Method for eliminating defective structure in structural alloy steel and tool steel substrate by using impulse current

Abstract

A method for eliminating defective structures in basal bodies of structural alloy steel and tool steel by applying pulse current is disclosed, steel products are placed in a heat treatment electric furnace, positive and negative two end surfaces of the steel products are connected with a pulse current generator out of the furnace through lead; when the structural alloy steel is heated to the critical phase-transition temperature A+50 DEG C or the tool steel is heated to the critical phase-transition temperature A+(20-50 DEG C), the heat preservation is begun, at the same time, the pulse current generator is started up to input the pulse current whose intensity is 850A-1000A, frequency is 50Hzto30Hz, after maintaining for 10-15 minutes, the structural alloy steel is carried out according to normalizing procedure and cooled out of the furnace, the tool steel is cooled within the furnace; the method inputs the low frequency pulse large current with quite small duty ratio at the same time of heating the metal to meet the demand of phase-transition thermodynamics, thus improving the change speed of the structures, thinning grains in a very short time, clearing the banded structures, netlike structures in the steel and providing ideal basal body structure for the subsequent heat treatment procedure.

Description

technical field [0001] The invention relates to a method for quickly and effectively eliminating defect structures in alloy structural steel and tool steel substrates by applying pulse current. Background technique [0002] 1. Low and medium carbon steel alloy structural steel such as: 20, 45, G20CrNi 2 MoA, 12Cr 2 Ni 4 A, 20CrMnTi, 20CrNi and other materials, when rolling and forging, along the rolling direction, there will often be two kinds of organizations, ferrite and pearlite, which are alternately distributed in layers. This organization seen under a microscope is called bands, such as figure 1 shown. [0003] The reason for the formation of banded structures in low and medium carbon steels and alloy structural steels is due to slow cooling from the austenitic state and passing through the material's transformation critical temperature Ar 3 and Ar 1 In the temperature range or hot pressure processing in this temperature range, the various elongated non-metallic ...

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Problems solved by technology

[0010] In order to solve the problem that the band structure in the alloy structural steel and the network structure in the alloy tool steel and carbon tool steel cannot be effectively removed in the traditional heat treatment process, the present invention proposes a method of rapidly and effectively eliminating the The method of defect structure in the steel matrix. In this method, when the metal is heated to meet the thermodynamic conditions of phase transformation, a low-frequency pulse with a small duty cycle and a large current is input to obtain additional activation energy ΔE and increase diffusion during the transformation of the matrix structure. Coefficient D, in order to change the kinetic conditions of the phase transformation of the material, increase the structure transformation speed, refine the grain in a short time, remove the band structure and network structure in the steel, and provide an ideal matrix structure for the subsequent heat treatment process

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