US2027837A - Process for making alloys - Google Patents

Description

Patented Jan. 14, 1936 UNITED STATES PROCESS FOR MAKING ALLOYS William C. Read, New Rochelle, N. Y., assignor to Electro Metallurgical Company, a corporation oi. West Virginia No Drawing. Application July 21, 1934, Serial No. 736,343

Claims.

The invention is a process for making metals and metallic alloys containing relatively large amounts of nitrogen. A major object of the invention is to provide a method for introducing nitrogen into ferrochromium, but the process of the invention may be used to introduce nitrogen into any metal or alloy having a substantial afflnity for nitrogen.

Until recently, nitrogen was considered to be an undesirable impurity in ferrochromium, and every effort was made to keep the percentage of this element as low as possible. It is now known that a ierrochromium containing nitrogen in relatively large amounts, preferably about one 5 one-hundredth or more of the chromium content, is usei'ul in making certain alloy steels, and there is a considerable demand for such an alloy. Although several methods of making high-nitrogen Ierrochromium are known, they are for one reason or another comparatively expensive, and

it is an object of the present invention to provide a new and relatively inexpensive process for making this commodity.

The process of my invention comprises intimately mixing the ierrochromium, or other metal or alloy to be treated, with a nitrogen-containing oxidizing agent such as a nitrate and a strong reducing agent such as silicon or aluminum, and then reacting the oxidizing and re- 7 ducing agents, whereby the ferrochromium is melted by the heat of reaction and the nitrogen liberated by the reaction is brought into intimate contact with the mol en Ierrochromium.

Suitable nitrogen-containing oxidizing agents include ammonium nitrate and the nitrates of sodium, potassium, and calcium. Nitrites may be used; but they are less effective than nitrates.

The reducing agent may be present in the form of an alloyed constituent of the ierrochromium, or it may be added as a separate metal or alloy, or both sources may be used. Silicon in the form of a ierrochromium-silicon alloy is an especially convenient reducing agent.

The following example illustrates the practice of the invention. A charge consisting. of:

Pounds 'Ferrochromium (high silicon) 1500 Sodium nitrate 405 50 Lime 45 the constituents of which were separately ground to 100 mesh and finer and then thoroughly mixed, was placed in a refractory-lined iron container and ignited by a hot wire and a primer consist- 55 ing of a handful of magnesium powder placed on top of the charge. The ferrochromium used in the charge analyzed:

Per cent Chromium 66.04 Silicon 9.10 5 Carbon 0.05 Nitrogen 0.06

The exothermic reaction was completed in about one minute and the fluid products were The amount of silicon oxidized in the process is in most cases between about 4% and 15% of the total weight of the charge, and the oxidizing 20 agent is appropriately proportioned to consume the desired amount of silicon. If the proportion of reactants to inert materials in the charge is too small, the reaction is sluggish, the products are insufliciently fluid and the. losses of chromium 25 by oxidation are relatively large. If too large a proportion of reactants to inert materials is used, the reaction is unduly violent and the consumption of oxidizing agent is excessive. The best operating conditions will ordinarily call for the consumption of about 7% to 12% silicon based on the total weight of the charge.

It is possible to control the nitrogen content of the alloy by varying the depth of charge in the furnace, a shallow charge yielding a lower nitrogen product than a deeper charge.

It will readily be understood that the invention is not limited to or by the specific example given herein by way of illustration, but that numerous 40 variations and modifications are possible. For instance, the process is equally well suited for the production of high-carbon alloys and lowcarbon alloys.

I claim:

1. Process for making metals and metallic alloys containing relatively large amounts of nitrogen which comprises reacting an exothermic mixture of a nitrogen-containing oxidizing agent and a strong reducing agent in close association with the metallic constituents of said alloy, at least one of said constituents being a metal that has a substantial afiinity for nitrogen and said mixture being substantially free from metal oxides; whereby the said constituents are melted and nitrogen liberated by the reaction is brought into contact with the said molten constituents.

2. Process for making chromium alloys containing relatively large amounts of nitrogen which comprises reacting a nitrate and a reducing agent of the group consisting of silicon and aluminum in close association with the metallic constituents of said alloy and in the absence oi. substantial amounts of metal oxides; whereby the said constituents are melted and nitrogen liberated by the reaction is brought into contact with the said molten constituents.

3. Process for making high-nitrogen terrochrornium which comprises reacting a charge including metallic chromium, iron, and silicon, and. a nitrate, the silicon forming about 4% to 15% or the total weight of the charge and the nitrate being proportioned to react with substantially all of the silicon; said charge being substantially free from metal oxides.

4. Process for making high-nitrogen ferrochromium which comprises reacting a charge including metallic chromium, iron, and silicon, and a nitrate, the silicon forming about 7% to 12% of the total weight of the charge and the nitrate being proportioned to react with substantially all of the silicon; said charge being substantially free from metal oxides.

5. Process for making high-nitrogen terrochromium which comprises reacting'a finely subdivided and intimately mixed charge including metallic chromium, iron, and silicon, and sodium nitrate, the silicon forming about 7% to 12% of the total weight of the charge and the sodium nitrate being proportioned to react with substantially all of the silicon; said charge being substantially free from metal oxides.

WILLIAM c. READ. 20