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Crusher parts bearing parts have what common heat treatment defects
2024-05-21
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The use of the process will cause localized intense wear or failure. Mostly due to the lack of heating, poor cooling or quenching operation caused by the lack of local hardness of the bearing parts exterior phenomenon known as quenching soft soft spot. Like the appearance of decarburization can cause a serious decline in the appearance of wear resistance and fatigue strength.
What are the rare thermal disposition defects of crusher parts bearing parts? What are the causes?
The service life and accuracy of the parts has an important impact, bearing parts after thermal disposal of common quality defects are: quenching microstructure overheating, underheating, quenching cracks, hardness is not enough, heat treatment deformation, appearance of decarburization, soft point, and so on. Analyze the reasons for its generation, for the guidance of the thermal disposal process and prevention has an important role.
1, overheating
To observe the microstructure. If GCrl5 steel quenching organization of coarse needle martensite, from bearing parts rough mouth can be observed after quenching microstructure overheating. But to determine exactly the level of its overheating. Then it is quenching overheating organization. The cause of the formation may be quenching heating temperature is too high or heating holding time is too long caused by overheating; may also be due to the original organization band carbide serious, two bands between the formation of low carbon area of local martensite needle thick, caused by the local overheating. Residual austenite in the superheated organization increases, and dimensional stability decreases. Due to the overheating of the quenching organization, the steel crystal is coarse, which will lead to a decrease in the toughness of the parts, the impact resistance is reduced, and the life of the bearing is also reduced. Serious overheating can even cause quenching cracks.
2, underheating
Known as underheating organization, quenching temperature is low or poor cooling will occur in the microstructure beyond the specification of the Torrhenite organization. So that the hardness of the parts decline, wear resistance is sharply reduced, directly affecting the service life of the bearing.
3, quenching cracks
Thermal stress and metal mass volume changes in the organization of stress is greater than the fracture strength of steel; four-roller crusher work appearance of the original defects (such as the appearance of fine cracks or scratches) or internal defects in steel (such as slag, serious non-metallic inclusions, white spots, shrinkage residues, etc.) quenching to form a concentration of stress; serious appearance of decarburization and carbide segregation; the lack of parts quenched tempered after tempering or not in time to tempering; the previous Work process caused by excessive cold punch stress, forging folding, deep turning marks, oil grooves sharp edges and so on. In short, bearing parts in the quenching and cooling process due to internal stress (thermal stress and organizational stress of the composite force) instantly beyond the position of the tensile strength of the material formed by the crack called quenching cracks. Causes of such cracks are: due to quenching heating temperature is too high or cooling for a long time. Causes of quenching cracks may be one or more of the above factors, the existence of internal stresses to form the main reason for quenching cracks. Quenching cracks are deep and elongated, with a straight fracture and no oxidized color on the broken surface. Bearing rings are often longitudinal flat cracks or ring-shaped cracking; bearing steel ball on the shape of the S-shaped, T-shaped or ring-shaped. The organizational characteristics of quenching crack is no decarburization phenomenon on both sides of the crack, obviously different from forging cracks and material cracks.
4, heat treatment deformation
There are thermal stress and organizational stress, bearing parts in heat treatment. This internal stress can be superimposed on each other or partially offset, complex and variable because it can be with the heating temperature, heating rate, cooling mode, cooling rate, parts shape and size, the way of the furnace changes and changes, so its heat treatment deformation is inevitable to recognize and master the rule of law can make the deformation of bearing parts (such as oval ring, size expansion, etc.) in a controlled range, conducive to the production of the normal process. The deformation is inevitable. Of course, in the heat treatment process of mechanical collision will also make parts deformation, but this deformation can be improved through the operation to reduce and avoid!
5, the appearance of decarburization
If the oxidizing medium to complete the heating, bearing parts in the heat treatment process. The appearance of oxidation will occur so that the parts of the appearance of carbon mass fraction reduction, resulting in the appearance of decarburization. The depth of the decarburized layer exceeds the depth of post-processing retention will make the parts scrapped. Determination of the depth of the exterior decarburization layer in the metallographic test can be used in metallographic method and microhardness method. Outer surface microhardness distribution curve measurement method prevails, can be used as an arbitration judgment.
