Corrosion resistant bronze alloys and glass making mold made therefrom

A bronze alloy composition for glass making molds that has excellent corrosion resistance and resistance to pitting, the composition comprising copper, aluminum, nickel, iron, manganese, and a critical amount of silicon to provide the resistance to pitting.

The present invention relates to a corrosion resistant bronze alloy that is 
resistant to pitting when contacted by hot glass. The invention also 
relates to glass making molds and mold members and a method of making the 
same using the bronze alloys. 
BACKGROUND OF THE INVENTION 
The McCausland U.S. Pat. No. 4,436,544 discloses an aluminum bronze alloy 
composition for glass making molds and mold members. The alloy 
compositions are made of aluminum, nickel, manganese and iron, with the 
balance being copper. Alloys 3 and 4 of Table 1 (col. 3) are shown to 
contain the following ingredients in percent by weight: 
______________________________________ 
Alloy 3 
Alloy 4 
______________________________________ 
Aluminum 8.0-14.0 8.0-14.0 
Nickel 2.0-10.0 2.0-10.0 
Iron 0.1-6 0.1-6.0 
Manganese 3.1-5 6.1-8.0 
Copper 67.0-85.0 
66.0-84.0 
______________________________________ 
Alloys 3 and 4 and other alloys disclosed in the McCausland patent have 
many desirable properties including very high thermal conductivities. 
The McCausland U.S. Pat. No. 4,436,544 is hereby incorporated by reference. 
It is desirable to have bronze alloys for glass making molds and mold 
members that have the good balance of properties of the alloys of the 
above mentioned McCausland patent, with even better corrosion resistance, 
especially with a reduction in pitting and a lower thermal conductivity. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide a new bronze alloy with 
superior properties of resistance to especially resistance to pitting, the 
bronze alloy glass making molds and mold members being made from a bronze 
alloy composition comprising the following metals in approximate weight 
percent: 
______________________________________ 
Metal Percent by Weight 
______________________________________ 
Aluminum 8-12 
Nickel 12-18 
Iron 1-6 
Manganese 1.5-6 
Silicon 0.1-2 
Copper the balance, preferably 
64-84 
______________________________________ 
It is an object of the present invention to provide a method of making a 
glass making mold member, the method comprising: forming the mold member 
from a bronze alloy composition consisting essentially of the following 
ingredients in approximate percent by weight: 
______________________________________ 
Ingredients Percent by Weight 
______________________________________ 
Aluminum 8-12 
Nickel 12-18 
Iron 1-6 
Manganese 0.5-6 
Silicon 0.1-2.0 
Copper balance 
______________________________________ 
These and other objects of the invention will be apparent from the 
specification that follows and the appended claims. 
SUMMARY OF THE INVENTION 
The present invention provides an aluminum bronze alloy for glassmaking 
molds, the alloy having the following ingredients in approximate percent 
by weight: 
______________________________________ 
BG 650 
______________________________________ 
Aluminum (%) 8.0-12.0 
Nickel (%) 12.0-18.0 
Iron (%) 1.0-6.0 
Manganese (%) 0.5-6.0 
Silicon (%) 0.1-2.0 
Copper balance 
______________________________________ 
and the alloy having the following properties: 
______________________________________ 
Tensile Strength (psi) 
75,000-100,000 
Yield Strength (psi) 
35,000-60,000 
Elongation (%) 1.0-6.0 
Hardness (BHN) 175-250 
Thermal Conductivity 
36-40 
______________________________________ 
at 850.degree. F. (BTU/hr/ft.sup.2 /ft/.degree.F.), the alloy being 
corrosion resistant and resistant to pitting from contact with hot glass. 
The present invention also provides a bronze alloy glassmaking mold, the 
alloy having the following ingredients in approximate percent by weight: 
______________________________________ 
Ingredients BG 650 
______________________________________ 
Aluminum (%) 8.0-12.0 
Nickel (%) 12.0-18.0 
Iron (%) 1.0-6.0 
Manganese (%) 0.5-6.0 
Silicon (%) 0.1-2.0 
Copper (%) balance 
Tensile Strength (psi) 
75,000-100,000 
Yield Strength (psi) 
35,000-60,000 
Elongation (%) 1.0-6.0 
Hardness (BHN) 175-250 
Thermal Conductivity 
36-40 
______________________________________ 
at 850.degree. (BTU/hr/ft.sup.2 /ft/.degree.F.), the alloy being corrosion 
resistant and resistant to pitting from contact with hot glass. 
The present invention also provides a process of making glass making mold 
members from the aforementioned bronze alloy composition containing a 
critical amount of about 0.1 to 2 weight percent, based on the total alloy 
composition, of silicon. 
In the preferred embodiment of the invention, the amount of silicon is 
about 0.3 to 1 weight percent of the total alloy, the alloy composition 
containing the following elements in approximate weight percent: 
______________________________________ 
Element Percent by Weight 
______________________________________ 
Aluminum 8-11 
Nickel 14-16 
Iron 3-4 
Manganese 0.6-5 
Silicon 0.3-1.0 
Copper balance 
______________________________________ 
The bronze alloy of the present invention has many glass making equipment 
uses and it has many advantages as follows: 
(1) It has improved corrosion resistance. This means glass mold equipment 
made from it will last longer in corrosive environments, such as those 
caused by sulphur. With this alloy, the environment can be made more 
corrosive to help improve bottle making productivity. 
(2) It can easily be weld repaired because it does not contain zinc or 
lead. 
(3) It has improved bearing properties, thus reducing galling of mold 
parts. 
(4) It has a metallurgical structure that is not easily altered when 
exposed to heat; thus mold equipment made from this alloy has good 
dimensional stability. 
(5) It has a fine grain structure that can be achieved without the use of 
metal chillers. 
(6) It has a relatively high hardness and low ductility which enables mold 
equipment to resist wear and impact damage. 
(7) Although the alloy is relatively hard, it has acceptable machinability. 
(8) It has a thermal conductivity similar to that of the bronze alloys 
presently being used in the industry. This means glass mold equipment made 
from it will be compatible with current practices. 
(9) It can be used in the heat treated or as-cast conditions. 
(10) It can be produced in the foundry by blending together pure elements 
or those that have been combined for alloying purposes. This is the most 
economical way to produce most all alloys. Those glass mold alloys which 
contain zinc cannot be easily made this way due to safety reasons. 
The following examples illustrate the present invention, the bronze alloys 
made according to McCausland U.S. Pat. No. 4,436,544 except that a 
critical amount (0.1-2 weight percent) of silicon is used to provide 
superior corrosion resistance.

