Technology of heat treatment of high strenth fastener promotes
From;    Author:Stand originally
Heat treatment technology is right high strenth fastener especially its immanent quality is having crucial effect, accordingly, want to produce a high grade high strenth fastener, must want to have advanced heat treatment technology and equipment.

Current situation of heat treatment of fastener of high strenth of car of 1 east wind

Fastener of high strenth of east wind car has 4 function order and degree, namely 8.8, 9.8, 10.9, 12.9 class. And the high strenth fastener of these 4 grade should undertake moving pledging handling.

Heat treatment attune is to improve the integrated and mechanical performance of fastener character, compare in order to satisfy the tensile strength value that the product provides and Qu Jiang. Accordingly, tone pledges craft is opposite raw material, control of furnace temperature control, the atmosphere inside furnace, quench quality of medium, heat treatment detects wait to have firm demand with control.

1.1 material

Material of fastener of high strenth of east wind car basically has steel of ML35, 35K, ML40Cr, ML35CrMo to wait, among them 75%ML35CrMo steel import. Material basically has pane to slant the problem such as analyse, decarbonization, crackle. Material needs to undertake the ball changes anneal before cold figuration, anneal undertakes inside oily furnace, protective atmosphere is not had inside furnace, put in decarbonization phenomenon.

1.2 heat treatment move qualitative furnace

The high strenth fastener that 12.9 class give priority to undertakes moving pledging handling on product line of casting catenary furnace. The temperature inside furnace, atmosphere is controlled by the computer, use Rx gas to regard protection as atmosphere, heat to be able to accomplish effective control with antirust decarbonization, fastener is heating the quality in the process is in good condition.

The high strenth fastener that 8.8 class give priority to is undertake moving pledging handling on shake bottom furnace, suffer the effect of structure of shake bottom furnace, atmosphere of can poor, Rx controls furnace sealing not easily, big, spare parts is in furnace temperature difference in temperature existence collision and time length heat inside furnace not, send, fastener is heating the quality in the process decarbonization of poorer, existence, touch, heat inhomogenous wait for a phenomenon.

1.3 quench medium

Fastener of high strenth of east wind car is moved qualitative, quench medium has two kinds, ML35 kind quench with buck, carbolic alloy steel uses common and mechanical oil hardening in. Quench in buck existence quenchs craze phenomenon. Quench in common and mechanical oil existence hardness not all unqualified even phenomenon, must undertake iteration moving pledging handling in production.

1.4 detect

After heat treatment of fastener of high strenth of east wind car detect, basically detect hardness, tensile strength, metallographic is organized (qualitative detect) , of Rx gas analysis, 12.9 class have 100 % magnetic particle crackle of examination of nondestructive of jade-like stone light. And the quantitative analysis that quenchs cooling performance measurement, metallographic organizes medium, spare parts is immanent blemish and hardness are grading still do not have detect method.
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