US946360A - Treatment of iron or steel. - Google Patents

Description

UNITED STATES PATENT OFFICE.

WILLIAM RICHARD HOIDGKINSON, OF BLACKHEA'IH, ENGLAND.

TREATMENT OF IRON OR- STEEL No Drawing.

To all whom it may concern:

Be it known. that I, VILLIAM RICHARD Honoxrxsox, a subject of the King of Great Britain, residing at 18 Glenluce road, Blackheath, in the county of Kent, England, have invented certain new and useful' Improvements in or Relating to the Treatment of Iron or Steel, of which the following is a specification.

This invention relates to the treatment of iron or steel and has particular reference to the carburizing or case-hardening of iron or mild steel, the chief object being to enable this result to be attained in a simple, rapid and effective manner and to avoid the liability of the iron or steel, or article composed thereof, becoming deformed or otherwise rendered defective by being raised to an excessively high temperature.

According to this invention the iron or steel is heated to an appropriate temperature in contact with or in an atmosphere of a mixture of acetylene and ammonia gases.

In carrying the invention into practice the iron or steel is placedin a muffle or similar chamber which is heated to the'desired temperature and the gaseous mixture of acetylene and ammonia is passed into the said chamber, or materials which will yield the gaseous mixture are introduced'directly therein. Thus, calcium carbid may be added to a strong ammonia solution in which case a mixture of the two gases, ammonia and acetylene, is produced, or a mixture of calcium carbid and ammonium chlorid may be introduced into the heated chamber, the reaction which takes place in the latter case being represented by the following equation:

The component gases of the gaseous mixture are preferably in about the proportion of two volumes of ammonia to one volume of acetylene. however be employed, the only objection to proportions different from those above stated being that the excess of one or other of the gases is to some extent wasted; a

Specification of Letters Patent;

Any, other proportions may.

Patented Jan. 11, 1910.

Application filed August 29, 1907. Serial No, 399,624.

ture with ammonia prevents or checks mere decomposition of the acetylene or depos1-' tion of carbon in the form of soot. It is probable that cyanogen is formed and afterward decomposed, as it has been found that the iron or steel after treatment contains some nitrogen.

The steel produced by this process is much harder than ordinary case hardened steel Without chilling and the metal is hard ened to a much greater depth in a given time. In appearance it is, under the microscope, of fibrous or net like structure as distinguished from the granular structure of ordinary case hardened steel. This fibrous structure 1s not always apparent in chilled steel but the characteristic appearance can be readily brought out by heating to a high temperature and allowing it to' cool slowly.

The rate at which the iron or steel is being carburized or case-hardened can be ascertained and controlled by examining trial pieces, or by regulating the temperature or time of exposure. Thus, iron at a temperature of about 360 C and exposed to the gases for three or four hours will become carburized to about an equal extentif exposed for about ten minutes when the iron is heatedto 1000 C. As a further example, it may be stated that a bar of mild steel of one half a square inch in sectional area and containing .047 .of carbon when exposed to the gaseous mixture for thirty minutes ata temperature of from 500 to 600 C, is carburized to the hardness of steel containing about 1% of carbon.

When the result of the examination of test pieces indicates that the reaction is complete the iron or steel is removed from the furnace and applied to the various purposes for which case-hardened or carburized iron or steel is preferable or essential, as for example in the construction of armor plates.

What ters Patent of the United States is I claim and desire to secure byLet 1. The process of carburiz'ing or caseto the conjoint action of acetylene and ammonia gases.

2. The process of carburizing orcase llO hardening iron or steel which consists in subjecting the same, in a heated condition, to a mixture of acetylene and ammonia gases such that upon ignition the resulting flame is luminous but not very smoky, substantially as described.

3. The process of carburizing or case' hardening iron or steel Which consists in subjecting the same, in a heated condition, to a mixture of acetylene and ammonia gases the proportion of said gases being substantially one part acetylene to two parts ammonia gas, substantially as described.

4. The process of carburizing or case hardening iron or steel which consists in subjecting the same at a temperature sufficiently high to normally decompose acetylene gas, to a practically non-explosive mixture of acetylene and ammonia gases.

In testimony whereof I allix my signature in presence of two Witnesses.

WILLIAM RICHARD HODGKINSON.

Witnesses ARTHUR H. Coorn, RALPH M. SAW.