US2131710A - Method of treating steel - Google Patents

Description

Patented Sept. 27, 1938 2.131.110 V Marnon or resume s'rm Vincent T. Malcolm, Indian Orchard, Mam, as-

signor to The Chapman Valve Mfg. 00., Indian- Orchard, Mara, a corporation of Massachusetts No Drawing. Application October 20, 1937, Serial No. 170,025

2 Claims. (Cl. 148-46) This invention relates to improvements in the treatment of steel.

The principal objects of this invention are directed to the provision of a novel process for treating austenitic steels.

The invention relates particularly to austenitic steels in order to take advantage of certain desirable characteristics of such steels and adapt the same to wider fields of usefulness.

Austenitic steels have desirable characteristics in that they resist corrosion but the surface characteristics thereof are not such that wear is resisted and they cannot be hardened as may other steels. When parts of. austenitic steel are in contact with one another or when a part of austenitic' steel is in contact with another steel and there is any relative movement, the austenitic steel has a tendency to score, scratch and seize.

As an example, when a valve or.seats of a valve are made from austenitic steel the action of one part on another causes the austenitic steel to scratch, score, seize or gall with the result that the unit is soon unfit for service, notwithstanding the fact the steel has otherwise such desirable characteristics as its ability to resist corrosion, temperature, etc.

According to this invention, austenitic steel is treated in such a way that it is hardened or at least its surface is hardened to the extent that it is definitely wear-resisting and does not tend to.

scratch, score and seize, while its resistance to corrosion and temperature is not impaired.

Therefore, the principal objects of this invention are directed to the provision of a process .and steels of the austenitic class wherein the steel has a hardened wear-resisting surface and new corrosion and temperature resisting characteristics so that the steel is adapted for use under such unfavorable conditions as elevated temperature and with agents capable of bringing about oxidation and corrosion.

Steels of the type to which the invention relates contains chromium and nickel in the relative percentages of, 18 and 8, with from .02 to 25% carbon, or wherein the chromium and nickel may be 25 and 12 percent respectively or in the reverse order.

In the practice of the invention, the austenitic steel to be treated is placed in a closed container which in turn is placed within a furnace so that the work is heated. The furnace may take the form of that described in U. S. Patent #l,9'l5,064 issued to me on September 25, 1934. The temperature will be in the neighborhood of 900 to 1700 F.

While the work or steel is being heated, the products of ammonia gas are conducted into contact with the work after being preferably passed 6 through a scrubber, dryer, cracker and catalyzer, all of which apparatus may be similar to that disclosed in my copending application Ser. No. 143,419 filed May 19, 1937. r

The resultant ammonia gas products are led 10 to the work and the heat is maintained at the temperature stated for one-half hourror more, after which the flow of ammonia gas products is cut oil.

Then ammonia gas is passed through an 15 ionizer unit, similar to that shown in U. S. Patent i i-1,975,063 issued to me September 25, 1934, and ledinto the compartment containing 'the work or steel.

The temperature employed is then from 850 F. 20 upwardly to 1400 and preferably in the neighborhood of 1100 F. The time of treatment under the conditions just stated is relatively longer than the time of the first treatment described above and will vary according to the size, shape, etc., 25 of the steel, and the particular results desired. The time of treatment may vary from 4 hours to as much as hours or more.

By the treatment described, steel may be produced whichis inherently resistant to oxidation 30 and corrosion and which has a surface-hardness, not touched by Nicholson test file; all to the end that it is wear-resisting and non-seizing and is adapted for many and various uses far beyond its original usefulness.

The ability of the steel to resist corrosion and oxidation of steam, boiler-feed waters, mineral and organic acids and basic salts at ordinary and elevated temperatures and its resistance to wear, scoring, scratching, and seizing are marked ren- 40 dering the steel adaptable for many and various uses heretofore unknown.

What it is desired to claim and secure by Letters Patent of the United States is:

l. The process of. treating chromium austenitic 45 steel which consists in. enclosing the steel to be treated in a closed container and heating the same, firstly flowing ammonia from a supply thereof into and through catalyzing and cracking units and into said container, and secondly in 50 cutting oil the flow of ammonia into said units and flowing ammonia directly from said supply to and through an ionizing unit and into said compartment.

2. The process of treating chromium austenitlc treated in a closed container, flratly flowing ammonia gas from a supply thereof into and through catalyzing and cracking units into said compartment and heating said steel within a range from 900' F. to 1700' It, and secondly cutsteel which come in, enclosing the ml to be e 0! the flow or. ammonia into m unite and flowing ammonia. hominid supply into and through an ionizing unit and into said comm-- ment and heating said steel within a range from 850' I". to 1400' I".

VINCENT 'r. mom.