Isothermal normalizing technology of carburized gears steel forging

A technology of isothermal normalizing and carburizing gears, applied in the field of metal heat treatment, can solve the problems of unfavorable machining, low pass rate, uneven hardness, etc., to avoid banded structure and abnormal structure, high production efficiency, and small hardness fluctuation Effect

Active Publication Date: 2009-02-11
JIANGSU PACIFIC PRECISION FORGING
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Problems solved by technology

[0007] (3) Uneven hardness and low pass rate
[0009] At present, normalizing heat treatment in my country's normalizing production line (including isothermal normalizing) inevitably produces oxidative decarburization. If machining is performed after normalizing, oxidative decarburization can be eliminated in subsequent machining, but Jiangsu Pacific Precision Forging Co., Ltd. adopts the most advanced cold precision forging forming technology. The gear tooth surface formed by precision forging is no longer processed. In addition, in order to facilitate cold precision forging before cold precision forging, spheroidizing annealing technology is used, which is beneficial to the subsequent The machining is not good

Method used

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Embodiment Construction

[0014] The present invention is further illustrated below by way of examples.

[0015] All process operations are carried out automatically under the control of PLC except manual loading.

[0016] 1. Loading: Load the gear workpiece into the material box and hoist it to the roller rod of the feeding table. The material box moves forward with the rotation of the roller rod.

[0017] 2. When the material box enters the front vacuum chamber, the PLC controls the 1# vacuum pump to evacuate it. When it reaches 133.3Pa, it will automatically stop and fill with nitrogen. When the air pressure reaches normal atmospheric pressure, it will automatically stop filling nitrogen.

[0018] 3. The material box enters the normalizing heating furnace, and the material box completes the process of preheating, heating, and heat preservation according to the set speed. The preheating is heated from normal temperature to 200 ° C, and the normalizing heating is from 200 ° C within 120 to 150 minutes...

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PUM

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Abstract

The invention discloses an isothermal normalizing process of a carburized gear steel forging stock, which relates to the technical field of metal heat treatment. The process is carried out on a bright isothermal normalizing production line under a preevacuated and fully electrically heated roller bottom protective atmosphere. The heating, heat preservation, fast cooling, isothermy and water cooling in the protective atmosphere are automatically completed by a PLC control. The normalizing heating temperature of the forging stock is Ac3 plus (100-150) DEG C, and the temperature is kept for 36-45min, and the forging stock is quickly cooled to 560-600 DEG C within 10min by high-purity nitrogen gas blown by an electric fan. The normalizing process has the advantages of normative operation, high production efficiency, and can ensure that the forging stock is not oxidized and decarburized in the heat treatment process, and austenite crystals in the forging stock are evenly distributed, which avoids the appearance of banded structures and causes the forging stock to have good and stable quality with small hardness fluctuation.

Description

technical field [0001] The invention relates to a metal heat treatment method, in particular to an isothermal normalizing process for a gear forging blank made of carburized gear steel. Background technique [0002] According to the definition of normalizing in GB7232 and GB / T16923: normalizing (including ordinary normalizing, two-stage normalizing and isothermal normalizing) is to heat the steel to 30-50°C above Ac3, keep it for a proper time, and then leave it at rest Or cooling in flowing air (two-stage normalizing cooling to Ar1 and then slow cooling, isothermal normalizing for fast cooling to a certain temperature in the pearlite transformation zone, so as to obtain pearlite structure and then air cooling) process. [0003] The main purpose of normalizing is to normalize steel parts with abnormal microstructure and obtain a relatively stable and normal microstructure. Due to the different types and shapes of processing objects and abnormal microstructures, the requirem...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D1/28
Inventor 夏汉关赵红军包文慧张立平沫桂萍王耀祖
Owner JIANGSU PACIFIC PRECISION FORGING
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