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Spheroidizing annealing method for Cr and Mo steel with sheet type microstructure

A microstructure and spheroidizing annealing technology, which is applied in the field of metallurgy, can solve problems such as control technology that has not been reported in research, and achieve good application prospects, shortened holding time, and good cold heading performance

Inactive Publication Date: 2014-06-18
NORTHEASTERN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] To sum up, for Cr and Mo steel products, there is no public research report on the control technology of Cr and Mo steel spheroidizing annealing method aimed at the characteristics of lamellar structure

Method used

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  • Spheroidizing annealing method for Cr and Mo steel with sheet type microstructure
  • Spheroidizing annealing method for Cr and Mo steel with sheet type microstructure
  • Spheroidizing annealing method for Cr and Mo steel with sheet type microstructure

Examples

Experimental program
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Effect test

Embodiment 1

[0037] The Φ10mm wire rod for high-strength bolts is produced by using a 325mm×280mm bloom continuous casting-blanket-wire rolling process in a steel plant. The steel grades and compositions are shown in Table 1.

[0038] Table 1 Grades and compositions of steel grades

[0039] grade C Si mn P S Cr Mo SCM435 0.35 0.2 0.65 0.013 0.007 0.95 0.2

[0040] Place the rolled material sample with a height of 10mm and Φ13mm in a heating furnace, raise the temperature to 720°C and keep it for 5 hours, then cool it to 580°C, and then take the rolled material of Cr and Mo steel out of the furnace and air cool it to room temperature. The steel rolled material is wire-cut, then its cross-section is ground and polished, and it is corroded with 4% nitric acid alcohol and then observed under a metallographic microscope. The metallographic structure is as follows: Figure 5 As shown in (b), the SEM organization chart is as follows Figure 6 as shown in (b);...

Embodiment 2

[0044] The Φ13mm wire rod for high-strength bolts is produced by a 325mm×280mm bloom continuous casting-blanket-wire rolling process in a steel plant. The steel grades and compositions are shown in Table 1.

[0045] Place the rolled material sample with a height of 10mm and Φ13mm in a heating furnace, raise the temperature to 720°C and keep it for 4 hours, then cool it to 600°C, and then take the rolled material of Cr and Mo steel out of the furnace and air cool it to room temperature. The steel rolled material is wire-cut, then its cross-section is ground and polished, and it is corroded with 4% nitric acid alcohol and then observed under a metallographic microscope. The metallographic structure is as follows: Figure 7 As shown in (a), it can be seen from the figure that the spheroidal carbides are evenly distributed on the matrix, the spheroidized structure is rated as grade 5, and its microhardness is measured to be 175.35HV.

Embodiment 3

[0047] The Φ15mm wire rod for high-strength bolts is produced by using a 325mm×280mm bloom continuous casting-blanket-wire rolling process in a steel plant. The steel grades and compositions are shown in Table 1.

[0048] Place the rolled material sample with a height of 10mm and Φ15mm in a heating furnace, raise the temperature to 700°C and keep it for 4h, then cool it to 600°C, then take the rolled Cr and Mo steel out of the furnace and air cool to room temperature, and the Cr and Mo steels that have been spheroidized and annealed The steel rolled material is wire-cut, then its cross-section is ground and polished, and it is corroded with 4% nitric acid alcohol and then observed under a metallographic microscope. The metallographic structure is as follows: Figure 8 As shown in (a), the spheroidal carbides in the obtained annealed structure are more uniformly distributed on the matrix, the spheroidized structure is rated as grade 5, and its microhardness is measured to be 167...

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Abstract

The invention belongs to the technical field of metallurgy, and in particular relates to a spheroidizing annealing method for Cr and Mo steel with a sheet type microstructure. The spheroidizing annealing method comprises the steps of putting a Cr and Mo steel rolled product sample into a heating furnace, heating to 700-720 DEG C, preserving the temperature for 4-5 hours, then performing furnace cooling to 580-600 DEG C, taking out the Cr and Mo steel rolled product from the furnace, and cooling to room temperature, wherein the microhardness of the Cr and Mo steel rolled product subjected to spheroidizing annealing is 162.20-175.35HV, and the microstructure of the Cr and Mo steel rolled product consists of granular carbides dispersed on a ferritic matrix; the granular carbides have spheroidized structures in the level 5-6. According to the method, sub-medium temperature is preserved for certain time, and then the furnace cooling time is controlled, so that spheroidizing-annealed steel with high performance is obtained. The high preserved temperature is lower than the preserved temperature of the original technology, and the heat preservation time is shortened by almost three times, so that the energy consumption is obviously reduced, and the spheroidizing annealing efficiency is improved; the hardness of the steel subjected to the spheroidizing annealing technology is obviously reduced, the structure of a spheroidal pearlite is dispersive and fine, and the spheroidizing rate is high; the Cr and Mo steel subjected to spheroidizing annealing is high in cold heading performance and has a good application prospect.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, in particular to a spheroidizing annealing method for Cr and Mo steels with flake microstructures. Background technique [0002] Cr, Mo steel is a typical medium carbon alloy structural steel. The 12.9-grade high-strength and ultra-high-strength bolts for automobiles are basically Cr and Mo cold heading steel series. Domestic car engine steel has always relied on Japanese imports, which belong to high-grade cold heading steel with special requirements. The production process of high-strength bolts made of cold heading steel mainly includes several links such as wire rod, spheroidizing annealing, pickling, phosphating, saponification, drawing, and cold heading. Because cold heading forming has the advantages of high steel utilization rate, good mechanical properties, and suitable for automatic production, etc., most of the current high-strength bolt forming technologies use cold pier forming,...

Claims

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Application Information

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IPC IPC(8): C21D1/32C22C38/22
Inventor 祭程朱苗勇邱木生
Owner NORTHEASTERN UNIV
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