US3656917A

US3656917A - Steel alloy tubes

Info

Publication number: US3656917A
Application number: US815215A
Authority: US
Inventors: Osamu Kikkawa; Akira Kambayashi
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1966-09-10
Filing date: 1969-04-10
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18
Also published as: US3554734A; GB1146785A; DE1558549A1

Abstract

Low carbon steel alloy tubes of high tensile strength. The steel alloy contains less than 0.23% carbon, less than 0.5% silicon, from 1.00 to 1.50% manganese, less than 0.040% phosphorus, less than 0.040% sulfur, less than 0.30% copper, less than 0.50% chromium, from 0.010 to 0.080% aluminum, and the remainder of iron and impurities in an amount and variety which do not impair the desired characteristics of the alloy. There is preferably not less than 0.20% silicon and from 1.00 to 1.35% manganese. This steel after being rolled into a steel plate is welded into a steel tube of high tensile strength. Also, the steel alloy is a killed steel and in particular an aluminum killed steel.

Description

[73] Assignee:

United States Patent Kikkawa et al.

[54] STEEL ALLOY TUBES [72] Inventors: Osamu Kikkawa; Akira Kambayashi, both of Yokohamashi, Japan Nippon Kokan Kabushiki Kaisha, Tokyo, Japan [51] Int. Cl ..B2lc 37/00 [58] Field of Search ..75/124, 125; 29/193 [5 6] References Cited UNITED STATES PATENTS 8/1890 Blakey ..29/193 [151 3,656,917 [4 1 Apr. 18, 1972 Breeler Primary Examiner-l-lyland Bizot An0rneySteinberg and Blake [5 7] ABSTRACT Low carbon steel alloy tubes of high tensile strength. The steel alloy contains less than 0.23% carbon, less than 0.5% silicon, from 1.00 to 1.50% manganese, less than 0.040% phosphorus, less than 0.040% sulfur, less than 0.30% copper, less than 0.50% chromium, from 0.010 to 0.080% aluminum, and the remainder of iron and impurities in an amount and variety which do not impair the desired characteristics of the alloy. There is preferably not less than 0.20% silicon and from 1.00 to 1.35% manganese. This steel after being rolled into a steel plate is welded into a steel tube of high tensile strength. Also, the steel alloy is a killed steel and in particular an aluminum killed steel.

6 Claims, No Drawings STEEL ALLOY runes CROSS REFERENCE TO RELATED APPLICATION This applicationis a divisional of our application Ser. No.

683,720, filed May 16, 1967, for Steel Alloy and Tube Manufactured Therefrom now U.S. Pat. No. 3,554,734.

BACKGROUND OF THE INVENTION The present invention relates totubes made of low carbon steel alloys of high tensile strength. While the alloys have many possible uses, the same are particularly useful for the manufacture of welded steel tubes. The alloys which are used in manufacturing the steel tubes according to the present invention are of X-60 high tensile strength.

At the present time there are known steel alloys of X-60 high tensile strength used in the manufacture of steel tubes, but these alloys require as part of their composition columbium or vanadium, or both, in addition to manganese. According to the provisions of API (1966), it is specified that such alloys should contain less than 0.26% carbon, less than 1.35% manganese, less than 0.04% phosphorus, less than 0.050% sulfur, more than 0.01% Cb and more than 0.02% V. In addition it is specified that either one or both of Cb and V should be included in the alloy.

Inasmuch as steel alloys of this type are manufactured primarily according to the semi-killed method, these alloys do not have the fine grain structure of an alloy of high carbon content, and as a result they are required to be rolled under special lowtemperature rolling conditions. As a result the efficiency with which the rolling operations are carried out with conventional alloys of this type are considerably below an ideal rolling efi'lciency. Furthermore, because of the carbon content, which is relatively high, the capability 'of welding the alloy, in the field is poor. Also, because the alloy is a semikilled steel, its strength is not uniformly distributed.

. SUMMARY OF. THE'INVENTION It is accordingly a primary object of the present invention to provide tubes made of steel alloys which avoid the above drawbacks of the conventional steel alloys.-

It is a further objectof the invention to provide tubes made of low carbon steel alloys of high tensile strength, which alloys do not contain relatively expensive columbium and/or vanadium, but instead replaces the columbium and/or vanadium with less expensive substances while at the same time providing an increase inthe desirable characteristics of the alloys.

