resistance than those of the Example 1 in 
the evaluation of the battery performance, as well as exhibiting 2A to 3A 
lower short-circuit current than those of the Examples of the present 
invention. Sample 21 in which the inner surface was coated with graphite 
corresponds to Sample 9 and 10 of Example 1, and exhibited a higher 
internal resistance and a lower short-circuit current than those of the 
Examples of the present invention. 
Samples 22 to 24 correspond to Example 2. Samples 22 to 23 of these samples 
had a higher internal resistance and a lower short-circuit current than 
Samples 11 and 13. Sample 24 in which the inner surface was coated with 
graphite had a higher internal resistance and a lower short-circuit 
current than corresponding Samples 12 and 14. 
Samples 25 to 26 correspond to Example 3. Sample 25 of these samples had a 
higher internal resistance and a lower short-circuit current than those of 
Sample 15, and Sample 26 had a higher internal resistance and a lower 
short-circuit current then those of Sample 16. 
POSSIBILITY OF USE IN INDUSTRY 
As described above, the surface treated steel sheet of the present 
invention, in which a nickel-tin alloy layer is formed on the one side of 
a steel substrate that is to become the inner surface of a battery 
container, has a remarkably low internal contact resistance with the 
positive electrode mix and excellent alkali corrosion resistance when it 
is used as the material for a battery container. 
In addition, the battery container of the present invention manufactured by 
drawing, etc., in which the above-mentioned surface treated steel sheet is 
adopted for use, has the excellent properties of a low internal resistance 
and high short-circuit current on the inner surface of the battery 
container and a low contact resistance on the outer surface of the battery 
container. 
Furthermore, the battery of the present invention, in which the battery 
container of the present invention is used, has excellent battery 
performance such as a low internal resistance and high short-circuit 
current. 
TABLE 1 
__________________________________________________________________________ 
condition of the heat 
treatment after 
thickness plating thickness of the constructional layer 
of plating 
heated 
heated 
Fe--Ni Ni--Sn 
Fe--Ni--Sn 
Sample Ni Sn temp. 
time diffusion 
Ni layer 
alloy 
alloy 
No. Plating layer .mu.m .mu.m .degree. C. 
(min.) 
layer (.mu.m) 
(.mu.m) 
layer (.mu.m) 
layer (.mu.m) 
__________________________________________________________________________ 
EXAMPLE 
1 inner side 
Ni--Sn alloy formation 
1.8 
0.09 
500 360 1.86 0.43 
0.16 -- 
1 outer side Ni--Sn alloy formation 1.9 0.10 
1.75 
0.40 0.17 
-- 
inner side Ni--Sn alloy formation 2.0 0.15 500 360 
2.25 
0.28 0.32 
-- 
outer side 
Ni--Sn alloy 
formation 2.0 
0.74 
1.96 
0.15 0.60 
-- 
3 inner 
side Ni--Sn 
alloy formation 
0.5 0.36 500 
360 
0.53 -- 
0.61 
-- 
outer side 
Ni--Sn alioy 
formation 2.0 
-- 
1.96 
0.95 -- 
-- 
4 inner 
side Ni--Sn 
alloy formation 
1.1 0.73 500 
360 
0.93 -- 
1.09 
0.1 
outer side Ni 
plating 
1.8 -- 
1.9 
0.8 
-- 
-- 
5 inner side Ni--Sn alloy formation 1.9 0.74 300 
360 -- 
1.7 
0.73 
-- 
outer side Ni plating 2.0 -- 
-- 
1.8 
-- 
-- 
6 inner side Ni--Sn alloy formation 1.9 0.76 600 
360 4.41 
0.28 
0.81 
0.40 
outer side Ni--Sn alloy formation 4.8 0.75 
5.40 
0.15 0.60 
-- 
7 inner 
side Ni--Sn 
alloy formation 
1.9 1.52 500 
360 
1.25 -- 
0.70 
-- 
outer side Ni 
plating 
2.0 -- 
2.02 
0.9 
-- 
-- 
8 inner side Ni--Sn alloy formation 3.9 2.53 500 
360 2.35 
-- 
2.98 
-- 
outer side Ni--Sn alloy formation 4.0 1.49 
1.03 
2.83 1.80 
-- 
9 inner 
side Ni--Sn 
alloy formation 
1.0 0.38 500 
360 
1.34 -- 
0.65 
-- 
outer side Ni 
plating 
3.0 -- 
2.43 
1.63 -- 
-- 
10 inner 
side Ni--Sn 
alloy formation 
1.9 0.35 500 
360 
1.58 -- 
0.61 
-- 
outer side Ni 
plating 
2.2 -- 
2.13 
0.90 
-- 
-- 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
thickness 
of plating condition of the thickness of the 
sem heat treatment 
constructional layer 
bright 
bright after plating 
Fe--Ni Ni--Sn 
Fe--Ni--Sn 
Ni Ni 
Sn heated 
heated 
diffusion 
Ni alloy 
alloy 
Sample layer layer 
layer temp. 
