JP2010501733A - Steel for producing a mechanical member having higher strength and capable of breaking and separating, and processing method - Google Patents

Abstract

  In the present invention, the chemical composition has a mass percentage of the following contents: 0.40% ≦ C ≦ 0.60%, 0.20% ≦ Si ≦ 1.00%, 0.50% ≦ Mn ≦ 1.50% 0% ≦ Cr ≦ 1.00%, 0% ≦ Ni ≦ 0.50%, 0% ≦ Mo ≦ 0.20%, 0% ≦ Nb ≦ 0.050%, 0% ≦ V ≦ 0.30% , 0% ≦ Al ≦ 0.05%, 0.005% ≦ N ≦ 0.020% (in this case, the balance is composed of iron, impurities due to refining conditions, and residual substances) , A steel for a higher strength, separable mechanical member comprising at least two breakable separable members, and a processing method.

Description

  The present invention relates to a steel for manufacturing a mechanical member having higher strength and capable of breaking and separating, and a processing method. This material was developed, for example, to produce cracking connecting rods.

The steel must be suitable for forging or other hot forming. I'll be cooled while controlling the forging heat, 750 N / mm ² greater than the yield strength, tensile strength of 1000~1200N / mm ^2, elongation at break of greater than 10%, and having a cross-sectional shrinkage of greater than 25 percent, almost The pearlite structure must be adjusted. Of particular importance is its suitability for break separation.

  The desired properties are the production of raw materials by the chemical composition that can be adjusted accordingly by the appropriate adjustment of the pearlite structure by precipitation of special carbides (niobium carbide and vanadium carbide) and manganese sulfide. This can be achieved by adjusting the heat treatment after the forging performed or after the thermal deformation by appropriately controlling the temperature during thermal deformation in the forging as well as in the finish forging (thermomechanical treatment) of the member.

  So far for this purpose of use, for example, about 0.7% C, 0.5-0.9% Mn, 0.06% -0.07% S, and in some cases 0.1-0.1% 0.2% V (C70S6, 70MnVS4) nearly eutectoid steel, or about 0.4% C, about 1% Mn, 0.06-0.07% S, and about 0.0. An approximately eutectoid steel with an average carbon content of 3% V (36MnVS4) is used according to the technical customer manual.

  These steels have a pearlite structure with vanadium carbide and manganese sulfide, and satisfy the predetermined values in terms of mechanical properties. A disadvantage of the known material modification is that the conventional material modification consumes a large amount of raw materials for alloy materials which are expensive and tend to be insufficient. In particular, vanadium is now increasingly used in the field of precipitation-hardened ferritic-pearlite steel (AFP steel), which makes vanadium an increasingly prone material.

  The object of the present invention is to provide a novel material that has the required mechanical properties with respect to strength (and fatigue strength), and additionally integrates good tensile strength properties in tensile testing and at the same time good cracking properties. It is the avoidance of the aforementioned drawbacks by the proposal of steel. At the same time, it is desirable that the steel be well castable and forged. Furthermore, it is desirable that the new steel can be produced by replacing the vanadium content partially with niobium, with correspondingly adapted deformation methods and cooling methods, saving raw materials over known steels.

  High values for yield strength are obtained by precipitating niobium and vanadium carbides that form special carbides, dispersed as finely as possible, in addition to the basic chemical composition. This necessitates the dissolution of the existing carbides prior to the final heat deformation step, and a controlled temperature management during heat deformation and subsequent cooling. Finely dispersed precipitates can be obtained, inter alia, by immediately accelerating cooling at low final deformation temperatures. This in particular increases the yield strength and thus improves the yield strength ratio decisively.

  Tensile strength is determined by the basic composition of 0.5% C, 0.6% Si, 1.0% Mn, 0.23% Cr, 0.2% Ni, and 0.14% V. From the specified basic value, it can be adjusted to a desired range in the same manner by accelerating cooling immediately after thermal deformation.

  The intrinsic value of toughness is limited, inter alia, by appropriate addition of 0.06% to 0.07% sulfur and alloying. In this sense as well, the carbon content and the relatively high nitrogen content act positively.

  What is decisive for the good cracking property of the material is crystal fracture without macroscopic deformation. This is set by the alloy concept of high carbon content, high nitrogen content, and high sulfur content, and relatively little chromium content, relatively little nickel content, and relatively little molybdenum content. .

