B. Select

Calculated according to the effective thickness of 2mm for 1h, which coupled with a correction value (consider the power of the stove, furnace size, installed furnace mode and installed furnace capacity), the last set holding time:

6202 ~ 6205 bearing blank: 4h outer, inner 4.5h, large set of installed 5h??.

6206 to 6406 bearing the rough: the outer ring 4.5h 5h inner large set of installed 5h??.

In order to achieve the above holding time, holding temperature rose to 720 ℃ hot 1h, you can reach the organization changes in full within a certain range. Allows the operator to increase 0.5h annealing the box Jia Gaijia mud seal the actual case.

(3) the choice of cooling rate

To finally get the appropriate organization largely depends on the cooling rate. Cooling at different speeds, you get the performance of different organizations. Pearlite spheroidization annealing cooling occurs if the cooling rate, the resulting morphology of pearlite, carbide shape, size, distribution is not the same cooling rate, large, small, dispersed carbides, general hardness partial high cooling rate is small, coarse carbide particles, the low hardness.

Globular pearlite formation of the required cooling rate is generally controlled at 10 ~ 30 ° C / h, can be used in order to ensure the quality of the ball of the cooling rate of 15 ~ 20 ° C / h as standard. In the actual production process, the furnace insulation performance at room temperature a great influence on the general cooling rate close to the room temperature, based on seasonal temperature, the preparation of two processes. Or according to the task is urgent, allow 500 ℃ released, the following out-of-the-box 300 ℃. The hermitages of aluminum silicate fiber felt box-type furnace, the furnace door and the box between the aluminum silicate fiber felt a wall to prevent the door heat, reduce the temperature difference. Packing Jiagai Jia mud seal into the furnace, should ensure that the gap between the annealing box should be at least 20mm, should be more than 50mm clearance between the annealing box with electric.

Spot checks in the blast furnace, the furnace and the furnace after the three boxes on the extraction, and the lower 9 parts for routine examination. The general GCr15 bearing steel rough forgings annealed hardness HRB88 ~ 94 4; fibrous tissue decarburized layer depth of 0.2 ~ 0.3mm, annealing quality can reach JB/T1255 ~ 2001 high-carbon chromium bearing steel bearing parts heat treatment conditions the requirements of .


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