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A non-brittle nitriding process for construction machinery pistons

A technology for construction machinery and pistons, applied in metal material coating technology, solid-state diffusion coating, coating, etc., can solve problems such as high surface brittleness, easy cracking and failure

Active Publication Date: 2019-01-01
JIANGSU FENGDONG HEAT TREATMENT & SURFACE MODIFICATION ENG & TECH RES CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Construction machinery pistons need to bear a large load during use, so construction machinery pistons have high requirements for wear resistance on their surfaces. The wear resistance of construction machinery pistons made of 42CrMo quenched and tempered by conventional nitriding processes can reach Requirements, but its surface is brittle and easy to crack and fail

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] a. Put the engineering machinery piston into the furnace tank, vacuumize the furnace tank for 15 minutes until the vacuum degree in the furnace tank is 0.2mbar, and then fill the furnace tank with nitrogen with a purity of 99.9995%, and the nitrogen filling time is 5 minutes. To the vacuum degree in the retort is 1050mbar.

[0030] b. Heat the engineering machinery in the furnace tank for 120 minutes to a temperature of 520°C.

[0031] c. Nitriding: Introduce ammonia gas into the retort, control the nitrogen potential Kn=4.3 through the hydrogen probe, adjust the ammonia decomposition rate to 37%, keep warm for 360min, continue to introduce ammonia gas into the retort, and control the nitrogen through the hydrogen probe Potential Kn = 0.8, corresponding to adjust the decomposition rate of ammonia to 70%, keep warm for 1020min.

[0032] d. After nitriding is completed, vacuumize the furnace tank for 5 minutes until the vacuum degree in the furnace tank is 0.2mbar, and t...

Embodiment 2

[0036] a. Put the construction machinery piston into the furnace tank, vacuumize the furnace tank for 20 minutes until the vacuum degree in the furnace tank is 0.2mbar, and then fill the furnace tank with nitrogen with a purity of 99.9995%, and the nitrogen filling time is 10 minutes. To the vacuum degree in the retort is 1050mbar.

[0037] b. Heat the engineering machinery in the furnace tank for 130 minutes to a temperature of 525°C.

[0038] c. Nitriding: Introduce ammonia gas into the retort, control the nitrogen potential Kn=4.0 through the hydrogen probe, adjust the ammonia decomposition rate to 39%, keep warm for 370min, continue to introduce ammonia gas into the retort, and control the nitrogen through the hydrogen probe Potential Kn = 0.7, corresponding to adjust the ammonia decomposition rate of 72%, keep warm for 1040min.

[0039] d. After nitriding is completed, vacuumize the furnace tank for 10 minutes until the vacuum degree in the furnace tank is 0.2mbar, and t...

Embodiment 3

[0043] a. Put the engineering machinery piston into the furnace tank, vacuumize the furnace tank for 18 minutes until the vacuum degree in the furnace tank is 0.2mbar, and then fill the furnace tank with nitrogen with a purity of 99.9995%, and the nitrogen filling time is 8 minutes. To the vacuum degree in the retort is 1050mbar.

[0044] b. Heat the engineering machinery piston in the retort for 125 minutes to a temperature of 530°C.

[0045] c. Nitriding: Introduce ammonia gas into the retort, control the nitrogen potential Kn=4.6 through the hydrogen probe, adjust the ammonia decomposition rate to 35%, keep warm for 350min, continue to introduce ammonia gas into the retort, and control the nitrogen through the hydrogen probe Potential Kn = 0.9, corresponding to adjust the ammonia decomposition rate %, keep warm for 1000min.

[0046] d. After nitriding is completed, vacuumize the furnace tank for 8 minutes until the vacuum degree in the furnace tank is 0.2mbar, and then fil...

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Abstract

The invention discloses a non-brittle nitriding process for a piston of engineering machinery. The process comprises the following steps: a, putting the piston of engineering machinery in a furnace pot, vacuumizing the furnace pot, and then filling nitrogen into the furnace pot; b, heating the piston of engineering machinery in the furnace pot to 520-530 DEG C; c, nitriding: introducing ammonia gas into the furnace pot, controlling the nitrogen potential Kn equal to 4.0-4.6 through a hydrogen probe, correspondingly adjusting the decomposition rate of ammonia gas to 35-39%, performing insulation for 350-370 minutes, continuously introducing ammonia gas into the furnace pot, controlling the nitrogen potential Kn equal to 0.7-0.9 through the hydrogen probe, correspondingly adjusting the decomposition rate of ammonia gas to 70-74%, and performing insulation for 1000-1040 minutes; d, vacuumizing the furnace pot, and then filling nitrogen into the furnace pot; and e, performing furnace cooling on the piston of engineering machinery to 40-60 DEG C, discharging the piston out of the furnace pot, and naturally cooling the piston to room temperature. According to the process disclosed by the invention, by accurately controlling the nitrogen potential through the hydrogen probe and adjusting the decomposition rate of ammonia gas of a corresponding ammonia gas decomposition instrument, the nitriding effect is ensured, and the using requirements on a product are satisfied.

Description

technical field [0001] The invention belongs to metal surface heat treatment processing, and more specifically relates to a non-brittle nitriding process for engineering machinery pistons. Background technique [0002] Nitriding has proven to be widely used as a heat treatment process to improve the wear resistance of the surface of parts. GB / T11354-2005 "Determination of Depth of Nitriding Layer and Inspection of Metallographic Structure of Iron and Steel Parts" stipulates the determination and evaluation of the depth brittleness, looseness and vein-like nitrides of the nitriding layer on the surface of iron and steel parts, and the Vickers hardness tester is used for surface brittleness Load with a load of 10Kgf, and observe the integrity of the indentation with a 100 times magnifying glass after unloading. In actual application, it is found that this method cannot fully reflect the brittleness requirements of engineering machinery pistons. The user requires a Rockwell ha...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C8/26
CPCC23C8/26
Inventor 史有森朱雪明王琴
Owner JIANGSU FENGDONG HEAT TREATMENT & SURFACE MODIFICATION ENG & TECH RES CO LTD