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A new spheroidizing annealing method for low carbon bainite steel

A carbon bainitic steel and spheroidizing annealing technology, which is applied to the spheroidizing annealing process of low carbon bainitic steel, can solve the problems of poor spheroidizing effect, unstable quality, difficult control, etc., achieve stable quality, improve Spheroidizing effect, the effect of overcoming the difficulty of controlling the annealing process

Active Publication Date: 2018-12-21
JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] From the actual production results, when the traditional spheroidizing annealing method is used to perform spheroidizing annealing on low-carbon bainite steel, it is difficult to control, the quality is unstable after annealing, and the spheroidizing effect is poor.

Method used

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  • A new spheroidizing annealing method for low carbon bainite steel
  • A new spheroidizing annealing method for low carbon bainite steel
  • A new spheroidizing annealing method for low carbon bainite steel

Examples

Experimental program
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Effect test

Embodiment 1

[0025] Example 1: The composition of steel type 1 is: C: 0.18%, Si: 0.12%, Mn: 0.76%, P: 0.013%, S: 0.032%, Cr: 0.82%, Ni: 1.59%, Cu: 0.01%, Mo: 0.30%, Al: 0.032%, the balance is Fe and unavoidable impurity elements. According to the method of the invention, steel type 1 is first heated to 350°C-500°C for 3-6 hours, then heated to 670°C-750°C for 10-20 hours, and then air-cooled. The obtained annealed spherical pearlite content is about 96% (eg Image 6 shown).

Embodiment 2

[0026] Example 2: The composition of steel type 2 is: C: 0.17%, Si: 0.08%, Mn: 0.81%, P: 0.018%, S: 0.027%, Cr: 0.87%, Ni: 1.61%, Cu: 0.01%, Mo: 0.35%, Al: 0.029%, the balance is Fe and unavoidable impurity elements. According to the method of the invention, steel type 2 is first heated to 590°C-660°C for 4-8 hours, then heated to 680°C-750°C for 10-20 hours, and then air-cooled. The obtained annealed spherical pearlite content is about 93% (eg Figure 7 shown).

Embodiment 3

[0027] Example 3: The composition of steel type 3 is: C: 0.23%, Si: 0.23%, Mn: 1.26%, P: 0.015%, S: 0.003%, Cr: 0.52%, Ni: 0.98%, Cu: 0.10%, Mo: 0.55%, Al: 0.031%, the balance is Fe and unavoidable impurity elements. According to the method of the invention, steel type 3 is first heated to 380°C-520°C and kept for 3-6 hours, then heated to 670°C-750°C, kept for 12-20 hours, and then air-cooled to obtain an annealed structure with spherical pearlite content is 100% (eg Figure 8 shown).

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Abstract

The invention relates to a novel spheroidizing annealing method for low-carbon bainite steel. Firstly, the steel is heated to a low temperature T3 for heat preservation, and thus retained austenite in the steel is fully converted into ferrite and carbide. Then the steel is heated again to a high temperature T4 for heat preservation, and thus carbide particles are separated out and grow up into a globular shape. Finally a globular carbide+ferrite spheroidized structure is obtained and then air-cooled or slow-cooled to the room temperature. According to the above temperatures, T3 is 350 DEG C-550 DEG C or 570 DEG C-660 DEG C, and the heat preservation time of the low temperature segment is 3-8 hours; T4 is 670 DEG C-770 DEG C, the heat preservation time of the high temperature segment is 8-20 hours, the temperature increase speed between the T3 and the T4 is not limited, and the carbon content in the steel is smaller than or equal to 0.3 wt%. After annealing, the content of globular pearlites in the steel is larger than or equal to 90%. According to the annealing process, the structure quality after annealing can be stabilized, the spheroidizing effect is improved, and the defect of difficult control over the annealing process of low-carbon bainite steel in the prior art is overcome.

Description

technical field [0001] The invention relates to a spheroidizing annealing process of low-carbon bainite steel with a carbon content of ≤0.30%. Background technique [0002] Today, the manufacturing industry has higher and higher requirements for manufacturing precision, efficiency and material utilization, and the current environmental protection requirements are also increasing, which makes the application of cold forging technology more and more widely; therefore, steel for cold forging The use of will be a development trend in the future. Steel for cold forging must be spheroidized annealed before cold forging deformation to obtain good plasticity and appropriate hardness. [0003] Commonly used traditional spheroidizing annealing methods are as follows: [0004] Method 1, such as figure 1 As shown, long-term insulation at a temperature slightly lower than Ac1 makes the cementite sheets in the flaky pearlite gradually spheroidize. This method finds that the time for sp...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/32
CPCC21D1/32C21D2211/004C21D2211/005
Inventor 王新社谢文新阮小江黄镇窦胜涛张磊周佩荣刘学文孙鸿平卢明霞曾海霞
Owner JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD