US1942937A - Process of heat treating ferrous metals - Google Patents

Description

Patented Jan. 9, 1934 UNITED STATES PROCESS OF HEAT TREATING FERROUS METALS V James A. Robertson and David Robertson, To-

ronto, Ontario, Canada, assignors of one-half to George F. McCandless, Toronto, Canada No Drawing. Application June 20, 1932 Serial No. 618,297

Claims.

The principal objects of this invention are to enable the conversion of low carbon ferrous metals such as iron or soft steels into high carbon steel with an increased tensile strength and hard- 5 ness in a remarkably short period and at very moderate cost.

The principal feature of the invention consists in the novel admixture of materials in which the metal to be treated is packed to be heat treated whereby the grain of the metal is affected to increase porosity and a high percentage of silicon content of the metal is removed and a remarkable degree of'penetration of other metals and carbon are effected in the minimum of time.

According to this process a thorough mechanical mixture of materials in finely ground or powdered form is prepared in or about the following proportions Percent Charcoal 40 Hardwood Sawdust 24 Chromium 5 Manganese 20 Borax 8 25 Pea chop 3 The metal to be treated is packed in suitable iron boxes or flasks, each piece being completely surrounded with the ground mixture as is the usual practice for pack treatment.

The flasks are then placed in a suitable furnace and are brought to a temperature of from 1850 F. to 1950 F. and retained under such temperature for a period sufficient to obtain the desired penetration, it being found that treatment at the above temperature obtains approximately 1%" of penetration in two hours and the admixture of materials is such that any degree of penetration up to complete penetration may be obtained.

It will of course be understod that the dimensions and volume of the metal pieces being treated will require widely varying periods of time to attain the furnace temperature and that the treatment is carried on in periods of time to attain the furnace temperature and that the treatment is carried on in periods, following complete heat penetration, in accordance with the desired carbon penetration.

The use of borax with the manganese and chromium salts is found to produce an extremely desirable result in effecting deep penetration of the foreign metal substances into the iron or mild steel being treated and the penetration is assisted by the continued supply of carbon effected by the presence of the pea chop and hardwood saw dust following the initial application of carbon supplied by the charcoal.

The pea chop, which consists of pea vines, pods and peas finely chopped, with the hardwood sawdust, provides a solid base for the metal to 50 be treated and prevents warping.

Under the heat-treatment the pea chop has the effect of opening the grain of the metal thereby assisting the penetration of the borax which acting as a purifier removes corrosion in the metal 5 and eliminates a portion of the silicon.

The opening of the grain permits the ready penetration of the manganese and chromium and also the carbon produced by the charcoal and sawdust. The use of sawdust maintains the production of carbon beyond the period of the production of carbon from the charcoal in the mixture.

Ferrous metals heat treated in the manner described have a hard but not brittle surface and a very desirable quality of steel is produced.

It will of course be understod that the proportions of the materials used may be varied in accordance with the quality of the metal being treated.

What we claim as our invention is:-

1. A process of heat treating ferrous metals, consisting in first preparing a mixture of finely ground carbonizable materials, manganese, chromium and borax, then packing the metal articles to be treated in such mixture, then raising the temperature of the entire body of materials to from 1850 F. to 1950 F. and maintaining such temperature for a period to effect the desired penetration of the resultant substances into the grain of the metal.

2. A process of heat treating ferrous metals, consisting in preparing a mixture of finely ground materials in or about the following proportions:

Per cent Charcoal 40 Hardwood sawdust 24 Manganese 20 Chromium 5 Borax 8 Pea chop 3 then packing the metal articles in such mixture, then heating the mass to attain a temperature of from 1850 F. to 1950" F. and maintaining such temperatures for a period of approximately two hours for each of carbon penetration of the metal desired.

3. A process ofheat treating ferrous metals, consisting in first preparing a mixture of finely the desired penetration of the carbon, manganese and chromium into the grain of the metal.

4. A compound for use in the heat treating of ferrous metals containing manganese, chromium, borax and a carbonizable material.

5. A compound for use in the heat-treating of ferrous metals containing manganese approximately 20%, chromium approximately 5%, borax approximately 8%, in combination with approximately 67% carbonizable material.

JAMES A. ROBERTSON. DAVID ROBERTSON.