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A spheroidizing annealing method for cr and mo steels with lamellar microstructure

A technology of microstructure and spheroidizing annealing, applied in the field of metallurgy, can solve problems such as no research reports in control technology, and achieve the effects of good application prospects, energy saving and high spheroidization rate.

Inactive Publication Date: 2016-06-29
NORTHEASTERN UNIV LIAONING
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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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  • A spheroidizing annealing method for cr and mo steels with lamellar microstructure
  • A spheroidizing annealing method for cr and mo steels with lamellar microstructure
  • A spheroidizing annealing method for cr and mo steels with lamellar microstructure

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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 Steel grade and composition

[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 Image 6 as shown in (b);

[0041] If adopted...

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 field of metallurgical technology, and particularly relates to a spheroidizing annealing method for Cr and Mo steel with flaky microstructure. Place the Cr and Mo steel rolled material samples in the heating furnace, raise the temperature to 700~720℃, keep the temperature for 4~5 hours, then cool the furnace to 580~600℃, then take the Cr and Mo steel rolled material out of the furnace and air-cool to room temperature, and pass through the ball The microhardness of chemically annealed Cr and Mo steel rolled products is 162.20~175.35HV, and its microstructure is granular carbides dispersed on the ferrite matrix. The granular carbides are spheroidized structures, rated 5~6. The method of the present invention obtains spheroidized annealed steel with good performance by maintaining the temperature at sub-temperature for a certain period of time and then controlling the furnace cooling time. The high-temperature insulation temperature used in the invention is lower than that of the original process, and the insulation time is shortened by nearly 3 times. Significantly save energy consumption and improve the efficiency of spheroidizing annealing; after the spheroidizing annealing process of the present invention, the hardness of the steel is significantly reduced, the spheroidized pearlite structure is more dispersed and fine, the spheroidizing rate is higher, and it has good cold heading performance and application prospects. .

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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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/32C22C38/22
Inventor 祭程朱苗勇邱木生
Owner NORTHEASTERN UNIV LIAONING
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