US2121057A - Arsenic iron alloy - Google Patents

Description

Patented June 21, 1938 UNITED sTArss 2,121,051 PATENT OFFICE ARSENIO IRON ALLOY Earle C. Smith, Cleveland Heights, and George '1. Motok, Massillon, Ohio, assignors to Republic Steel Corporation, Cleveland, Ohio, at corporation of New Jersey No Drawing. Application December 6, 1937, Serial No. 178,341

4 Claims.

'10 added elements which make them highly resistant to corrosion. An example of this class is stainless steel. The second class includes com- I positions which are only mildly resistant to corrosion, due to the presence of impurities, but which possess relativelylong life under corroding influences by reason of a more or less uniform dispersion of the impurities in finely divided particles. Thus, while the metal corrodes it does so slowly and uniformly as compared with the same metal in which the impurities are present in segregated form and where the corrosion is localized with the formation of pits or holes which soon make the article of little or no value. An example of this class is the iron of the Charis Patent No. 1,355,589.

In our copending application Ser. No. 119,264 filed January 6, 1937, we have pointed out our discovery that nitrogen in proper form and amount is not an element to be avoided, but in 30 fact can be used to confer desirable characteristics on corrosion-resisting irons or steels of certain compositions. In that application it was pointed out that the presence of nitrogen and phosphorus in certain specified amounts conferred certain desirable characteristics on such irons.

Our present invention is based on the discovery that, contrary to generally accepted theory, arsenic in proper form and amount is not an element to be avoided, but can in fact be used to confer desirable characteristics on irons of the second above mentioned class in the presence of nitrogen in certain amounts and nickel or copper, or both nickel and copper, in certain amounts. 45 It has been generally accepted theory heretofore, thatarsenicin-amounts of .05% or more in steel had a detrimental effect on the steel because it was thought that the arsenic affected the physical properties, particularly by causing embrittlement 50 and reduction in resistance to impact.

We have been able to make low carbon steels containing nitrogen and between about 005% and about 50% of arsenic without any adverse effects on the physical properties of the steel traceable to arsenic. Moreover, some steels have exhibited a marked improvement in resistance not onlyv when subjected to ordinary atmospheric or water corroding influences, but also when subjected to sulphuric acid or its fumes.

80 Articles to-be ed during use to corroding conditions and embodying the present invention are typified by the following analyses:-

Percent v Carbon .02 to .15 Manganese .01 to .50 Nickel .10 to .75 Copper .20 to 1.50 Arsenic .005 to .50 I Nitrogen .005 to .20

It will be understood that the remainder is iron with the usual amounts of impurities, including phosphorus, sulphur and the like,.which are ordinarily present in low carbon steels of the foregoing range of analyses.

A preferred range of analyses within the foregoing limits is as follows:-

Percent Carbon. .02 to.10 Manganese .01 to .25 Nickel .10 to .45 Copper n .20 to.90i Arsenic .05 to .50 Nitrogen "a .005 to .05 A preferred specific composition is as follows:--

Percent Carbon... .05 Manganese .08 Nickel .25 Copper .65 Al'senfc .15 Nitrogen .03

We have found that when nickel and copper are present in the ratio of about 1 to 2 and within the limits above specified, the detrimental effects heretofore blamed on arsenic are not evident. As the analyses indicate, the amounts of copper and nickel should vary with the amount of arsenic present, 1. e., as the amount of arsenic increases the amounts of nickel and copper should increase, but preferably the 1 to -2 ratio of nickel to copper should be maintained.-

It is not essential that the nickel and copper should both be present with the arsenic and ni-' trogen. For example, copper alone may be used in amounts which do not adversely affect the steel, as in the tendency to produce cracks, but which will prevent the arsenic from having any detrimental efiects on the steel. Nickel may also be used,in the absence of copper, for preventing the detrimental effects of arsenic, but is higher in price than copper. When copper and nickel are both present, the cost is kept within reasonable bounds and all tendency to cracking of the steel incident to high amounts of copper is avoided. Furthermore, the copper and nickel are completely soluble in each other within the amounts here specified. Hence, we prefer to use both nickel and copper in about the ratio of 1 to 2 and within the limits specified in the foregoing analyses in steels containing arsenic and nitrogen in the amounts there specified.

We believe that when nitrogen within the foregoing limits is present, preferably in the form of more or less stable nitrides, in the foregoing compositions, it increases the resistance of articles composed of such compositions to mildly corroding influences and prolongs the life of such articles. We believe that these characteristics are traceable to the existence of nitrides and possibly of other metals which are in the composition in the form of minute more or less uniformly distributed needles or particles which in themselves are highly resistant to corrosion and which serve as anchors to which may adhere iron oxide which forms during corrosion. These nitrides and the arsenic compounds apparently form a film which may be retained as a protective coating over the surface portions of the iron and which is more or less resistant to corrosion. Such a film protects the iron from continued contact with the corroding agent and hence improves the resistance and prolongs the life of articles made from such iron compositions.

