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Short-process thermal treatment method of large 35CrNi3MoV steel forgings

A heat treatment method and technology for large forgings, applied in short-process heat treatment after forging of large forgings of 35CrNi3MoV steel, heat treatment field of 35CrNi3MoV steel, can solve the problems affecting the crystal phase structure of finished products, unreasonable process, complex process, etc., to improve production Efficiency, improved mechanical properties, and short process flow

Active Publication Date: 2013-10-09
JIANGYIN HENGYE FORGING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The purpose of the present invention is to solve the problems that the current heat treatment of large forgings of 35CrNi3MoV steel has complicated technology, high cost, and unreasonable technology that affects the crystal phase structure of the finished product. ) and tempering process of 35CrNi3MoV steel large-scale forging short-process heat treatment method, the method through slow cooling after forging, post-forging isothermal annealing process to inhibit the formation of large-scale forging flaky retained austenite to cut and eliminate tissue inheritance, through Quenching to uniformly refine the grains, and high temperature tempering to obtain good comprehensive mechanical properties

Method used

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  • Short-process thermal treatment method of large 35CrNi3MoV steel forgings

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Experimental program
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Effect test

Embodiment 1

[0030] Heat treatment of large 35CrNi3MoV steel forgings slowly cooled to room temperature after forging, the steps are as follows: first, heat the sample from room temperature to 650±10°C at a rate of 100±10°C / h for 8 to 10 hours (h), Then heat at a rate of 25±5°C / h from 650±10°C to 850±10°C for 12 hours to ensure uniform austenitization of the sample; then cool at a rate of 30±5°C / h to a nose tip temperature of 640°C± Incubate at 10°C for 66 hours to form a pearlite-based tissue, thereby eliminating tissue inheritance, and then cool to room temperature; then heat the sample to 650±10°C at a rate of 100±10°C / h for 3 to 5 hours, and then heat it at 25°C Heating at a rate of ±5°C / h to 860±10°C for 14 to 16 hours, and finally taking out the sample for oil quenching (quenching), the average grain size of the obtained prior austenite is above ASTM No.9 (such as figure 1 shown); Finally, the sample was heated from room temperature to 610±10°C at a rate of 100±10°C / h and kept for 20...

Embodiment 2

[0032] Heat treatment of large forgings of 35CrNi3MoV steel that was slowly cooled to room temperature after forging. The heat treatment steps of normalizing instead of quenching are as follows: first, heat the sample from room temperature to 650 °C at a rate of 300 °C / h for 9 h, and then Heating at a rate of 300°C / h from 650°C to 850°C for 12 hours to ensure uniform austenitization of the sample; then cooling at a rate of 30°C / h to 640°C±10°C for 48 hours to form pearlite-based Tissues, so as to eliminate tissue inheritance, and then cool to room temperature; then heat the sample to 650°C at a rate of 400°C / h for 4h, then heat at a rate of 300°C / h to 860°C for 15h, take out the sample and air cool (positive Fire), the average grain size of the obtained prior austenite is above ASTM No.8 (such as image 3 shown); Finally, the sample was heated from room temperature to 610 °C at a rate of 300 °C / h and kept for 12 h, and then the sample was taken out and air-cooled to room tempe...

Embodiment 3

[0034] The post-forging heat treatment of large forgings of 35CrNi3MoV steel that has been slowly cooled after forging is carried out. The heat treatment process steps of normalizing instead of quenching are as follows: first, the sample is heated from room temperature to 650 °C at a rate of 400 °C / h for 9 h, and then Heat at a rate of 300°C / h from 650°C to 850°C for 12 hours to ensure uniform austenitization of the sample; then cool at a rate of 30°C / h to 640°C±10°C and hold for 48 hours to form pearlite-based Then, the sample was heated to 650°C at a rate of 400°C / h for 4 hours, then heated to 860°C at a rate of 300°C / h for 15 hours, and finally the sample was taken out and air-cooled (Normalizing), the average grain size of the obtained prior austenite is above ASTM No.8 (such as Figure 5 shown); Finally, the sample was heated from room temperature to 610 °C at a rate of 400 °C / h for 12 hours, and then the sample was taken out and air-cooled to room temperature to obtain a...

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Abstract

The invention discloses a short-process thermal treatment method of large 35CrNi3MoV steel forgings. The short-process thermal treatment method of the large 35CrNi3MoV steel forgings comprises the steps of: slow cooling after forging, isothermal annealing, quenching (or normalizing) and tempering which are carried out sequentially, wherein the slow cooling after the forging is carried out by adopting a hole cooling or furnace cooling mode; in the isothermal annealing, the forgings are cooled to be at the nose temperature (640 DEG C) of a perlitic transformation zone after being austenitized at the velocity not higher than 30 DEG C / h as a furnace for isothermality for 48-66 hours, and pearlites are subjected to the isothermal decomposition and then are cooled to be at the room temperature; as the quenching is carried out, the recrystallization refining is achieve, and crystalline grains is equalized; finally, the tempering at high temperature can eb carried out to obtain a favorable comprehensive mechanical property. The short-process thermal treatment method of the large 35CrNi3MoV steel forgings, provided by the invention, is short in technology process (the total time lasts for about 120 hours), also can be used for obtaining the original austenite mean grain size above ASTMN0.8, can meet the manufacture requirement on power station equipment of thermal power, nuclear power and the like and also can meet the manufacture requirement on large force bearing and transmission structure components large metallurgy, mine and transportation equipment of our country.

Description

technical field [0001] The invention relates to a metal heat treatment method, in particular to a 35CrNi3MoV steel heat treatment method, in particular to a post-forging short-flow heat treatment method for large 35CrNi3MoV steel forgings. Background technique [0002] 35CrNi3MoV steel is a medium-carbon medium-alloy steel with high hardenability and good comprehensive mechanical properties. It is often used to manufacture large forgings with high strength and toughness. It is widely used in the manufacture of thermal power, nuclear power and other power station equipment and large-scale metallurgy, mining and transportation. Load-bearing and transmission structural components in equipment. [0003] The final forging temperature of large 35CrNi3MoV steel forgings is high, and air cooling is often used after forging. The non-equilibrium original structure such as tenite is re-austenitized under certain heating conditions, and the original coarse grains are inherited and rest...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D6/00C21D1/26C21D1/18C21D1/28
Inventor 胡华军卞良法卞晓春顾春卫许晓静陆文俊王宏宇宋振华陶俊王子路
Owner JIANGYIN HENGYE FORGING
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