It is yet a further object of the present invention to provide welded steel tubing made of these alloys and particularly of killed steel, and most preferably aluminum killed steel alloys.

With the above and other objects in view, the present invention mainly comprises tubes made of low carbon steel alloys of high tensile strength, which contain manganese, copper, and chromium, the relatively inexpensive copper and chromium being used to replace the far more expensive columbium and vanadium, while at the same time achieving superior results. This alloy of the invention is rolled into steel plate which is then welded into steel tubing by a suitable welding method such'as the UOE submerged arc welding method. In this way it is possible to provide steel tubes of X-60 high tensile strength, having in fact a tensile strength of more than 78,000 psi. The chemical composition of this low carbon steel alloy of the invention includes less than 0.23% carbon, less than 0.50% silicon, from 1.00 to 1.50% manganese, less than 0.40% phosphorus, less than 0.040% sulfur, less than 0.30% copper, less than 0.50% chromium, from 0.010 to 0.080% aluminum, and the remainder of iron and impurities the quantity and variety of which do not impair the desirable characteristics of the alloy.

' In this way the strength of the low carbon steel alloy of the present invention having the above chemical composition is increased to the desired extent while utilizing inexpensive copper and chromium rather than the far more expensive columbium and vanadium. In addition, the cutting toughness of the alloy is improved and the desired characteristics thereof are stabilized by manufacturing the alloy according to the aluminum killed method.

As compared with conventional alloys of the above type containing columbium and vanadium, the carbon content of the alloy of the invention is substantially reduced so as to improve greatly its weldability. In addition, there is achieved with the alloy of .the invention a fine grain structure which makes it possible to avoid the reduction in efl'iciency of the rolling operations necessarily inherent in the conventional alloys as a result of the temperature controls required due to the critical quantities of the various elements in the conventional alloys.

While the carbon content of the alloy of the invention is less 5 than 0.23 percent, the minimum quantity of carbon is 0.10

percent in view of the value of carbon equivalent.

Inasmuch as silicon is included to provide the required strength for the material, the maximum quantity thereof should be 0.50 percent while the minimum quantity should be 0.20 percent. Otherwise the required strength is not achieved.

As is the case with conventional steel alloys, it is preferred that the quantities of sulfur and phosphorus should be quite low, but it was found that no deleterious effects were noted where the quantities for both of these elements did not exceed 0.040 percent.

Inasmuch as copper if present in an amount. greater than 0.30 percent causes reheat brittleness during the rolling operations while chromium in a presence of more than 0.50 percent will in general result in an increase in the hardness of the material in view of the value of carbon equivalent, resulting in difficulties in connection with welding operations, the composition of the invention contains less than 0.30 percent copper and less than 0.50 percent chromium.

. Because the granulation resulting from the presence of aluminum is not noticeable up to 0.010 percent, whereas cracks in the steel ingot will result where the aluminum is present in a quantity of more than 0.080 percent, the aluminum in the alloy of the invention is maintained between 0.0l0percent and 0.080 percent.

Manganese in an amount of less than 1.00 percent does not provide the required strength while manganese in an amount of more than 1.50 percent impairs the weldabilityof the alloy, in much the same way that chromium impairs the weldability thereof if present in too great an amount. The manganese is maintained between 1.00 and 1.50 percent, preferably from 1.00 to 1.35 percent.

' DESCRIPTION OF A PREFERRED EMBODIMENT The manner in which the present invention brings about the desired objects will be understood more fully from a consideration of the following preferred embodiment of the invention.

In accordance with the invention a steel tube of high tensile strength was manufactured by the above-discussed methods, namely by manufacturing the steel according to the aluminum killed process and then rolling the steel into the form of steel plate. The low carbon steel alloy of the invention contained 0.l5-0.20% carbon, 0.20-0.50% silicon, 1.00-1.35% manganese, 0.10-0.20% copper, and 0.10 and 0.40% chromium.

The strength, cutting toughness, weldability, inequality of strength distribution, anti-corrosive property and similar properties of a tube manufactured according to the submerged With respect to preservation of strength (durability), the tube manufactured with the alloy of the invention and those manufactured with the conventional alloys showed in general the same tensile strength of more than 60,000 psi.