EXAMPLE 1 
Bronze alloys were made and cast to form glass making molds, the alloy 
composition being shown in Table I, alloy B (containing 0.5 wt% silicon) 
being an alloy of the present invention. Tests were made and the resultant 
corrosion resistance is shown in Table II and Table III. In Table III the 
alloy samples were heat treated at 1650.degree. for two hours and then 
cooled to room temperature before heating and testing. 
Table I, II and III are as follows: 
______________________________________ 
Chemical Compositions and Hardnesses of Bronze Alloys 
______________________________________ 
Alloy Al (%) Ni (%) Fe (%) Mn (%) Si (%) 
______________________________________ 
A 8.4 14.1 4.1 0.6 -- 
B 8.5 13.8 4.4 0.6 0.5 
______________________________________ 
As Cast Heat Treated 
Alloy Cu (%) Hardness (R.sub.B) 
Hardness (R.sub.B) 
______________________________________ 
A Base 93 90 
B Base 95 89 
______________________________________ 
*Samples were heated to 1650.degree. for two hours and slow cooled. 
TABLE II 
______________________________________ 
Relative corrosion resistance of as-cast bronze samples 
after being heated for 24 hours at the temperatures indicated 
Alloy 1100.degree. F. 
1200.degree. F. 
1300.degree. F. 
Average 
______________________________________ 
A 3.0 2.5 4.0 3.2 
B 1.5 2.0 2.0 1.8 
______________________________________ 
Explanation of code: 
1.0 No pits Excellent surface 
2.0 A few small pits Acceptable surface 
3.0 More pits Probably not acceptable surface 
4.0 Many pits Unacceptable surface 
TABLE III 
______________________________________ 
Relative corrosion resistance of as-cast bronze samples that 
were heated to 1650.degree. F. for two hours, slow cooled to room 
temperature and then reheated for 24 hours at the temperatures 
indicated. 
Alloy 1100.degree. F. 
1200.degree. F. 
1300.degree. F. 
Average 
______________________________________ 
A 3.0 4.0 4.0 3.7 
B 1.0 2.0 3.0 2.0 
______________________________________ 
Explanation of code: 
1.0 No pits Excellent surface 
2.0 A few small pits Acceptable surface 
3.0 More pits Probably not acceptable surface 
4.0 Many pits Unacceptable surface 
EXAMPLE II 
Excellent results, including superior resistance to pitting comparable to 
alloy B was obtained by the following alloy composition in approximate 
percent by weight: 
______________________________________ 
Aluminum 8.5 
Nickel 15.0 
Iron 4.6 
Manganese 0.6 
Silicon 0.3 
Copper balance 
______________________________________ 
The new alloy compositions of the present invention are obtained only when 
the critical range of about 0.1 to 2 weight percent of silicon is used, 
the properties falling off at the lower end and the higher end of the 
range. 
The Kelly Machine & Foundry U.S. Pat. No. 4,732,602 discloses a copper base 
alloy containing copper, nickel and aluminum, the nickel being 12-16 wt% 
and the aluminum being 8.5-11.5 wt%. Niobium and iron (up to 1 wt%) can be 
used. The patent indicates that small amounts of impurities are typically 
found in copper, the impurities including Sn, Pb, Zn, Sb, Si, S, P, Fe, Mn 
and Nb. The amount of Si by way of impurities is very low, generally about 
less than 0.01 wt% or 0.04 wt% (Examples 14 and 15). Such low amounts of 
Si do not provide the new alloy of the present invention with the critical 
range of Si deliberately included in the alloy rather than being present 
possibly only as an impurity.