Method for 18 CrNiMo 7-6 carburization furnace front-sample annealing

A carburizing furnace and annealing technology, which is applied in the field of carburizing steel annealing, can solve the problems of increasing uncontrollable carburizing, low detection accuracy, and difficult observation of grain boundary carbides, etc., achieving short operation time, high detection accuracy, high efficiency effect

Inactive Publication Date: 2018-07-17
CHANGZHOU TIANSHAN HEAVY IND MACHINERY
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Due to the excellent hardenability of 18CrNiMo7-6, the sample is prone to martensitic transformation in the air, and the balanced pearlite + ferrite structure cannot be obtained.
After slow cooling, the center of the surface obtains non-equilibrium structures such as quenched martensite, lower bainite, and troostite, such as figure 1 and 2 As shown, this type of structure has a great influence on the detection of surface carbon concentration. On the basis of this type of structure, it is extremely difficult to observe grain boundary carbides, and because the core obtains non-equilibrium structures such as martensite and granular bainite, carburizing Layer depth detection data does not have any practical guiding significance
[0004] Using a complete annealing process and annealing in an electric furnace, the surface can obtain a clear balanced structure, but the annealing time is as long as several hours, which will increase the uncontrollability of carburization and cannot meet production needs
[0005] The metallographic method is used to detect the depth of the carburized layer by interrupting the sample in front of the furnace after water quenching. The detection accuracy is relatively low, and the surface carbon concentration cannot be accurately detected.

Method used

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  • Method for 18 CrNiMo 7-6 carburization furnace front-sample annealing
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  • Method for 18 CrNiMo 7-6 carburization furnace front-sample annealing

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Effect test

Embodiment 1

[0026] A kind of method for annealing before sample of 18CrNiMo7-6 carburizing furnace, comprises the following steps:

[0027] (1) Check the cast iron chips in the 100×100×150cm sample box to ensure that the cast iron chips are filled to 2 / 3 and there is no serious agglomeration. Put the sample box and the furnace sample in the test furnace and heat to 900 ℃;

[0028] (2) Take out the Φ25×25 pre-furnace sample from the furnace, cut off the iron wire binding the pre-furnace sample with a vise, and quickly bury the pre-furnace sample deep in the iron filings of the 900°C sample box, and place it in the test furnace Keep warm for 10 minutes;

[0029] (3) After the heat preservation is over, stop heating, open the furnace door, turn off the electric furnace heating, and cool naturally;

[0030] (4) When the furnace temperature cools for about 30 minutes to 650°C, close the furnace door and keep warm for 10 minutes;

[0031] (5) Take the sample out of the sample box and cool it...

Embodiment 2

[0034] A kind of method for annealing before sample of 18CrNiMo7-6 carburizing furnace, comprises the following steps:

[0035] (1) Check the cast iron scraps in the 100×100×150cm sample box to ensure that the cast iron scraps are filled to 2 / 3 and there is no serious agglomeration. Put the sample box and the sample in the test furnace and heat to 890°C ;

[0036] (2) Take out the Φ25×25 pre-furnace sample from the furnace, cut off the iron wire binding the pre-furnace sample with a vise, and quickly bury the pre-furnace sample deep in the iron filings of the 890°C sample box, and place it in the test furnace Keep warm for 11 minutes;

[0037] (3) After the heat preservation is over, stop heating, open the furnace door, turn off the electric furnace heating, and cool naturally;

[0038] (4) When the furnace temperature cools down to 660°C for about 30 minutes, close the furnace door and keep warm for 9 minutes;

[0039] (5) Take the sample out of the sample box and cool it ...

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Abstract

The invention belongs to the technical field of carburization steel annealing, and particularly relates to a method for 18 CrNiMo 7-6 carburization furnace front-sample annealing. The method comprisesthe following steps that (1), a sample box and a sample which are filled with cast iron scraps are placed in a test furnace to be heated to 890-910 DEG C; (2), the sample is rapidly and deeply buriedinto the sample box, and the temperature in a test furnace is kept for 9-11 min; (3), heating is stopped after the heat preservation is ended, and a furnace door is opened for being naturally cooled;(4), the furnace door is closed, and the temperature is kept for 9-11 minutes when the furnace temperature is cooled to 640-660 DEG C; and (5), the sample is taken out from the sample box, and air cooling is carried out. After the annealing treatment is carried out, the surface and the heart part of the carburization steel obtain balanced tissues, so that the surface carbon concentration and thelayer depth index can be accurately detected.

Description

technical field [0001] The invention belongs to the technical field of carburizing steel annealing, and in particular relates to a method for annealing a sample of a 18CrNiMo7-6 carburizing furnace. Background technique [0002] For round bar samples of the same product material, a specified number is placed in the sample hole of the carburizing furnace for each carburizing furnace, and annealing treatment is carried out 90 minutes before the end of each process cycle, and the surface carbon concentration and carburizing layer depth are detected for real-time monitoring. Carburizing process and adjustment of carburizing process, the sample is defined as the sample before the carburizing furnace. [0003] Due to the excellent hardenability of 18CrNiMo7-6 material, the sample is prone to martensitic transformation in air, and the balanced pearlite + ferrite structure cannot be obtained. After slow cooling, the center of the surface obtains non-equilibrium structures such as q...

Claims

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Application Information

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IPC IPC(8): C21D1/26C21D6/00
CPCC21D1/26C21D6/004C21D2211/005C21D2211/009Y02P10/20
Inventor 顾晓明李康康赵鑫
Owner CHANGZHOU TIANSHAN HEAVY IND MACHINERY
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