US2117263A - Alloy - Google Patents

Description

Patented May 10, 1938 ALLOY Marvin J. Udy, Niagara Falls, N. Y., assignor, by mesne assignments, to Monsanto Chemical Company, a. corporation of Delaware NoDrawing. Application October 31, 1934, Serial No. 750,821

lClaim.

This invention relates to alloys of iron, chromium and phosphorus and to a process of producing the same.

One object of my invention is the provision of an alloy containing the elements iron, chromium and phosphorus in major proportion. It relates to an alloy or a series of alloys useful for introducing these elements into molten iron or steel as in the production of alloy steels. A still further object is the production of chrome-iron alloys low in carbon.

I am aware that it has been proposed to produce alloy steels containing, in addition to chromium, a relatively small proportion of phosphorus, the proportion recommended being from 0.15% to 0.5% phosphorus together with from 3% to 30% chromium. Such materials are special purpose steels recommended for certain uses and are not intended to serve for the subsequent production of alloy steels. 1

In the production of rustless or stainless iron or steel it is particularly necessary to obtain a low carbon content in the finished product in order that a workable material be had. This is accomplished in various ways, the most usual being the use of low-carbon ferro-chromium as the alloying constituent which supplies the chromium in the alloy.

Low-carbon ferrochromium is, however, difiicult to make and is expensive, hence a cheap method of producing the same was very much desired.

I have now found that if a chrome-iron alloy containing appreciable proportions of phosphorus is produced in the electric furnace, the alloy will contain much less carbon than in the absence of phosphorus. In other words, the phosphorus in my alloy effectively minimizes the absorption of carbon.

I have also found that the carbon absorbed by the alloy during manufacture depends upon the amount of phosphorus present. In other words, by increasing the phosphorus, I decrease the carbon content of the alloy. This discovery constitutes an eifective control over the carbon content, which discovery may be utilized in various ways.

Several examples will illustrate my process and the product obtained thereby.

Example I Mix together a furnace burden consisting of phosphate rock, silica, chrome ore and coke in the proportions of 53 pounds of phosphate rock, 47 pounds of chrome ore, 12 pounds of S102 pebble, and 21 pounds of coke. Charge to an electric arc furnace and melt down, using approximately 100 volts. After the ore has been completely fused, the furnace is tapped and slag and metal are withdrawn. The amount 01 metal obtained weighed 15.8 pounds, indicating a recovery of 82% of the theory. The metal analyzed as follows:

From the weights of materials charged to the furnace, I obtained a recovery in the alloy of 46.5% of phosphorus and 85.5% of chromium in the burden. The remainder of the phosphorus, except that entering the slag, was volatilized. The chromium not recovered in the alloy was volatilized.

Example II To a furnace burden such as was used in Example I above, I added 3.3 pounds of scrap iron.

This burden was then melted in the same manner, the furnace tapped, and the metal and slag separated.

The metal recovered amounted to 89% of the theory and analyzed as follows:

Percent Phosphorus i 18.4 Chromium 46.9 Iron 32.35

Carbon 2.19

Silicon 0.44

From the weights of material charged to the furnace, I obtained a recovery of 64.5% of phosphorus and 91.5% of chromium.

Example III From a burden consisting of. 60 pounds of chrome ore containing 31% of chromium and 11.26% iron, 60 pounds of Florida pebble phosphate rock, and 36 pounds of coke, I obtained,

upon smelting, 16 pounds of an alloy analyzing as follows:

Percent Phosphorus 15.05 Chromium 48.82 Silicon 4.24 Carb n a 1.41

The smelting operation was carried out in a furnace supplied with 100 volt alternating current. To aid in maintaining a fusible slag, I added a lime silicate slag to the furnace both at the/beginning and at the end of the run. A slag suitable for this purpose may be blast or electric furnace slag in which the SiO2CaO ratio is in the neighborhood of 0.7. If no such slag is available, I may add the constituents thereof, that is, lime and silica, directly to the burden in the required proportions.

From my observations on this operation it appears as if a refining of the metal with elimination of carbon takes place. This is believed to be due to the character of the slag employed. Additional refining may be carried out by exposing the molten metal in the furnace to the action of the lime-silica slag for a longer period of time. This refining operation serves to decrease the carbon content of the alloy, and apparently increases the silicon content at the same time.

The present alloy is particularly valuable from the standpoint of the production of low-carbon ferro-chrome. This material may be produced by refining the alloys described in the examples mentioned above, under a. basic oxidizing slag. By this means the phosphorus and carbon contents of the alloy are reduced. Such a slag is.

made up by using the ordinary lime-silica slag and adding iron ore or mill scale to the slag during the refining operation. In some cases the addition of chrome ore to the slag may be found desirable.

By suitably proportioning the constituents of the burden, I am able to produce alloys varying in composition. Alloys which Ihave produced in my process vary in phosphorus content between 3% and 20%; in chrome content between 15% v and and in iron content between 25% and These three constituents comprise the major ingredients in my alloy. The minor constituents will consist principally of carbon and silicon, the former varying from 0.5% to 5.0% and the latter varying between 0.05% and 6.5%, depending upon the character of the operation and the proportions of the major constituents present in the alloy.

My observations have led me to believe that the proportion of phosphorus present is of 0011- trolling significance with regard to the amount of carbon present in the alloy. I have found that the increasing amounts of phosphorus in my alloy makes for. a lower carbon content of the same. In this regard, silicon, although a minor constituent, is also of importance. The content of silicon is usually less than 6.5%, although it may be varied somewhat. Increasing the silica content of the burden and prolonging the smelting time increases the silicon content of the alloy. In a preferred form of my alloy the ratio of chromium to phosphorus will be greater than one and less than four, and the carbon content will'be between 1% and. 3.5%.' If a small proportion of silicon, say 4% to 6%, be present in this alloy, the carbon content will generally be If the chromium to phosphorus ratio be greater than four and less than, say, seven, the carbon content will be higher, that is, between 3.5% and 4.5%. As above stated, the carbon content in this case is also influenced by the silicon present, larger amounts of silicon decreasing the carbon to the lower values of this range.

Having nowdescribed my invention and the manner in which it may be used, it will be apparent that it is susceptible to various changes and modifications without departingfrom the spirit thereof, and I desire, therefore, that it be not limited except as necessitated by the prior art or as specifically set out in the appended claim.

What I claim is:

An alloy comprising chromium 15% to 60%; phosphorus 3% to 20%; silicon 4% to 6%; the balance being iron.

. MARVIN J. UDY.