US2179114A - Method of making seamless tubes from columbium containing austenitic chromium nickel alloy steel and product thereof - Google Patents

Description

Patented Nov, 7,1939;

PATENT OFFICE METHOD OF MAKING SEAMILESS TUBES FROM COLUMBIUM CONTAINING AUSTEN- ITIC CHROIVIIUIW NICKEL ALLOY STEEL. AND PRODUCT THEREOF Vere B. Browne, Brackenridge, Pa., assignor to Allegheny Steel Company, a corporation 0 Pennsylvania No Drawing. Application September 12, 1935, Serial No. 40,346

'1 Claims.

This invention relates to a method of makin seamless tubes from columbium-containing austenitic chromium nickel alloy steel and to seamless tubes therebyproduced, the present application being a division of my co-pending application Serial No. 17,154, filed April 18, 1935.

- In making seamless tubes from austenitic chromium nickel steels, such steels are heated and pierced, in the form of billets, in the temperature range of 2100-2300 Fahrenheit. Even when their carbon content is below 0.07%, the

- austenitic chromium nickel steels of the 18-8 type present no especial difflculty in the production of seamless tubes.

When, however, there is an increase of the position.

As the nickel and chromium are increased the delta ferrite constituent iscorrespondinglyformed at progressively lower temperature. It is, however, impractical and well-nigh impossible to pierce the starting material at a temperature of 2000 F. or lower because the usual piercing mills do not have sufiicient power to force a hole through the billet or starting material at these low temperatures and even if they had, there is no known piercing point of sufiicient strength at these temperatures to effect the piercing operations.

Columbium, as well as various rare elements,-

have been added for stability, but these, including columbium, cause the formation of delta ferrite at temperatures considerably below those temperatures at which delta ferrite is formed in steels of the same composition whichcontain no columbium or other of the rarer elements which have been used. For this reason, commercial and satisfactory seamless tubes cannot be made even.

when the alloy contains columbium, except in accordance with my present invention.

I have discovered that I can successfully hot work columbium-bearing 18-8 and also successfully produce seamless tubes therefrom provided the composition, excluding the columbium, is

rationally proportioned in a certain manner to be hereinafter set forth and under which circumstances delta ferrite is not formed. at temperatures up to 2300 F. so that seamless tubes can be readily produced by conventional methods in the same manner and at the same temperatures as from alloys or steels containing no columbium. I

It is accordingly an object of the present invention to provide an austenitic chromium nickel iron alloy or steel containing columbium which can be readily hot worked as, for example, by rolling, forging or piercing.

Another object of my invention is the production of seamless tubes from columbium-containing austenitic chromium nickel ironalloys without the formation of delta ferrite within the ordinary piercing temperature ranges.

A further object of my invention is, in an austenitic chromium nickel iron alloy or steel containing columbium, to so proportion certain of the elements thereof, particularly the chromium and nickel contents, as to avoid the difficulties and problems, which hitherto confronted the art.

make possible the production of physically perfect seamless tubes from a columbium-containing austenitic chromium nickel iron alloy or steel in the same manner in which these tubes are produced' from alloys or steels which do not con;- tain columbium, i. e., by standard commercial methods.

Other and further objects and advantages reside in the various details to be'hereinafter set forth and such will be understood by those skilled in this art or will be apparent or pointed out hereinafter.

I have discovered that if I add approximately .3-1% of columbium to the austenitic chromium nickel iron alloys or steels containing about 16-18% of chromium, about -11% of nickel 'and not over about .12% of carbon, with the balance substantially all iron. except for the usual contaminants in common amounts, and maintain such a relationship between chromium and nickel that the ratio is not over 2:1 while maintaining carbon about to the amount of columbium, I produce material which can be readily forged, rolled and worked without tearing, breaking, etc. The material can therefore be worked or treated according to standard commercial practice, a thing which has hitherto been practically impos- A still further object of my' invention is to ,sible or exceedingly difficult in connection with 1 Chromium Total cliro Chro- Colum- Carbon Nickel nlckel mium-l- [mum bium ratio nickel 15 1 090 17. 76 8. 88 1. 055 2. O 26. 64 2 08 19. 93 8. 97 l. 82 2. 22 28. 9 3 076 17. 3 7. 67 94 2. 26 24. 87 4 084 17. 09 9. 96 63 l. 71 27. O

I, therefore, may state as a general proposition that my invention comprises a seamless tube composed of an austenitic chromium nickel iron alloy or steel containing about .3-1% of columbium in which the ratio of chromium to nickel is not more than 2 to 1 and in which the carbon is preferably less than .12%. Compositions within this definition can be successfully hot worked and seamless tubes can be commercially produced by the conventional piercing operations and within the conventional temperature range of 2100 to 2300 F. The advantage of the capacity of my alloy to produce satisfactory commercial forms by hot working such as rolling or forging operations or by hot piercing are eviden to those versed in this art.

I have discovered that if in an austenitic chromium nickel iron or steel alloy columbium is incorporated within the limits of about .3 to 1% with carbon preferably under approximately when the ratio of the amount of chromium to the amount of nickel is not over 2 to 1 there is practically no delta ferrite produced when billets of this material are formed by rolling or working and pierced up to 2300 F., so that satisfactory seamless tubes can be produced from such material by standard commercial practice. This principle is illustrated by compositions Nos. 1 and 4 supra in which it is apparent that the ratio of chromium to nickel is not over 2 to 1. On the contrary, in compositions Nos. 2 and 3 the ratio of chromium to nickel is respectively 222 to 1 and 2.26 to l, in both cases the ratio, therefore, being more than 2 to 1. Compositions 2 and 3 show delta ferrite at temperatures as low as 2100 F. and even lower and hence will not produce commercial seamless tubes by conventional commercial practice.

