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Heat treatment method of high-strength bolt for electric tool

A technology of high-strength bolts and heat treatment methods, applied in heat treatment furnaces, heat treatment equipment, manufacturing tools, etc., can solve problems such as the inability to meet the requirements of high-power, lightweight electric tools

Active Publication Date: 2018-06-01
艾普零件制造(苏州)股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The traditional 12.9 grade bolts are made of 42CrMo steel. The commonly used heat treatment process is: first heating to 870°C for austenitization, then oil quenching at room temperature, and then tempering, and finally obtaining tempered martensite. Metallographic structure, its tensile strength is 1250MPa~1350MPa, which cannot meet the requirements of high-power and lightweight electric tools

Method used

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  • Heat treatment method of high-strength bolt for electric tool

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Comparison scheme
Effect test

Embodiment 1

[0047] A heat treatment method for high-strength bolts used in impact electric drills, using standard M10x35 / 12.9 bolts made of 42CrMo, therefore, the process before the bolt isothermal quenching heat treatment is omitted, mainly including the following steps:

[0048] (1) Send the bolt workpiece to the fully automatic salt quenching equipment under atmosphere protection and computer control, and the protection atmosphere is carbon monoxide;

[0049] (2) In the heating furnace of the fully automatic salt quenching equipment, the bolts are heated to 900°C and then held for 80 minutes for austenitization;

[0050] (3) Put the bolts that have been austenitized in step (2) into the salt tank of the salt bath furnace of the automatic salt quenching equipment, rapidly cool down to 370°C in the salt tank, and then keep it warm for 1.5 hours for austempering heat treatment; Wherein, the molten salt solution is a mixed solution of potassium nitrate with a mass ratio of 50% and sodium n...

Embodiment 2

[0056] A heat treatment method for high-strength bolts for electric hammers, using standard bolts of M10x35 / 12.9 grade, omitting forging and other general procedures, mainly including the following steps:

[0057] (1) Send the bolts to the fully automatic salt quenching equipment under atmosphere protection and computer control, and the protection atmosphere is carbon monoxide;

[0058] (2) In the heating furnace of the fully automatic salt quenching equipment, the bolts are heated to 820°C and then held for 40 minutes for austenitization;

[0059] (3) Put the bolts treated with austenite in step (2) into the salt tank of the salt bath furnace of the automatic salt quenching equipment, rapidly cool down to 330° C. in the salt tank, and then keep warm for 1 hour to carry out austempering heat treatment; , the molten salt solution is a mixed solution of potassium nitrate with a mass ratio of 50% and sodium nitrate with a mass ratio of 50%;

[0060] (4) Under normal temperature ...

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Abstract

The invention discloses a heat treatment method of a high-strength bolt for an electric tool. The heat treatment method comprises the following steps: bolt forging: a bolt blank is machined; and a heat treatment deformation is remained; bolt finish machining: a bolt semi-finished product is sent to full-automatic salt quenching equipment under atmospheric protection and computer control, is heatedto 820-920 DEG C for insulation by 35-80 minutes for austenizing, and is put in a salt tank of a salt bath furnace of the full-automatic salt quenching equipment to quickly cool to 300-400 DEG C forinsulation by 1-2 hours for isothermal quenching heat treatment; the bolt is washed by water under normal-temperature condition; an isothermal-quenched bolt is obtained after drying; and the surface of the bolt is blackened. After salt bath and isothermal quenching heat treatment of a traditional 12.9-grade bolt, the strength is improved to 14.9 grade, the tensile strength reaches 1500-1600 MPa, and the use working conditions of high-power electric tools are met; and meanwhile, the high-strength bolt after heat treatment achieves low deformation, improved wear resistance and prolonged servicelife.

Description

technical field [0001] The invention relates to a heat treatment method, in particular to a heat treatment method for high-strength bolts used in electric tools, and belongs to the field of metal material processing. Background technique [0002] High-strength bolts are the most widely used fasteners in the machinery industry. At present, 40Cr and 42CrMo are usually used to produce high-strength bolts in China, and their highest strength level is 1200MPa (grade 12.9). When traditional M10x35 / 12.9 bolts are applied to high-power electric tools such as electric drills, electric grinders, electric wrenches and electric screwdrivers, due to the high notch sensitivity of high-strength bolts, when the tensile strength exceeds 1200MPa, the phenomenon of delayed fracture is prominent , It is easy to cause delayed fracture and fatigue fracture at the gap concentration part such as the transition between the rod and the head or the root of the thread, resulting in early failure. [0...

Claims

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Application Information

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IPC IPC(8): C21D9/00C21D1/20C21D1/607C21D1/74
CPCC21D1/20C21D1/607C21D1/74C21D9/0093
Inventor 夏勇陈明志
Owner 艾普零件制造(苏州)股份有限公司
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