SE500146C2 - Use of a steel for pipes for reinforcing car doors - Google Patents

Abstract

According to the invention there is proposed for the production of pipes for the reinforcement of the doors of motor vehicles, the use of a steel alloy comprising at most 0.35% of carbon, at most 0.50% of silicon, at most 1.80% of manganese, at most 0.030% of phosphorus, at most 0.030% of sulphur, from 1.8 to 2.2% of chromium, from 0.4% to 0.7% of molybdenum, at most 1.5% of nickel, preferably from 0.5 to 1%, and from 0.025 to 0.050% of aluminium, and iron as the remainder, with the pipes being produced by the hot rolling process. The proposed steel alloy offers the advantage that, in comparison with comparable steel alloys, considerably improved mechanical properties are achieved, without the disadvantages of additional heat treatments being required to achieve these advantages.

Description

2 pipes which, even with relatively small round cross-sections, meet the requirements specified above and make it unnecessary to subject the manufactured pipes to a costly heat treatment. This object is fulfilled with the invention stated in claim 1.

In particular, the alloy components nickel and aluminum in the specified contents entail a limitation of the required carbon content and a finer-grained structure, which is why pipes made of this steel alloy by hot rolling meet the set requirements even when using relatively small pipe dimensions while maintaining it from a manufacturing point of view. particularly desirable round cross-sectional shape.

Compared to what is the case with the use of boron-containing alloys, the essential advantage is obtained that all additional heat treatment can be dispensed with, thanks to the fact that the significant improvement of the mechanical properties arises through the hot rolling process itself used to make the pipes.

It has thus been possible to determine that pipes made from the steel alloy used in the invention by hot rolling have a tensile strength Rm of about 1400 to 1900 N / mm 2 and a yield strength Re of at least 1100 N / mm 2, ie significantly better mechanical properties than obtained from pipes of the steel alloy specified in DE-C-2 750 867. Regarding the addition of Ni, a content of 0.596 increases the toughness by about 25%, while a content of 1.5% increases the toughness by about 40%. The nickel content should therefore be between these values, preferably in the range 0.5 to 1.096.

In the same way, the position alloy used in the invention also gives at least as good values for the other parameters that are of interest as the steel alloy according to DE-C-2 750 867.

Preferably, the tubes should be manufactured at a final rolling temperature of at least 7500 C, but most preferably at a final rolling temperature in the range 980 to 10800 C. These final rolling temperatures ensure optimal structural properties of the produced tubes.

Claims (2)

gl "UH. -L 3 _. * ~ FÅ" i f. f 4 .f Patent claim: "VVM" 'LW / i Use of a steel, consisting of a maximum of 0.35% C maximum 0.50% Si maximum 1.80% Mn maximum 0.030% P maximum 0.030% S maximum 1.596 Ni 1.8 to 2.2% Cr 0, 4 to 0.7% Mo 0.025 to 0.050% Al, the remainder Fe as material for the production of pipes, which in hot-rolled condition are used for reinforcement of car doors, the final rolling temperature of the pipes being within intervals 980 min 1oso ° c. Use of a steel for the purpose specified in claim 1 and with the composition specified in claim 1, but with not less than 0.596 and not more than 1,096 Ni.