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Preparation method of 7CrSiMnMoV diameter-expanding die sheet

A technology for die and alloy steel, which is applied in the field of preparation of expanding die, can solve the problems of high content of alloy elements, high price, loss, etc., and achieves the effects of excellent mechanical properties, reduced machining cost, and reduced raw material cost.

Active Publication Date: 2015-02-18
HUNAN UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

C12Mo1V1 and C12MoV are expensive due to the high content of alloy elements, and a large number of carbides in the alloy structure can easily lead to cracks and fracture of the die
In addition, since the length / thickness of the die reaches 25, the heat treatment deformation is very serious, which brings great difficulties to the subsequent mechanical processing. It is easy to cause cracks and breaks in the mold, seriously affecting the production efficiency of the steel pipe, and in severe cases, it will cause pipe jamming and bring great losses

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] The present embodiment is a large-scale 7CrSiMnMoV expanding die. Its preparation method is as follows:

[0017] 1) Forging the 7CrSiMnMoV alloy steel billet (non-metallic inclusions: A: 1; B: 1.5; C: 1; D: 0.5) refined by electroslag remelting, the initial forging temperature is 1150 ℃, and the final forging temperature is 860 ℃, three times of upsetting and drawing, the cumulative forging ratio is 7.2, after forging, the air is cooled to about 120 ℃, and the grain size of the alloy steel after forging is 8 grades. 2) 7CrSiMnMoV alloy steel forgings are put into the furnace and heated to 860°C, the heating rate is 30°C / min, kept for 4 hours, cooled to 700°C with the furnace, kept for 5 hours, cooled to 600°C with the furnace, and air-cooled. 3) Coat the surface of the machined 7CrSiMnMoV alloy steel expanding die with 2 mm of RLHY-31~33 high-temperature and anti-oxidation coating, and plug the holes with bolts. 4) 7CrSiMnMoV alloy steel expansion dies are suspended a...

Embodiment 2

[0020] The present embodiment is a medium-sized 7CrSiMnMoV expanding die. Its preparation method is as follows:

[0021] 1) Select the 7CrSiMnMoV alloy steel billet refined by electroslag remelting (non-metallic inclusions: A: 1.5; B: 1; C: 0.5; D: 0.5), for forging, the initial forging temperature is 1120 ℃, the final forging temperature is 830°C, three times of upsetting and drawing, the cumulative forging ratio is 8, air-cooled to about 80°C after forging, the grain size of the alloy steel after forging is 8.5. 2) 7CrSiMnMoV alloy steel forgings are put into the furnace and heated to 850°C with a heating rate of 35°C / min, held for 3 hours, cooled to 690°C with the furnace, held for 4 hours, cooled to 580°C with the furnace and air-cooled. 3) Coat the surface of the machined 7CrSiMnMoV alloy steel expanding die with 1.5mm RLHY-31~33 high-temperature and anti-oxidation coating, and plug the holes with bolts. 4) 7CrSiMnMoV alloy steel expansion dies are hung and placed in th...

Embodiment 3

[0024] This embodiment is a small 7CrSiMnMoV diameter expansion die. Its preparation method is as follows:

[0025]1) Select the 7CrSiMnMoV alloy steel billet refined by electroslag remelting (non-metallic inclusions: A: 1; B: 0.5; C: 1; D: 0.5), for forging, the initial forging temperature is 1100 ℃, and the final forging temperature is 800°C, three times of upsetting and drawing, the cumulative forging ratio is 9, air-cooled to about 60°C after forging, the grain size of the alloy steel after forging is 9 grades. 2) 7CrSiMnMoV alloy steel forgings are put into the furnace and heated to 840°C at a heating rate of 40°C / min, held for 2 hours, cooled to 680°C with the furnace, held for 3 hours, cooled to 550°C with the furnace and air-cooled. 3) Coat the surface of the machined 7CrSiMnMoV alloy steel expanded die sheet with RLHY-31~33 high temperature and anti-oxidation coating with a thickness of about 1mm, and plug the holes with bolts. 4) 7CrSiMnMoV alloy steel expansion di...

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PUM

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Abstract

The invention discloses a preparation method of a 7CrSiMnMoV diameter-expanding die sheet. The preparation method comprises the following steps: forging a 7CrSiMnMoV alloy steel billet subjected to electroslag remelting and refining; carrying out isothermal annealing on a 7CrSiMnMoV alloy steel forging; carrying out hole plugging on a 7CrSiMnMoV alloy steel diameter-expanding die sheet subjected to rough machining, and coating with a high-temperature-resistant anti-oxidation coating; putting the 7CrSiMnMoV alloy steel diameter-expanding die sheet into an atmosphere protection heating furnace; feeding nitrogen gas, ammonia gas and methanol, and heating; feeding nitrogen gas and methanol for protection, and austenitizing; quenching by using nitrate; and carrying out reshaped tempering. The 7CrSiMnMoV diameter-expanding die sheet prepared according to the invention does not have the defects such as quenching cracks, decarburization and the like, has excellent quenching depth, bending strength, compressive strength, impact toughness and hardness and the like, and can meet the needs of machining; and the 7CrSiMnMoV diameter-expanding die sheet is not deformed after being machined, therefore, the die sheet can meet the requirements of stably carrying out diameter expanding on 20000-30000 tubes.

Description

technical field [0001] The invention relates to a method for preparing a diameter-expanding die used in a mechanical diameter-expanding machine, in particular to a preparation method for a 7CrSiMnMoV diameter-expanding die with low cost, high hardness, high strength and high toughness. Background technique [0002] The expanding die-die sheet used in the mechanical expanding machine is the key die for forming steel pipes. During the expansion process, in order to cause the expansion deformation of the steel pipe, the expansion machine dies need to bear huge pressure and friction. In order to ensure the performance of the dies, imported cold work die steels C12Mo1V1 and C12Mo1V1 with high wear resistance and micro deformation are currently used. C12MoV preparation. C12Mo1V1 and C12MoV are expensive due to the high content of alloy elements, and a large number of carbides in the alloy structure can easily lead to cracks and fracture of the die. In addition, since the length / ...

Claims

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Application Information

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IPC IPC(8): C21D8/00C21D6/00C21D1/74C21D1/18B23P15/24
Inventor 王振生彭真杨双双宋力
Owner HUNAN UNIV OF SCI & TECH
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