Use of a steel alloy for making tubes to produce compressed gas containers or for making formed structures in light weight steel construction

Abstract

A method of using a steel alloy, the steel alloy having a composition containing in mass %, 0.09-0.13% C, 0.10-0.50% Si, 1.10-1.80% Mn, max. 0.02% P, max. 0.02% S, 1.00-2.00% Cr, 0.20-0.60% Mo, 0.02-0.06 Al, 0.10-0.25% V, the balance iron and incidental impurities, includes the steps of forming a tube from the steel alloy; air hardening the tube in the presence of inert gas, and incorporating the tube in the production of a compressed gas container. The steel composition may also be used as material for producing formed structures in light weight steel construction.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application is a continuation of prior filed copending PCT International application no. PCT / DE03 / 00394, filed Feb. 11, 2003, which designated the United States and on which priority is claimed under 35 U.S.C. §120, the disclosure of which is hereby incorporated by reference, and which claims the priority of German Patent Applications, Serial No. 102 06 612.4, filed Feb. 15, 2002, 102 21 487.5, filed May 15, 2002, and 102 21 486.7, filed May 15, 2002, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] The present invention relates to use of a steel alloy for making tubes to produce compressed gas containers or for making formed structures in light weight steel construction. [0003] Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. [0004] Compressed gas containers are typically made of annealed car...

AI Technical Summary

Benefits of technology

The present invention relates to a steel alloy for making compressed gas containers and light weight steel constructions. The steel alloy has a specific composition that includes 0.09-0.13% C, 0.10-0.50% Si, 1.10-1.80% Mn, max. 0.02% P, max. 0.02% S, 1.00-2.00% Cr, 0.20-0.60% Mo, 0.02-0.06% Al, 0.10-0.25% V, and balance iron and incidental impurities. The steel alloy has high strength and notched impact toughness, and is cost-effective compared to other steel compositions. The method of using the steel alloy involves air hardening the tube by heat treatment, and incorporating the formed structure into light weight steel construction. The formed structure can also be subjected to high temperature galvanizing for further protection against corrosion. The use of the steel alloy results in a higher base strength and reliable strength of the welded joints.

Problems solved by technology

Thus, scale must be removed by a complicated sand blasting process.

Another drawback is the application of oil cooling which entails health hazards.

Another drawback involves the high content of carbon which renders the steel alloy unsuitable when, for economical reasons, quick welding processes such as active-gas metal-arc welding with mixed gas (MAG) or laser beam welding, are demanded for making pressure containers, because of the risk of cracks.

This type of steel can be tempered only with water and only in the tool so that the overall production is cumbersome.

Without tempering, this steel would lack a required strength, while tempering results in scaling that can be eliminated only by a comparably long pickling process which in turn leads to hydrogen embrittlement.

Another drawback of this type of steel is a substantial loss in strength in heat impact zones that have been formed by welding seams, when tempered formed structures are joined together by welding.

Although it may be conceivable to completely temper a formed structure that is composed of several single components, the finished formed structure is, however, warped or distorted.

Loss in strength of such steel is also experienced during high temperature galvanizing, such as hot galvanizing.

Increase in strength can be realized by higher transformation strain which, however, is undesired for many formed structures used in the automobile industry.

This type of steel also experiences significant structural changes during high temperature galvanizing.

Although the strength could conceivably be increased by higher transformation strain, this course of action is, as stated above, undesired for many formed structures used in the automobile industry.

Special steel having a tensile strength Rm of 800 N / mm2, yield point Rp0.2 of 370 N / mm2, and stretch A5 of 53% results in high material costs while exhibiting an insufficient base strength.

In addition, the strength of special steel can also only be increased by higher transformation strain which cannot always be attained in components of the automobile industry.