time 
layer 
layer layer 
layer 
No. 
Plating layer 
(.mu.m) 
(.mu.m) 
(.mu.m) 
.degree. C. 
(min.) 
(.mu.m) 
(.mu.m) 
(.mu.m) 
__________________________________________________________________________ 
(.mu.m) 
EXAMPLE 
11 inner side 
Ni--Sn alloy formation 
0.9 
1.2 
0.09 
500 360 1.85 0.42 
0.15 
-- 
2 outer side Ni plating 2.2 -- 
-- 
1.72 
0.38 
-- 
12 inner 
side Ni--Sn 
alloy formation 
1.0 
1.1 
0.35 500 
360 
1.84 
0.43 0.60 
-- 
outer side Ni plating 2.2 -- 
-- 
1.73 
0.39 
-- 
13 inner 
side Ni--Sn 
alloy formation 
0.5 
1.5 
0.70 500 
360 
1.78 
0.40 1.08 
-- 
outer side Ni plating 2.3 -- 
-- 
1.72 
0.38 
-- 
14 inner 
side Ni--Sn 
alloy formation 
1.0 
1.9 
2.6 400 
300 
0.00 
2.90 2.94 
-- 
outer side Ni plating 2.3 -- 
0.72 
1.28 
__________________________________________________________________________ 
-- 
TABLE 3 
__________________________________________________________________________ 
condition of the 
thickness of the 
heat treatment constructional layer 
thickness 
thickness 
after plating 
Fe--Ni Ni--Sn 
of Ni 
of Ni--Sn 
heated 
heated 
diffusion 
Ni alloy 
Sample plating plating temp. time 
layer layer 
layer 
No. Plating layer (.mu.m) (.mu.m) .degree. C. (min.) (.mu.m) 
(.mu.m) (.mu.m) 
__________________________________________________________________________ 
EXAMPLE 
15 inner side 
Ni--Sn alloy plating 
1.0 0.17 550 300 -- -- 0.20 
3 outer side Ni plating 2.5 -- 2.3 
1.4 -- 
16 inner side Ni--Sn alloy plating 2.1 1.10 500 
480 
2.0 0.9 
1.10 
outer side Ni plating 2.0 -- 
2.3 
0.8 -- 
17 inner side 
Ni--Sn alloy plating 
1.9 2.03 
500 
480 2.03 
1.89 2.43 
outer side 
Ni plating 
3.2 -- 
2.5 1.8 -- 
18 inner side 
Ni--Sn alloy plating 
1.5 2.93 
500 
300 -- 
-- 3.30 
outer side 
Ni plating 
2.3 -- 
2.4 0.8 
__________________________________________________________________________ 
-- 
TABLE 4 
__________________________________________________________________________ 
conditionof the 
thickness of the 
thickness heat treatment constructional layer 
of after plating 
Fe--N Ni--Sn 
Fe--Ni--Sn 
plating 
heat 
heated 
heated 
diffusion 
Ni alloy 
alloy 
Samp Ni Sn treat- 
temp. 
time 
layer 
layer 
layer 
layer 
No. Plating layer (.mu.m) (.mu.m) ment .degree. C. 