I am aware that the use of columbium in an austenitic chromium nickel iron alloy or steel is not broadly new with me but, remembering the defects and difficulties above set forth, it is apparent that I have made it possible for the art to reduce, by hot rolling and forging operations, ingots without excessive breakage and to prepare seamless tubes commercially by standard methods and from an austenitic alloy containing columbium by limiting the ratio of chromium to nickel such that it is not more than An alloy as described containing .3-1% columbium shows upon microscopical examination that, although columbium and carbon apparently combine to form columbium carbides, the 5 carbides are not rejected to the grain boundaries but on the contrary are uniformly distributed through the grains themselves. Because of this dispersion the new properties and charactertistics are obtained.

In making seamless tubes from the columbiumcontaining alloy or steel above described, I form billets or other suitable starting pieces in any known or desired manner and then pierce the billets or other starting pieces according to standard commercial practice, that is, at 2100-2300 F., with the usual piercing points. No breaking or tearing of the tubes occurs because there is no substantial formation of delta ferrite under the conditions noted. I have thus for the first time made it possible to produce, by standard commercial practice, columbium-containing austenitic alloy seamless tubes and to produce them without any material percentage of seconds or defective tubes.

The foregoing is presented as exemplary and not as limitative, the scope of the invention being rather that set forth by the subjoined claims. It is clear that I may make certain modifications, variations, omissions and/or substitutions so long as I remain within the principles hereinabove set forth and my invention not only applies to seamless tubes but to other articles of manufacture wherein the principlesof the present invention find application. By the same token, my invention includes a method for producing such seamless tubes wherein, however, the composition used falls within the-principles and scope of the present invention. I am, moreover, not restricted to columbium only as I may utilize equivalents thereof or any other suitable element in the same group of Mendelejeffs periodic arrangement of the elements.

I do not claim in this application the columbium containing austenitic chromium nickel steel alloy per so since such forms the subject matter of my companion application Ser. No. 17,154, filed April 18, 1935. Nor do I claim in this application the method of making welded products and the products thereby produced since such forms the basis of my companion application Ser. No. 40,276, filed September 12, 1935.

What I claim as new and desire to secure by Letters Patent is:

1. The method of making seamless tubes comprising rolling or working ingots to form billets from an austenitic chromium nickeliron columbium steel or alloy containing about 16-18% chromium, about 85-11% nickel but where the ratio of chromium to nickel is not over 2:1, and about .3-1% columbium, the balance being substantially all iron except for the usual contaminants in common amounts, piercing the billets at 2100-2300 F. to form the tubes and thereafter finishing the tubes in required manner.

2. The method of making seamless tubes comprising rolling or working ingots to form billets from an austenitic chromium nickel iron columbium steel or alloy containing about 17.76% chromium, about 8.88% nickel, about .09% carbon and about 1.05% columbium, the balance of the steel or alloy being substantially all iron except for the usual contaminants in common amounts, the ratio between the chromium and nickel being not over 2:1, piercing the billets-at 2100 to 2300 F. to form the seamless tubes and thereafter finishing the tubes as required.

3. The method of making seamless tubes comprising rolling or working-ingots to form billets from an austenitic chromium nickel iron columbium steel or alloy containing about 17.09%

chromium, about 9.96% nickel, about .08% carbon and about .63% columbium, the balance of the steel or alloy being substantially all iron except for the usual contaminants in common amounts, the ratio between the chromium and nickel being not over 2:1, piercing the billets at 2100 to 2300 F. to form the seamless tubes and thereafter finishing the tubes as required.

4. The method of making seamless tubes free from delta ferrite formation which comprises making a heat of austenitic chromium nickel columbium steel, adjusting the composition of the heat so that the chromium content thereof falls between about 16% and 18%, the nickel content thereof falls between about 8.5% and 11%, the columbium content thereof falls between about 0.3% and 1% and the carbon content thereof is not over about .12%, adjusting the relative chromium and nickel contents within the above limits so that Cr/Ni is not over 2:1, casting an ingot. having an analysis responding to said heat, forming billets from such ingot, piercing the billets at 2100-2300 F. to form tubes and finishing the tubes as required.

5. A seamless tube composed of an austenitic steel or alloy containing about 16-18% chromium,

about -11% nickel, the ratio of chromium to nickel being not more than 2: 1, and about 0.3-1% columbium, carbon being not over about 0.12%

about 8.88% nickel, about 0.09% carbon and about 1.05% columbium, the balance being substantially all iron except for the usual contaminants in common amounts, the alloy steel being characterized by the fact that the ratio of chromium to nickel is not over 2:1, the tube being characterized by freedom from delta ferrite despite its formation by piercing at temperatures which normally produce delta ferrite.

7. A seamless tube'composed of an austenitic steel or alloy containing about 17.09% chromium, about 9.96% nickel. about 0.08% carbon and about 0.63% columbium, the balance being sub-' despite its formation by piercing at temperature which normally produce delta ferrite.

, VERE B. BROWNE.