Shandong Xinkaite Bearing Co.,Ltd.
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Address: Xu Village Industrial Garden, Gan Town, Guan County, Shandong
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Address: 314 Puli Mansion, Beixiaoxinzhuang West Street, Jinan City, Shandong
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Common quality defects in the production of Conveyor idler roller process
Clicks:3392 Date:12-11
One, soft point
Due to insufficient heating, poor cooling and improper quenching operation, the phenomenon of partial hardness on the surface of Conveyor idler roller parts is called quenching soft spot. Like surface decarbonization, it can cause a serious decrease in the wear resistance and fatigue strength of the surface. Conveyor idler roller parts are quench cracks due to internal stress during quenching and cooling. Causes of the cracks are: the quenching temperature is too high or too fast cooling, heat resistance and fracture strength of metal quality of volume change stress greater than steel; the original defects of working surface (such as surface micro crack or scratch) or internal defects (such as steel slag, serious non metallic inclusions white spots, and shrinkage etc.) formed in the quenching residual stress concentration; surface decarburization and carbide segregation; parts after quenching and tempering is insufficient or not timely tempering; caused by cold punching processes in front of large stress, forging folding, turning deep marks, sharp edges and other oil groove. The quenching crack is deep and slender, the fracture surface is straight, and the broken section has no oxidation color. The microstructure of the quenching crack is characterized by no decarburization on both sides of the crack, obviously different from the forging cracks and material cracks. In a word, the cause of quenching cracks may be one or more of the above factors. The existence of internal stress is the main reason for the formation of quenching cracks. On Conveyor idler roller ring, it tends to be straight cracks or circular cracks. The shape on Conveyor idler roller steel ball has S shape, T shape or ring type.
Two. Less heat
Three. Overheating
Four, quenching crack
If Conveyor idler roller parts are heated in oxidizing medium during the heat treatment process, the surface will oxidize, reduce the surface carbon content of the parts and cause surface decarburization. Determination of surface decarburization depth in metallographic examination of available metallographic and micro hardness method. The depth of the surface decarburization layer exceeds the remaining amount of the final processing, and the parts will be discarded. The method of measuring the surface microhardness distribution curve is accurate, and it can be used as the arbitration criterion.
Five, surface decarbonization
Six. Heat treatment deformation
If quenching temperature is low or the cooling is bad, it will produce more than the standard tortuor structure in the microstructure. It is called the sub thermal structure. It will make hardness decrease, wear resistance will decrease dramatically, and affect the life of Conveyor idler roller.
Conveyor idler roller parts during heat treatment, there is thermal stress and stress, the internal stress can be overlapped or partially offset, is complex, because it can change with the change of heating temperature, heating rate, cooling mode and cooling speed, shape and size, so the heat treatment deformation it is inevitable. Understand and grasp the change rule of it can make Conveyor idler deformation of roller parts (such as rings, elliptic dimension expansion etc.) in the scope of control, is conducive to the production of. Of course, the mechanical collision in the heat treatment process also causes the parts to be deformed, but the deformation can be reduced and avoided by improved operation.
The microstructure overheating after quenching can be observed from the rough port of Conveyor idler roller parts. But to determine the degree of overheating, microscopic structures must be observed. If the coarse needle like martensite appears in the quenched structure of GCr15 steel, it is the quenching and superheated tissue. Excessive heat can even cause quenching cracks. Because of the overheating of the quenched structure and the large crystal of the steel, the toughness of the parts will be reduced, the impact resistance is reduced, and the life of Conveyor idler roller is also reduced. The retained austenite increased in the superheated tissue and the dimensional stability decreased. The cause may be the quenching heating temperature is too high or the holding time is too long, causing the overall overheating; it may be because the original organization banded carbide serious, low carbon in the area between the two belts forming local acicular martensite thick, local overheating
