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Heat treating process for eliminating mixed crystal of low-alloy quick-cutting steel

A low-alloy, high-speed steel technology, applied in the field of heat treatment of low-alloy high-speed steel, can solve the problems of low secondary hardness and red hardness, small number of carbides, coarse grains, etc., and achieve tempered structure hardness and red hardness High, uniform grain, the effect of increasing the quenching temperature

Active Publication Date: 2009-04-29
江苏华久特钢工具有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Low-alloy high-speed steel itself has fewer primary carbides than general-purpose high-speed steel. Although the use of lower quenching temperature can avoid the generation of mixed crystals to a certain extent, it will lead to too few dissolved carbides, and the secondary structure obtained after tempering Minor hardness and red hardness are significantly lower
Increasing the quenching temperature can avoid the decrease in hardness, but it is easy to cause mixed and coarse grains

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] A low-alloy high-speed steel turning tool sample, the composition is: 1.02Wt%C, 1.5Wt%Si, 4.1Wt%W, 2.0Wt%Mo, 4.0Wt%Cr, 1.2Wt%V, 0.05Wt%RE, and the rest is Fe , the contents of impurities S and P are all lower than 0.02wt%. The parameters of the heat treatment process and process are as follows:

[0022] heat treater

art

art

Heating rate heating temperature

Spend insulation

time

cooling method

medium

annealing

300℃ / h

920℃

2h

>600℃30℃ / h

≤600℃ with furnace

cool down

Air

Air Quenching preheating 850℃ 10min salt bath Quenching 1180℃ 3min Stage Quenching salt bath three tempering 540℃ 1h×3 air cooling salt bath

[0023] The purpose of annealing is to eliminate the structural defects produced in the rolling process and obtain a better original balance structure. The purpose of quenching and preheati...

Embodiment 2

[0026] A low-alloy high-speed steel material, the composition is: 0.95wt% C, 1.97wt% Si, 3.8wt% W, 1.8wt% Mo, 4.0wt% Cr, 1.2wt% V, 0.05wt% RE, the rest is Fe, impurities The contents of S and P are respectively less than 0.02wt%.

[0027] The annealing process is the same as in Example 1, the quenching is carried out in an air furnace, the preheating temperature is 800°C, the time is 10min, the quenching heating temperature is 1180°C, and the test comparison is carried out according to three different holding times, the holding times are respectively 2min, 4min and 6min. Under various holding times, the quenched grain structure is good, and no abnormal growth of austenite is found. In the case of heat preservation for 2min, 4min, and 6min, the grain sizes were 12, 10, and 8, respectively.

Embodiment 3

[0029] A certain low-alloy high-speed steel material has the same composition as in Example 1.

[0030] After annealing at 890°C for 2 hours, the cooling method is the same as in Example 1. Quenching is carried out in an air furnace, the preheating temperature is 800°C, the time is 10min, the quenching heating temperature is 1180°C, and the holding time is 2min, 4min, and 6min respectively. Under the quenching and holding time of 2min and 4min, no mixed crystals appeared, and the grain sizes were 11 and 9.5 respectively. Under the quenching and holding time of 6min, the grain size increased uniformly to grade 8 without abnormal growth. The material quenched and held for 4 minutes was tempered, the tempering method was the same as in Example 1, and the hardness was HRC66.5. The average impact toughness is 28J / cm 2 , 600℃, 625℃ and 650℃ red hardness reach HRC64, HRC62.5 and HRC60.5 respectively.

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Abstract

The invention discloses a low alloy high speed steel mischcrystal elimination heat treatment process. The process comprises an annealing procedure and a quenching procedure. The annealing procedure comprises the following steps: heating up a low alloy high speed steel ingot to 890 to 910 DEG C at the speed of 300 DEG C per hour; controlling an annealing cooling rate at 25 to 30 DEG C per hour when the temperature of the ingot is above 600 DEG C; and cooling the ingot in the furnace when the temperature of the ingot is less than or equal to 600 DEG C. The quenching procedure comprises the following steps: preheating the annealed steel ingot to 800 to 850 DEG C, and controlling the heating time to be 5 to 15 minutes; continuing to heat up the ingot and increase the temperature to 1,170 to 1,190 DEG C, and controlling the holding time to be 2 to 6 minutes; and cooling the ingot through interrupted quenching. The process improves the annealing temperature rising rate and the annealing heating temperature, thereby enabling an annealed structure to be closer to an equilibrium structure, effectively avoiding the uneven growth of quenching austenite grains in a subsequent temperature span easily producing mischcrystal, improving the quenching temperature of the low alloy high speed steel, and reaching the aim of improving the red hardness of the high speed steel while simultaneously obtaining high tenacity.

Description

technical field [0001] The invention relates to a heat treatment process of low-alloy high-speed steel. The heat-treatment process is implemented for eliminating the defects of mixed crystal structure generated in the heat-treatment process of low-alloy high-speed steel. Background technique [0002] Mixed grain is a kind of defect structure that often appears in the production of high-speed steel. In essence, it is due to the high-speed steel that has been rolled and deformed. There are a large number of fine carbides in the structure. When the quenching temperature is not high, the fine carbides have a good pinning effect on the grain boundary. When the quenching temperature rises, A large amount of fine carbides dissolve, which weakens or loses the pinning effect on the grain boundaries, resulting in mixed crystals until the grains become coarser. There are two theories about the mechanism of mixed crystals, one is that it is the product of austenite recrystallization, a...

Claims

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Application Information

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IPC IPC(8): C21D6/00C21D1/26C21D1/18C22C38/34C22C38/24
Inventor 王九平芮志文陈锋
Owner 江苏华久特钢工具有限公司
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