According to the solution, the present invention has the following chemical composition in weight percent:
0.4% ≦ C ≦ 0.6%; 0.2% ≦ Si ≦ 1.0%; 0.5% ≦ Mn ≦ 1.5%; 0% ≦ Cr ≦ 1.0%; 0% ≦ Ni ≦ 0.5%; 0% ≦ Mo ≦ 0.2%; 0% ≦ Nb ≦ 0.05%; 0% ≦ V ≦ 0.3%; 0% ≦ Al ≦ 0.05%; 0.005% ≦ N ≦ 0.020% (in this case, the balance consists of iron and impurities due to refining conditions)
The invention relates to a steel for producing a break-separable member for the automotive industry.

What are the disadvantages of the traditional variants?
-Partially expensive alloy flux (LZ) with 0.29% V (36MnVS4)
• What are the advantages of the new variant that is hardly a substitute for the patented steel material?
・ Lower alloy costs (only 0.14% V)
・ Customers do not depend on the only patented steel material

Claims (15)

A steel for a stronger, breakable separable mechanical member, characterized in that it comprises at least two breakable separable members, and a processing method, wherein the chemical composition of the steel is :
0.40% ≦ C ≦ 0.60%
0.20% ≦ Si ≦ 1.00%
0.50% ≦ Mn ≦ 1.50%
0% ≦ Cr ≦ 1.00%
0% ≦ Ni ≦ 0.50%
0% ≦ Mo ≦ 0.20%
0% ≦ Nb ≦ 0.050%
0% ≦ V ≦ 0.30%
0% ≦ Al ≦ 0.05%
0.005% ≦ N ≦ 0.020%
A steel for a mechanical member having a higher strength and capable of being separated by breakage, and a processing method, characterized in that the residue comprises iron and impurities and residual substances due to refining conditions. The steel has a chemical composition of the following 0.10% ≦ V ≦ 0.20%
The steel according to claim 1, characterized in that: The steel has a chemical composition of 0.020% ≦ Nb ≦ 0.030% as follows:
3. Steel according to claim 1 or 2, characterized in that The chemical composition of the steel is 0.010% ≦ N ≦ 0.020% as follows:
The steel according to any one of claims 1 to 3, characterized in that: The chemical composition of the steel is 0.45% ≦ C ≦ 0.55% as follows:
0.50% ≦ Si ≦ 0.70%
0.90% ≦ Mn ≦ 1.10%
0.10% ≦ Cr ≦ 0.40%
0.10% ≦ Ni ≦ 0.30%
0.10% ≦ V ≦ 0.20%
0.010% ≦ Al ≦ 0.020%
0.020% ≦ Nb ≦ 0.030%
0.010% ≦ N ≦ 0.020%
The steel according to any one of claims 1 to 4, characterized in that: The chemical composition of the steel is 0.45% ≦ C ≦ 0.55% as follows:
0.50% ≦ Si ≦ 0.70%
0.90% ≦ Mn ≦ 1.10%
0.10% ≦ Cr ≦ 0.40%
0.10% ≦ Ni ≦ 0.30%
0.10% ≦ V ≦ 0.20%
0.010% ≦ Al ≦ 0.020%
0.020% ≦ Nb ≦ 0.030%
0.010% ≦ N ≦ 0.020%
0.020% ≦ Ti ≦ 0.030%
The steel according to any one of claims 1 to 4, characterized in that: The chemical composition of the steel is 0.45% ≦ C ≦ 0.55% as follows:
0.50% ≦ Si ≦ 0.70%
0.90% ≦ Mn ≦ 1.10%
0.30% ≦ Cr ≦ 0.40%
0% ≦ Ni ≦ 0.20%
0.10% ≦ V ≦ 0.20%
0.010% ≦ Al ≦ 0.020%
0.020% ≦ Nb ≦ 0.030%
0.015% ≦ N ≦ 0.020%
The steel according to any one of claims 1 to 4, characterized in that:   8. A process according to any one of claims 1 to 7 for producing a break-separable member for an automobile structure having a substantially pearlite structure by precipitation of special carbides after forging and controlled cooling. Use of steel. The member according to claim 8, wherein the yield strength is more than 750 N / mm ² after cooling while controlling from the deformation temperature. The member according to claim 9, wherein the member has a tensile strength of more than 950 N / mm ^{2 and} less than 1200 N / mm ² after cooling while controlling from the deformation temperature.   The member according to claim 10, wherein the member has an elongation at break of more than 10% after being cooled while being controlled from the deformation temperature.   12. The member according to claim 11, wherein after cooling while controlling from the deformation temperature, the cross-sectional shrinkage ratio is more than 25%.   The member according to claim 12, wherein the member can be separated by breaking.   The member according to claim 13, which is suitable for induction heating and quenching.   15. The member according to claim 14, characterized in that the mechanical properties can be adjusted both in the forging raw material and in the member by thermomechanical treatment.