The nitrogen is believed to exert a dispersing effect on the arsenic and thus to insure the subsequent formation of a protective film, containing arsenic compounds such which is more or less uniform on posed to corrosive action.

The presence of copper and nickel is believed to have the effect of preventing segregation of arsenic compounds and exerting a dispersing effect thereon.

the surfaces ex- In practicing the present invention an iron or steel may be made in the usual manner, as in an electric furnace or in an acid or basic open hearth furnace, or in a Bessemer furnace, and/or converter. Such iron or steel should contain between about .02% and about..15% of carbon, between about .01% and about .50% manganese, and the usual amounts of ordinary impurities, such as phosphorus, sulphur and the like. nickel and arsenic may be added to such an iron or steel to bring the contents thereof within the limits specified in the foregoing analyses. Such additions may be accomplished by using the proper amounts of arsenides of metals such as nickel, copper, magnesium and iron. These metallic arsenides may be added to the steel in the furnace or in the ladle, or even when the molten metal is being poured into the ingot molds.

The arsenic should be added in the form 0 metallic arsenides but it is not essential that the nickel and copper to be added should be in the form of arsenides. They may be added in any suitable form.

Nitrogen in the amounts specified in the foregoing analyses may be brought into the iron or steel by throwing into the ingot molds, when the molten metal is being poured from the ladle into such molds, a quantity of a suitable nitrogen material sufiicient to insure the presence of between about .005% and about .20% of nitrogen as stable metallic nitrides in the cold ingots. Alternatively, the nitrogen may be added either in the furnace or in the ladle.

Nitrogen bearing materials which have been found to be suitable for the present purpose,- include metallic materials such as nitrides of copper or iron, cyanides and cyanamids of the alkali metals and alkaline earth metals and urea or other organic compounds containing nitrogen. The alkali and alkaline earth cyanides or cyas metallic arsenides,

Copper.

anamids are quite useful for this purpose. For example, calcium cyanamide is satisfactory both because of its nature and its low cost, and also because the residue remaining after ithas decomposed and liberated nitrogen is beneficial to the iron. Such residues are inert under corroding conditions and hence may serve as anchorages for films of iron oxides which protect underlying portions of the iron from contact with corroding substances. The addition of about five pounds of calcium cyanamide per ton of iron will carry a sufilcient present purposes.

In order to insure retention in the iron of the desired amount of nitrogen, it is preferable to have ingredients present in the iron which will act as nitrogen fixers, i. e., elements which will readily combine with nitrogen liberated in the iron and form stable nitrides. Several metals have been found to be elfective for this purpose, including titanium, vanadium, zirconium, columbium and tantalum. Silicon, aluminum, boron and beryllium are also good nitrogen fixers. Small amounts of one or more of these several elements may be used in amounts suihcient to combine with and retain in the iron nitrogen within the limits of about .005% and about 2%.

. Having thus described the present invention so that those skilled in the art may practice the same, we state that what we desire to secure by Letters Patent is defined in What is claimed.

What is claimed is:

.1. An iron article to be exposed during use to corroding conditions, containing between about .02% and about .15% of carbon, between about .01% and about .50% of manganese, between about .10% and about .75% of nickel, between about .20% and about 1.50% of copper, the nickel and copper being present in the ratio of about 1 to 2, between about .005% and about .50% of arsenic, between more than .02% and about 20% amount of nitrogen into the iron for the of nitrogen, the remainder consisting of iron containing small amounts of ordinary impurities.

2. An iron article to be exposed during use to corroding conditions containing between about .02% and about .10% of carbon, between more than .02% and about .10% of nitrogen, between about '.005% and about .50% of arsenic, between about .10% and about .75% of nickel, between about 20% and about 1.50% of copper, the nickel and copper being present in the ratio of about 1 to 2, between about .01% and about .50% of manganese, the remainder consisting of iron containing small amounts of ordinary impurities.

3. An iron article tobe exposed in use to corroding conditions containing between about .02% and about .10% of carbon, between more than .02% and about .20% of nitrogen, between about .05% and about .50% of arsenic, between about .10% and about .75% of nickel, between about .20% and about 1.5% of copper, the nickel and copper being in the ratio of about 1 to 2, between about .01% and about .50% of manganese, the remainder consisting of 'iron containing small amounts of impurities.

4. An iron article to be exposed during use to corroding conditions containing about .05% and about .10% of carbon, about .03% of nitrogen, about .15% of arsenic, about 25% of nickel, about .65% of copper, between about .01% and about .50% of manganese, the remainder consisting of iron with small amounts of impurities.

EARLE C. SMITH. GEORGE T. MOTOK.