2. Cutting toughness:

The tubes manufactured with the conventional alloys had 50% shear rupture temperature (50% fracture surface transition temperature) of 30 to +40 F., while the alloy steel of the present invention showed an improved 50% shear rupture temperature of 80 to -60 F.

3. Weldability:

The steel alloy of the present invention had a weldability comparable in terms of carbon equivalent (USA) to alloys containing 0.330.49% columbium or 0.35-0.45% vanadium. Thus, without using these latter expensive materials the alloy of the invention achieved weldability which could only be achieved with alloys having relatively large amounts of these expensive materials.

4. Rolling efficiency:

Because of the temperature controls required by the conventional alloys there is a decrease in the rolling efficiency with the conventional alloys on the order of whereas there is absolutely no decrease in the rolling efficiency when rolling the alloy of the present invention.

5. Inequality of strength distribution:

With the convention steel alloys manufactured according to the semi-killed process, the inequality of strength distribution was found to be 6-7 Kglmm while with the steel alloy of the present invention prepared according to the killed process the inequality of strength distribution was reduced to 4-5 Kg/mm.

6. Anti-corrosive property:

A comparison of the alloy of the invention with the conventional alloys showed a marked improvement in the anti-corrosive property. In particular, the extent of corrosion of the steel alloy of the invention was less than 10 percent, and this latter amount represented a marked improvement over the anti-corrosive properties of the conventional alloys.

it is apparent, therefore, that with the present invention it is possible to achieve a low carbon steel alloy of high tensile strength particularly suitable for the manufacture of steel tubes, although equally suitable for the manufacture of other articles, by making use of low carbon steels which have as part of their composition copper and chromium instead of making use of high carbon steels which have as part of their composition expensive columbium or vanadium. Using the low carbon steel of the alloy of the invention greatly improves the weldability as compared to the conventional alloys. in addition, the granulation is brought about by way of the aluminum-killed method used in manufacturing the alloy of the invention instead of during the rolling operations, as has been conventional, so that not only is the efficiency of the rolling operations improved but in addition the degree to which the inequality of the strength is distributed is decreased. It is-therefore possible with the alloy of the invention to achieve articles such as steel tubes having high tensile strength and very high quality while utilizing an alloy and methods which are simple and inexpensive as compared to conventional alloys and methods.

While in the above-described embodiment relates to the production of a particular high tensile strength steel tube, it is to be understood that variations and modifications of the alloy can be made within the limits of the invention without departing from the spirit or scope of the invention. Such variations and modifications are accordingly meant to be comprehended within the meaning and scope of equivalents of theappended claims.

What is claimed is:

1. Welded Steel tube of high tensile strength, said tube being made of a steel alloy consisting essentially of between about 0.1% and less than 0.23% carbon, between about 0.20% and less than 0.50% silicon, about 1.00 to 1.35% manganese, less than 0.040% phosphorus, less than 0.040% sulfur,

between about 0.10% and less than 0.30% copper, between about 0.10% and less than 0.50% chromium, about 0.0l0-0.080 aluminum, and the balance substantially of iron.

2. Tube according to claim 1 wherein said' tube is a welded tube.

3. Tube according to claim 1 wherein said steel alloy is a killed steel.

4. Tube according to claim 3 wherein said alloy is an aluminum killed steel.

5. Tube according to claim 1 wherein the amount of manganese is about 1.00 to 1.35%.

6. Tube according to claim 1 wherein said alloy contains 0.15-0.20% carbon, 0.20-0.50% silicon, l.0-l.35% manganese, 0. l00.20% copper, and 0. l00.40% chromium.

Claims

2. Tube according to claim 1 wherein said tube is a welded tube.
3. Tube according to claim 1 wherein said steel alloy is a killed steel.
4. Tube according to claim 3 wherein said alloy is an aluminum killed steel.
5. Tube according to claim 1 wherein the amount of manganese is about 1.00 to 1.35%.
6. Tube according to claim 1 wherein said alloy contains 0.15-0.20% carbon, 0.20-0.50% silicon, 1.0-1.35% manganese, 0.10-0.20% copper, and 0.10-0.40% chromium.