(min.) 
(.mu.m) 
(.mu.m) 
(.mu.m) 
__________________________________________________________________________ 
(.mu.m) 
COMATIVE 
19 inner side 
Ni plating 
1.1 
-- none 
-- -- -- 1.1 -- -- 
EXAMPLE outer side Ni plating 1.9 -- -- 
1.9 -- 
-- 
20 inner 
side Ni plating 
1.9 -- 
none 
-- -- -- 
1.9 -- -- 
outer 
side Ni plating 
2.2 -- 
-- 
2.2 -- -- 
21 inner 
side Ni plating 
1.0 -- 
none 
-- -- -- 
1.0 -- 
-- 
outer side Ni plating 2.3 -- -- 2.3 -- -- 
22 inner side Ni plating 1.0 -- done 500 
360 1.7 
0.3 -- -- 
and heat 
treatment 
outer side Ni 
plating 1.9 
-- 
2.1 0.9 -- 
-- 
and heat treatment 
23 inner side Ni plating 2.0 -- done 600 
480 -- 
4.8 
-- -- 
and heat treatment 
outer side Ni plating 1.0 -- -- 4.7 -- -- 
and heat 
treatment 
24 inner 
side Ni plating 
1.2 -- 
done 
500 360 
1.6 
1.0 -- -- 
and heat treatment 
outer side Ni plating 1.9 -- 2.3 0.2 -- -- 
and heat 
treatinent 
25 inner 
side Ni--Sn 
alloy plating 
2.1 0.05 
done 500 
360 1.9 
-- 
0.09 -- 
outer 
side Ni plating 
2.2 13 
2.0 0.95 
-- -- 
26 inner side Ni--Sn alloy plating 2.0 Ni--Sn none -- -- 
-- 2.0 1.05 -- 
alloy 
plating 
1.05 
outer side Ni--Sn alloy plating 1.9 -- none -- -- -- 
1.9 -- 
__________________________________________________________________________ 
-- 
TABLE 5 
__________________________________________________________________________ 
graphite 
battery performance 
coating short curcuit current 
on the 
internal resitence (m.OMEGA.) 
first 
after 30 
sample 
inner 
first 
after 30 
stage 
days total 
No. surface stage days (ampere) (ampere) valuation 
__________________________________________________________________________ 
EXAMPLE 
1 1 none 101 125 8.3 6.7 good 
2 none 98 115 8.0 7.2 good 
3 none 99 113 8.4 7.5 good 
4 none 100 117 8.2 7.6 
good 
5 none 101 119 8.2 7.4 
good 
6 none 97 120 8.1 7.3 good 
7 none 95 118 8.4 7.5 good 
8 none 96 105 8.6 7.6 good 
9 existence 83 106 11.5 9.5 good 
10 existence 79 105 11.8 9.8 good 
2 11 none 85 110 10.7 9.0 good 
12 existence 72 101 
12.3 10.3 good 
13 none 83 109 
10.3 9.1 good 
14 existence 70 99 
12.5 10.1 good 
3 15 none 102 120 8.2 7.2 good 
16 none 98 115 8.7 7.1 good 
17 existence 79 98 11.8 9.5 
good 
18 none 85 105 8.6 7.5 good 
COMATIVE 19 none 125 143 5.6 4.0 
poor 
EXM 20 none 122 139 5.7 4.4 
poor 
21 existence 109 119 9.3 7.8 
poor 
22 none 128 139 5.5 4.2 
poor 
23 none 125 142 5.6 4.3 
poor 
24 existence 103 112 9.4 7.7 
poor 
25 none 128 140 5.3 4.5 
poor 
26 none 101 137 8.6 4.1 
__________________________________________________________________________ 
poor