US1876467A - Josef novak and roman kesselbing - Google Patents

Description

Patented Sept. 6, 1932 UNITED STATES,

PATENT OFFICE ALLOY No Drawing. Application filed April 17, 1930, Serial No 445,198, and in Germany March 30, 1929 I 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 by itsparticular composition from the alloy steels hitherto manufactured, the particular method 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 selling-price of the steel and, on the other hand, in 'the particular qualification thereof for the manufacture of seamless tubes and for various other uses.

As regards the peculiar and characteristic composition of the improved alloy steel, the

same is practically free from silicon and contains only very low proportions of sulphur,

' phosphorous and carbon, that is .015 to .04per cent of sulphur, .005 to .003 per cent of phosphorus and .03 to .10 per cent of carbon, while'the alloying ingredients are chromium, copper, nickel and tungsten. v 7 As the percentage of sulphur and phosphorus is very low and silicon is in the improved alloy steel, only asmall percentage of the said expensive alloying ingredients is required for the purpose of securing the special properties I desired, the amount of chromium in the alloy steel ranging from .1 to 1 per cent, 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 degree of improvement in physical properties desired in the particular case.

The alloy steel according to the present invention is produced preferably in the basic Siemens-Martin furnace with the aid of regenerative gas and by the usual normal charging steps. In the following example special data as regards the charge of the furnace are given: 2000 kg. of grey Martin pigiron, 3000 kg. of white Martin pig-iron, 2500 kg. of special crude iron poor in phosphorus and 18000 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 c00ling of the bath is to be avoided and the expensive alloying ingredients such as chromium, I .7

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, ac-

cording to the present invention, in the form so of an alloy initially or previously produced for the purpose, the said alloying ingredients may be supplied to the charge at any. time irrespective of the phase of the melting proccess. The addition of the alloying ingre- 05 dients in the form of-the said initial or special alloy prevents the metallic elements from going partially in to the slag so 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 degasification and deoxidation of the latter. Preferably, how v ever, 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 invention contains,-as a base, a batch of iron. which is free of phosphorus, sulphur, silicon and manganese and which contains 20 to 30 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 carbidic character in order to ensure best results.

In producing the said initial alloy we mix in a graphite crucible, while special pig-iron which is practically free of phosporus, sulphur, silicon and manganese, with high-per cent ferro-tungsten, high-per cent ferro chromium, pure nickel and copper or copperaluminium, and we melt the mixture down to obtain a homogeneous alloy. The crucible is kept closed during the melting operation whereupon the slag is removed from the molten metals and the latter are stirred, if required, before they are poured sand for the molding purpose. The alloy thus produced prossesses a high percentage of chromium, tungsten, nickel and copper, and has a fine-radiate, dense, white fracture and a ledeburitic structure. In following the above described steps of the process of producing the alloy the 3 per cent of carbon therein, are of carbidic nature, that is in the form or carbidesof 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 Mechanical Engineers. Page 95 of this publication contains a solidification diagram of the iron showing the conditions under which ledeburite is crystallized out. I 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 ledeburite 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

a 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 alloy steels.

linstead of the described four metallic elements several other elements such as zir- In producing conium, 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 andthe percentage of phosphorus and sulphur very low as herein 1ndicated.

ingredients are also tobe added in thiscase in the form of an initially prepared alloy of.

ledeburitic structure and containing 3 per cent of carbon in carbidic form, just as described with reference to the metals chromium, tungsten, etc.

An alloy steel comprising chromium, nickel, copper and tungsten and which is free of silicon and poor in phosphorus, sulinto moist the alloy steel the alloying phur 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 C.;

(0) Almost the same heat conductivity as ure iron; (d) An electric resistance which is somewhat greater than that of soft iron;

(6) The alloy is magnetic;

(f) As regards the structure, ferriteperlite prevails when the steel is in a soft redhot condition, with the dissolved copper transformed into mixed iron-copper crystals and of slight chromium-tungsten-carbidic character. Crystallization of dense finegranular character throughout; when properly hardened Martensite colour 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; 7

(h) A cutting capacity like that of ingotiron;

(i) A kg/mm a limit of stretching strain of37 to 40 kg/mm 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 a test rod is regarded as an elongation (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 elon gation 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 socalled short standard test rod with a diameter d=20mm 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 elasticity 1:Z is not uniform in the various countries. 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; measuring'length 1:d3.55, 3.7 7 or 3.58.

Other valuable properties sit the improved alloy steel are especially useful in case of machining operations. F or alloy steels produced as herein disclosed, can readily be modulus of elasticity of 20700 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.

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 asmooth browncoating 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 phosphorus up to 0.005 percent and sulphur up to 0.0% percent.

In testimony whereof we have signed our names to this specification.

JOSEF NOVAK. ROMAN KESSELRING.

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 acids, while water containing carbonic acid and water of natural wells have no corroding effect-on the steel either. When heated to a red-hot condition, only a thin, dense and smooth oxide layer of film- (scale) forms on the steel which adheres to the steel surface with greater te nacity than in case of ingot-iron.

Obviously alloy steels produced in accordance with the present invention, are especially "fore, further detail description is deemed unnecessary. We do not, However, desire'to be limited to the exactdetails of the invention described andwe aim in the ap ended claim to embrace all modifications alling fairly within the scope of our invention.

Whatweclamis:- A rust-proof, silicon-free, non-corrodible steel'alloy containing from 0.1 to 1 percent chromium, from 0.25 to 0.5 percent copper,

from 0.04120 0.25 percent nickel,fr'om 0.01 to 0.05 percent tungsten and carbon from 0.03 to 0.10 percent, and. the balance substantially all iron with the exception of impurities as