US1890548A - Prealloys - Google Patents

Description

Patented Dec. 13, 1932 PATENT OFFICE JOSE] HOVAK AND ROMAN KESSELBING, QB ODERBEBG, CZECHOSLOVAKIA rnEA'LLoYs "no Drawin .Driginal application filed April 17, 1930, Serial No. 445,198, and in Germany March so, 1929.

Divided and this application filed July 28, 1931. Serial No. 553,681.

Our invention relates to alloy steels and is particularly useful in connection with the production of rust-proof or non-corrodible steel. The steel produced in accordance with the present invention is clearly distinguished from the allo steels hitherto manufactured by its articfi ar composition, the particular metho of producing the same and by its inherent particular properties or concomitant characteristics. The most important advantages of our improved alloy steel reside, on the one hand, in the comparatively low manufacturing cost and the moderate settingprice of the steel and, on the other hand, in the particular qualification thereof for the manufacture of referably seamless tubes for various uses and the like.

As regards the peculiar and characteristic composition of the improved alloy steel, the same is practically free of silicon and contains only a very low proportion, that is .015 to .04 per cent of sulphur, a similarly low pro-' portion, that is .005 to .003 per cent of phosphorus and a low percentage of carbon rangmg from .03 to .10 per cent only, while the alloying ingredients are chromium, copper, nickel and tungsten.

As the percentage of sulphur: and phosphorus is very low and silicon is not at all contained in the improved alloy steel, only a small percentage of the said expensive alloy."

' ing ingredients is required for t securing the special properties desired, the amount of chromium in the alloy steel ranging from say .1 to 1 percent, that of copper ranging from .25 to .5 per cent, that of nickel ranging from .04 to .25 per cent, while the proportion of tungsten amounts to between .01 and .05 .per cent, depending upon the dees of im rovement in physical properties esired in t e particular case.-

' The alloy steel according tothe present invention is produced preferably in the basic Siemens-Martin furnace with theaid of regenerative gas and at the usual normal charge purpose-pf,

ing steps. In the following example special data as regards the charge of the furnace are given: 2000 kg. of grey Martin pig-iron 3000 kg. of white Martin pig-iron, 2500 kg. 0 special crude iron poor inphosphorus and 1800 kg. of scrap are supplied to the furnace and during the melting process the usual amounts of lime are added to the charge, while decarbonization is accomplished to about .03 per cent. Contamination and cooling of the bath is to be avoided and the expensive alloying ingredients such as chromium, copper, nickel and tungsten, are added to the liquid steel bath in the form and manner as hereinafter described. As the said four metallic elements are preferably added, according to the present invention, in the form of an alloy initially or previously produced for the purpose, the said alloying ingredients may be supplied to the charge at 66 any time irrespective of the phase of the melting process. The addition of the alloying ingredients in the form of the said initial or special alloy prevents the metallic elements from going partially into the slag so 70 that no losses of metal can occur not even in the case that the said alloy will be added to the steel bath prior to the complete de asification and deoxidation of the latter. l referably, however, the alloy will not be added to the bath prior to the complete degasification of the latter.

The initially prepared alloy of the four metals to be added to the steel bath according to the present inventioncontains, as a base, a batch of 'iron which is free of phosphorus, sulphur, silicon and manganese and which contains 20 to30 per cent of chromium,

5 to 6 per cent of tungsten, 6 to 10 per cent of nickel, 10 to 15 per cent of copper, and 2.5 to 3 per cent of carbon. The latter, however,

is not allowed to be free carbon of graphitic nature but necessarily must be of bound carbiiiic character in order to ensure best resu ts.

In producing the said initial alloy we mix in a graphite crucible; white speclal pig-iron which is practically free of phosphorus, sulphur, silicon and manganese, wlth high-per cent ferro-tungsten, high-per cent ferro-chromium, pure nickel and copper or copper-alu minium, and we melt the mixture down to obtain a homogeneous alloy. The crucible is kept closed during the melting oeration whereupon the slag is removed from t e molten metals and the latter are stirred, if required, before they are poured into moist sand for the molding purpose. The alloy thus produced possesses a high percentage of chromium, tungsten, nickel and copper, and has a fine-radiate, dense, white fracture and a ledeburitic structure. In followin the above described steps of the process 0 producing the alloy the 3 per cent of carbon therein are of carbidic nature, that is in the form of carbides of the metallic elements iron, chromium, tungsten, nickel and copper.

An explanation of the term ledeburitic structure will be found in the following publication Leon Cammen, Principles of Metallurgy of Ferrous Metals, New York, 2nd edition, 1926, the American Society of Me chanical Engineers. Page 95 of this publication contains a solidification diagram of the iron showing the conditions under which ledeburitie is crystallized out. Page 97 contains a figure 28 showing a micro photograph of the ledeburitic structure, on page 98 above it is distinctly stated that the name ledeburitie originates from a proposal of Wiist.

The alloy initially produced according to the present invention mainly serves the purpose of'making rust-proof alloy steels, but the valuable particular properties of this alloy render the'same also useful and suitable for sundry other purposes where the comparatively high price is not a bar. Thus the alloy may be used for making special castings or cast articles therefrom which when worn out may be further utilized for the original or main purpose of producing rust-proof al- 10y steels.

