Improvements in Baths for Toughening, Strengthening, and Hardening Iron and Steel.
Year: 1894

page_text: Date of Application, 19th Jan., 1894-Accepted, 5th May, 1894
COMPLETE SPECIFICATION.
Improvements in Baths for Toughening, Strengthening, and
Hardening Iron and Steel.
I, FRANCIS GORDON BATES of 2027 North College Avenue in the City of
Philadelphia, State of Pennsylvania, United States of America, Mechanical
Engineer do hereby declare the nature of my invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement :—
My invention relates to improved liquid baths for treating low grade steel or
malleable iron for the purpose of increasing fineness of grain of the inetal and
improving its qualities of tensile strength, toughness ductility and elasticity and
also, when desired, rendering it harder than before.
With this object in view my invention consists of a bath having as a foundation
a brine preferably formed with both alum and common salt (chloride of sodium) to
which brine is added, oil, benzine, or equivalent liquid which, when subjected to
heat, will cause the evolution of hydrocarbon gas, further additions being certain
salts such as salts of ammonia, potassium, aluminium and zinc, and sometimes lime,
some of these salts being replaced by others, such as arsenic and phosphate of lead
in some cases.
The salts of aluminium sodium and potassium and the lime are used for the
purpose of strengthening or toughening the metal, or increasing its ductility, the
hydrocarbon gas for the purpose of increasing the percentage of carbon therein;
the ammonium salts for the purpose of developing, under heat, ammonia gases, and
the phosphate of lead and arsenic for hardening purposes.
In carrying out my invention the ingredients employed and the proportions of
the said ingredients may be varied in accordance with the character of the metal
under treatment or with the result which it is desired to obtain. The following is
an example, of a bath which I have found to be effective in treating low grade
steel.
To each gallon of alum brine of a strength of from 50° to 70° Baumé I add
three ounces of glycerine oil and three ounces of benzine (or six ounces of either
the said oil or the said benzine to the exclusion of the other) eight ounces of sal
ammoniac, or chloride of ammonium, three ounces of sulphate of ammonium,
four ounces of sulphate of zinc, six ounces of potassium nitrate (or spirits of
nitre) sixteen ounces of fluoride of aluminium and sixteen ounces of hydrated lime.
The articles to be treated are heated to a bright red heat and are then introduced
into the bath and allowed to remain therein until they become cold, or until their
heat is so far reduced that no further gas will be developed in the bath.
A bath of this character is intended for treating billets or pieces of a thickness
not greater than three and a half or four inches. If thicker pieces are to be
treated I prefer to add two ounces of aqua ammonia, two ounces of sulphate of
alumina and about treble the quantity of sal ammoniac, and fluoride of aluminium.
For treating malleable iron castings I have used with good results a bath
consisting of one gallon of alum brine of a strength of 50° to 70° Baumé, one gallon
of salt brine of a strength of 40° to 50° Baumé, ten ounces of glycerine, oil, or of
benzine, or a proportionate quantity of each, eleven ounces of sal ammoniac or
chloride of ammonium, fourteen ounces of sulphate of zinc, seven ounces of
potassium nitrate, three ounces of spirits of nitrė, sixteen ounces of fhioride of
aluminium, thirty two ounces of hydrated lime, six ounces of chromate of potassa
and fourteen ounces of sulphate of alumina.

page_text: The articles to be treated are heated to a red heat and then dipped into the bath
and permitted to remain until the evolution of the gas ceases.
The zinc salt is used for preserving the bath, and its use as well as the use of the
lime may be dispensed with without materially detracting from the success of the
treatment.
When it is desired to harden the metal, I use in place of the sodium and
potassium salts, other salts such as phosphate of lead and arsenic, which will have a
hardening effect. For instance, a bath for this purpose may be made as
follows:-
To one gallon of alum brine is added six ounces of oil or benzine, one-half ounce
of phosphate of lead, four drachms of arsenic, three ounces of sal-ammoniac and
three ounces of sulphate of zinc, the treatment being the same as before.
Although I have described the use of glycerine oil and benzine, other oils such
as fish or animal oils or fats, crude petroleum or the like may be used, the purpose
of these ingredients being to generate hydrocarbon gases when heated, and
although I have described a variety of ammonium salts, the use of these may be
limited in accordance with the desired generation of ammonia gases in the bath.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The within described bath for treating iron or steel, said bath consisting of brine,
hydrocarbon oil or oils, and ammonia salts or salts, with the addition of salts such
as those of sodium or potassium for toughening the metal or increasing ductility of
phosphate of lead and arsenic for hardening and with or without the addition of
sulphate of zinc and lime, substantially as specified.
Dated the 19th day of January 1894.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, Agents.