Causes of quenching distortion and cracking of the linear cutting
1, the structure of parts
(1) the long and narrow shape cavity, lug parts easy to distortion, distortion and complex shape, the ratio of length to width, cavity and the border width ratio. More complex shape, length width ratio and the cavity with the border width is bigger, bigger distortion. Distortion rule is cavity central sag, and the convex block is usually warping.
(2) cavity quenching complex shape, easy to produce crack in the corner, and even prone to cracking, its occurrence with the material composition, heat treatment process.
(3) cylindrical thin wall parts, if the wall is cut, easy to produce distortion, are generally round to oval; if the cutting gap, easy to produce cracks in the cut through time.
(4) from the outside into the deep notch easy distortion, distortion of mouth adduction, depth and material distortion and notch on the properties of the.
2, heat processing
(1) blank in the forging of initial forging temperature is too high or too low, the final forging temperature is low and easy to produce distortion and cracking;
(2) the final forging temperature is too high, the grain is too large, the final forging cooling speed is too slow, with reticulate carbide parts easy to distortion and cracking;
(3) forging no spheroidizing annealing, spheroidal pearlite more than 5 parts easy distortion and cracking;
(4) high quenching temperature, austenitic grain bulky, will reduce the strength and toughness, brittleness material increase, but also easy to produce distortion and cracking;
(5) not timely tempering quenching or tempering inadequate prone to distortion and cracking;
3, mechanical processing technology
(1) die larger area, middle area resection without any prior hollowed out, with larger cut frame, the frame size will be changed.
(2) no appearance of threading hole where the starting point blank, blank from the outside to cut, no matter how the bump tempering and shape, are generally easy to distortion, especially the quenching cracking more heavy, even in cutting.
(3) grinding heat treatment, such as no requirement for grain size, feed rate, cooling way, after surface grinding burn and cracks are easily generated distortion and cracking
4, material
There are serious segregation of carbide and the hardenability of the material difference;
5, line cutting process
(1) the path selection cutting improper;
(2) the workpiece clamping method is not reliable, the improper selection of pinch point;
(3) the selection of electrical parameter;