Method for producing a hot-formed and heat-treated steel component that is coated with a metal anti-corrosion coating from a sheet steel product

Abstract

The invention relates to a method for producing a steel component that is coated with a metal protective coating from a sheet steel product comprising at least 0.4 % by weight of Mn. In order to economically generate a high-strength steel component, while minimizing the risk of the development of metal-induced cracks, according to the invention the sheet steel product is annealed in a continuous furnace under an annealing atmosphere containing up to 25% by volume H2, 0.1 - 10% by volume NH3, H2O, the remainder being N2 as well as process-related inevitable impurities, at a dew point ranging between -50 DEG C and -5 DEG C and at a holding temperature of 400 - 1100 DEG C for a holding period of 5 - 600 s. The annealed sheet steel product has a nitride layer (N) 5 - 200 [mu]m thick, the particle size of which is finer than the particle size of the interior core layer (K) of the sheet steel product. After it has been coated with a metal protective layer, a blank is separated from the annealed sheet steel product and is soaked to an austenitizing temperature of 780 - 950 DEG C subsequent to an optional preforming step, is hot-formed to form the steel component and is cooled so quickly that a tempered martensitic structure forms in the sheet steel product.

Description

Technical field [0001] The invention relates to a method for manufacturing a hot-formed and quenched steel part coated with a metal anti-corrosion protective coating from a flat steel product, which has a manganese content of at least 0.4% by weight. Background technique [0002] In the 61st International Auto Show held in Frankfurt from September 15 to 25, 2005, it was reported in the article "The Potential of Lightweight Car Body" published in ThyssenKrupp Automotive AG's exhibition report. In practice, hot forming and quenching are especially used in the manufacture of high-strength body parts from boron alloy steel. A typical example of the boron alloy steel mentioned here is the steel labeled 22MnB5, which can be found in the Steel Handbook 2004 under the material number 1.5528. [0003] A steel similar to steel 22MnB5 is known in JP 2006104526 A. In addition to iron and unavoidable impurities, the known steel also contains (wt%) 0.05-0.55% C, maximum 2% Si, 0.1-3% Mn, maxim...

AI Technical Summary

Problems solved by technology

[0005] Hot forming of galvanized flat steel products into high-strength or highest-strength steel parts presents a particular difficulty

Steel sheets with metallic corrosion-resistant coatings must be heated to a temperature above the melting temperature of the metal of the protective coating due to hot forming and the subsequent or simultaneous quenching of the hot forming. Risk of so-called "liquefied metal embrittlement"

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