Process of utilizing afterheat of casting in reducing stress ageing treatment

Abstract

The invention discloses an aging treatment process for reducing casting residual stress by utilizing the residual heat of castings. The method and steps are: unpack the casting at 300-800°C, remove the pouring riser, sand core, and molding sand, put it into a continuous heat treatment furnace at 300-600°C, and continuously heat up to Keep warm at 450-650°C for 1-8 hours, then slowly cool to 200°C at a rate of less than 30°C per hour, take out the oven and cool to room temperature. The casting residual stress of the casting is less than 60MPa, which meets the requirements of diesel engine castings. And the prior art is: after the casting is unpacked and cooled to room temperature and cleaned, the furnace is loaded to reduce the casting residual stress aging treatment. The invention saves the energy and time for raising the temperature of the casting from room temperature to 300-600 DEG C, reduces the cost and improves the efficiency. The cost of the present invention is reduced by 0.638 yuan / kg compared with the traditional process of using a box-type furnace, and the reduction rate is 78.3%.

Description

technical field [0001] The invention relates to a ferrous metal stress-reducing process, in particular to a casting residual heat stress-reducing aging treatment process and method for castings produced by a continuous mechanized casting production line. Background technique [0002] Commonly used traditional processes for stress-relief aging heat treatment of castings are: [0003] Open the box → cool down to room temperature, remove the riser and molding sand, sand core, polish and remove the top → stress-reducing aging heat treatment. [0004] Stress-relief aging heat treatment is aimed at reducing casting residual stresses in castings. The principle is to reheat the casting to 530-620°C, use plastic deformation to reduce the residual stress, and then slowly cool it in the furnace to obtain a casting with a smaller residual stress than the original one. This is the most commonly used heat treatment for gray iron castings. See attached figure 1 . [0005] In the case of...

AI Technical Summary

Problems solved by technology

[0018] (3) Influence and harm of casting residual stress on iron castings

[0023] 2. Lead to cracking of cast iron parts

[0029] 3. Increase the difficulty of machining and increase the wear of the tool

But the electric furnace is easy to control, with high degree of automation and less pollution

[0063] 3. For the case where there is a large residual stress value in the casting, it is not suitable to adopt vibration aging treatment

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