Instead of the described four metallic elements several other elements such as zirconium, aluminium, boron, beryllium and molybdenum, may be used for producing the initial alloy and subsequently alloy steels of the character described. In such a case also care should be taken to keep the steel free of silicon and the percentage of phosphorus and sulphur very low as herein indicated. In producing the alloy steel the alloying ingredients are also to be added in this case in the form of an initially prepared alloy of ledeburitic structure and containing 3 per cent of carbon in carbidic form, just as de scribed with reference to the metals chromium, tungsten, etc.

An alloy steel comprising chromium,

- form in the various countries.

nickel, copper and tungsten and which is free of silicon and poor in phosphorus, sulphur and carbon, as herein described, possesses the following desirable characteristics, to wit:

(a) a specific gravity of 7.7 to 7.85;

(b) a melting point of 1520 (3.;

(0) almost the same heat conductivity as pure iron;

(41) an electric resistance which is somewhat greater than that of soft iron;

(e) the alloy is magnetic;

(f) as regards the structure, ferrite-perlite prevails when the steel is in a soft red-hot condition, with the dissolved copper transformed into mixed iron-copper crystals and of slight chrom um-tungsten carbidic character. Crystallization of dense fine-granular character throughout; when properly hardened Martensite color mainly prevails which, however, has a bluish tint when the hardened steel is polished;

(g) a coefiicient of expansion just as that of ordinary soft steel;

(h) a cutting capacity like that of ingot- 1ron;

(i) a modulus of elasticity of 20700 kg/mm a limit of stretching strain of 37 to 40 kg/min a relative elongation 1=5d 25 to 29, and a notching tenacity of 30 m. kg/cm all of which to be understood with the steel in red-hot condition.

In explanation it may be stated that the elongation A1 taking place after the breaking of atest rod is regarded as an elongaton (rupturing elongation) with respect to the original measuring length 1 It is usually (at least in Germany) indicated in hundredths of the original measuring length The elongation is composed of the uniform elongation of the measuring length up to the maximum load and the resulting local elongation of the constricted steel element, on the basis of a circular cross sectional test. The elongation is determined with our steel according to the standards 1605 of the German industry at the so called short standard test rod with a diameter d=20 mm. and a measuring length 1 100 mm.; hence, a measuring length ratio of 1:d=5; a modulus of elasticity of 25% resulted therefrom.

The modulus of elastcity lzd is not uni- In Great Britain (British Engineering Standard Association) the ratio of elongation is determined in the following manner: the rod is the round rod of 2" length; diameter 0.564 0.798 or 0.977.; measurng length 1: ($3.55, 3.77 or 3.58.

Other valuable properties of the improved alloy steel are especially useful in case of machining operations. or alloy steels produced as. herein disclosed; can readily be punched and stamped, welded, pressed, cut,

bored and forged and without the application of heat or fire, where required or feasible, and the finely granular structure of the steel or the resistance to the influence of corroding or rust-producing agents thereof, will never be impaired or reduced by such machining or working operations. In particular alloy-steels of this improved sort are especially adapted for use in drawing or rolling tubes and pipes for various purposes, and they are capable of being hardened as easily as other kinds of ingot-iron poor in carbon with the result, however, that the grain of the structure will be increased thereby to a. certain degree. v

As regards the rust-proof quality that is the resistance of the steel to the action of corroding or oxidizing agents, we have found that a smooth brown coating forms on the steel when exposed to the influence of the atmospheric air, and this coating protects the surface of the steel and prevents the latter from further corrosion and damage. Furthermore We have found that the improved alloy steel stands the action of diluted acids and is not seriously corroded by diluted nitric acid, sulphuric acid, hydrochloric acid, acetic acid, oxalic acid, or by humic acds, while Water conta ning carbonic acid and water ,of natural Wells have no corroding cfiect on the steel either. \Vhen heated to a red-hot condition, only a thin, dense and smooth oxide layer or film (scale) forms on the steel which adheres to the steel surface with greater tenacity than in case of ingotiron.

iron is the base, the content of chromium being between 20 and 30 per cent, tungsten between 5 and 6 per cent, nickel between 6 and 10 per cent, copper between 10 and 15 per cent and the content of carbon of carbidic character between 2% and 3 per cent.

2. An article of manufacture, a rust-proof, non-corrosive alloy consisting of 20 to 30 per cent chromium, 5 to 6 per cent tungsten, 6 to 10 per cent nickel, 10 to 15 per cent copper, 2 to 3 per cent carbon of carbidic character and iron as the base and which contains only traces of phosphorus, sulphur, silicon and manganese; I p

In testimony whereof we aflix our signatures.

J OSEF NOVAK. ROMAN .KESSELRING.

Obviously alloy steels produced in accord- I pipes for boilers, boiling tubes, smoke tubes,

socket pipes, water pipes, conduit fittings or implements, plates and other articles for use in naval architecture and railroad cars, engine bonnets for automobiles, stove and chimney equipments and so on.

From the foregoing, it is believed, that the advantages and novel features of our invention will be readiiy understood and, therefore, further detail description is deemed unnecessary. We do not, however, desire to be limited to the exact details of the invention described and we aim in the appended claims to embrace all modifications falling fairly Within the scope of our invention.

What we claim is:

1. A pre-alloy for producing rust-proof, non-corrodible alloys, which consists of the elements iron, chromium, tungsten, nickel and copper having a ledeburitic structure and