What are the rare thermal disposition defects of crusher parts bearing parts? What are the causes?
The service life and accuracy of the parts has an important impact, bearing parts after thermal disposal of common quality defects are: quenching microstructure overheating, underheating, quenching cracks, hardness is not enough, heat treatment deformation, appearance of decarburization, soft point, and so on. Analyze the reasons for its generation, for the guidance of the thermal disposal process and prevention has an important role.
1, overheating
To observe the microstructure. If GCrl5 steel quenching organization of coarse needle martensite, from bearing parts rough mouth can be observed after quenching microstructure overheating. But to determine exactly the level of its overheating. Then it is quenching overheating organization. The cause of the formation may be quenching heating temperature is too high or heating holding time is too long caused by overheating; may also be due to the original organization band carbide serious, two bands between the formation of low carbon area of local martensite needle thick, caused by the local overheating. Residual austenite in the superheated organization increases, and dimensional stability decreases. Due to the overheating of the quenching organization, the steel crystal is coarse, which will lead to a decrease in the toughness of the parts, the impact resistance is reduced, and the life of the bearing is also reduced. Serious overheating can even cause quenching cracks.
2, underheating
Known as underheating organization, quenching temperature is low or poor cooling will occur in the microstructure beyond the specification of the Torrhenite organization. So that the hardness of the parts decline, wear resistance is sharply reduced, directly affecting the service life of the bearing.
3, quenching cracks
Thermal stress and metal mass volume changes in the organization of stress is greater than the fracture strength of steel; four-roller crusher work appearance of the original defects (such as the appearance of fine cracks or scratches) or internal defects in steel (such as slag, serious non-metallic inclusions, white spots, shrinkage residues, etc.) quenching to form a concentration of stress; serious appearance of decarburization and carbide segregation; the lack of parts quenched tempered after tempering or not in time to tempering; the previous Work process caused by excessive cold punch stress, forging folding, deep turning marks, oil grooves sharp edges and so on. In short, bearing parts in the quenching and cooling process due to internal stress (thermal stress and organizational stress of the composite force) instantly beyond the position of the tensile strength of the material formed by the crack called quenching cracks. Causes of such cracks are: due to quenching heating temperature is too high or cooling for a long time. Causes of quenching cracks may be one or more of the above factors, the existence of internal stresses to form the main reason for quenching cracks. Quenching cracks are deep and elongated, with a straight fracture and no oxidized color on the broken surface. Bearing rings are often longitudinal flat cracks or ring-shaped cracking; bearing steel ball on the shape of the S-shaped, T-shaped or ring-shaped. The organizational characteristics of quenching crack is no decarburization phenomenon on both sides of the crack, obviously different from forging cracks and material cracks.
4, heat treatment deformation
There are thermal stress and organizational stress, bearing parts in heat treatment. This internal stress can be superimposed on each other or partially offset, complex and variable because it can be with the heating temperature, heating rate, cooling mode, cooling rate, parts shape and size, the way of the furnace changes and changes, so its heat treatment deformation is inevitable to recognize and master the rule of law can make the deformation of bearing parts (such as oval ring, size expansion, etc.) in a controlled range, conducive to the production of the normal process. The deformation is inevitable. Of course, in the heat treatment process of mechanical collision will also make parts deformation, but this deformation can be improved through the operation to reduce and avoid!
5, the appearance of decarburization
If the oxidizing medium to complete the heating, bearing parts in the heat treatment process. The appearance of oxidation will occur so that the parts of the appearance of carbon mass fraction reduction, resulting in the appearance of decarburization. The depth of the decarburized layer exceeds the depth of post-processing retention will make the parts scrapped. Determination of the depth of the exterior decarburization layer in the metallographic test can be used in metallographic method and microhardness method. Outer surface microhardness distribution curve measurement method prevails, can be used as an arbitration judgment.
