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Method for manufacture of steel products of precipitation hardened martensitic steel, steel products obtained with such method and use of said steel products

A technology of martensite and martensite transformation, applied in the direction of manufacturing tools, heat treatment equipment, furnace types, etc., can solve problems such as inability to act

Inactive Publication Date: 2004-03-03
KONINK PHILIPS ELECTRONICS NV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Applicant expressly reserves the right to show that such structures and / or methods do not constitute prior art with respect to the present invention

Method used

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  • Method for manufacture of steel products of precipitation hardened martensitic steel, steel products obtained with such method and use of said steel products

Examples

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Embodiment 1

[0018] A steel material suitable for use in the invention having the composition described above was produced in strip form from a scaled seven ton melt in a high frequency furnace and then subjected to rolling. The solidification process after melting 1 is shown in figure 1 , where the temperature versus time curve is represented by the solid line. Solidification of the melt leads to crystallization of Ti(C,N), thereby binding free carbon and free nitrogen. Binding of free nitrogen is important because otherwise free nitrogen would inhibit the isothermal martensitic transformation.

[0019] In order to give the material an austenitic structure and sufficient ductility for hot rolling, the steel is reheated to a temperature of 1150°C-1250°C and soaked at this temperature for at least 1 hour before rolling. Reheating to a temperature 2 of 1150°C-1250°C is followed by hot rolling 3 . Hot rolling 3 produces a strip-shaped material with suitable grain size and uniform distribut...

Embodiment 2

[0035]A steel material or product having the same chemical composition as in Example 1 can be made into a diaphragm leaf spring functioning as a return spring in a fluid valve. Depending on the desired accuracy of the dimensions of the diaphragm leaf spring, it is possible to have so-called confined austenite in the product after quenching 9 . The solution treatment 7 is preferably followed by a sensitive heat 8, which causes the destabilization of the austenite so as to promote the subsequent isothermal martensitic transformation. Diaphragm leaf springs for many applications use complex shapes which require strong deformations during forming. This deformation causes strain-induced martensite, which must be transformed into austenite by solution treatment7. The method of the present invention is extremely suitable for preparing the steel stock used in this application.

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Abstract

A method for the manufacture of steel products and products thus produced, wherein steel is subjected to precipitation hardening in a martensitic structure subsequent to soft annealing and thereafter shaping. The method steps include shaping followed by solution annealing between 1200 DEG C and 1050 DEG C, quenching from the solution annealing temperature with a quenching speed of at least 5 DEG C per second to a temperature below 500 DEG C, subjecting said steel to an isothermal martensitic transformation and subsequently hardening the steel at a temperature between 450 DEG C and 550 DEG C to precipitate particles out from solution into said martensitic structure.

Description

field of invention [0001] The present invention relates to a method of producing a steel product, wherein the steel, after soft annealing, undergoes isothermal martensite formation and precipitation hardening in the martensite structure and is shaped. The invention also relates to the steel product produced by this method and the use of such a steel product. Background of the invention [0002] In the following discussion of the prior art, reference is made to certain structures and / or methods. However, the following references should not necessarily be taken as an admission that such structures and / or methods constitute prior art. Applicant expressly reserves the right to show that such structures and / or methods do not constitute prior art with respect to the present invention. [0003] In the published international patent application WO 93 / 07303, a production method of the above type has been described, in which the transformation to the martensitic structure is accompl...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D6/00C21D6/02C21D6/04C21D9/02C21D9/18C22C38/00C22C38/52
CPCC21D2211/008C21D6/02C21D6/04C21D6/004C21D1/26C21D1/18C21D6/002C21D9/02C21D9/18
Inventor 扬-奥罗夫·尼尔松瑟伦·奥尔松胡贝特·舒尔德·布洛乌阿德里安·范德格里杰恩
Owner KONINK PHILIPS ELECTRONICS NV