Rolling bearing parts formed due to stress during the quenching process of quenching crack of crack. Caused this crack of causes has: due to quenching heating temperature high or cooling too rush, hot stress and metal quality volume changes Shi of organization stress is greater than steel of anti-break strength; work surface of original defects (as surface micro-crack or classified marks) or steel internal defects (as clip slag, and serious of non-metallic clip debris, and white, and shrinkage residual,) in quenching Shi formed stress concentrated; serious of surface off carbon and carbide partial analysis of; parts quenching Hou tempered insufficient or is not timely tempered; front processes caused of cold rushed stress had large, and Forged folding knife sharp edges, oil ditch, deep turning and so on. In short, resulting in quenching cracks could be due to one or more of the above factors, the main cause of stress is the formation of quenching crack. Quenching crack deep, slender, fracture, straight and cutting plane no oxidation. It is often straight vertical crack on the bearing ring or annular cracks; on steel ball bearings, in the shape of s-shaped, t-shaped or annular. Characteristics of quenching crack is cracked on both sides without removal, significant differences and forging crack crack and material.
When scrolling in heat treatment of bearing parts, heat stress and organizational stress, this stress can overlap each other or partially offset is complex because it can speed, cooling, heating and cooling heating temperature, speed changes, changes in the shape and size of the part, so heat treatment deformation is unavoidable. Understand and master it can make the change of SKF bearings part of the deformation (the oval ring, size up, and so on) at the range of controlled, productive. Of course in the heat treatment process of mechanical collision also cause a deformation of parts, but this variant is could be reduced by improving operations and avoid.
During heat treatment of bearing parts, if it is heating in oxidizing medium, surface oxidation can occur so that the part surface carbon content reduced, resulting in removal of carbon from the surface. Surface decarbonization layer depth over the last scrap of machining allowance for the parts. Determination of surface decarbonization layer depth available in the metallographic examination of metallographic method and micro-hardness method. The surface microhardness distribution curve measurement shall prevail, can do arbitration criterion.
Due to insufficient heating, poor cooling, hardening rolling bearing parts as a result of improper operation of inadequate surface hardness phenomenon called quenching soft points. It to the removal of carbon from the surface can cause surface wear resistance and fatigue strength of serious decline.
Are the main factors for adjusting the installation, use and maintenance, repair and maintenance, according to technical requirements. Bearing installation conditions are used as one of the factors is often results in incorrect state changes between each part of the installation package of the loading capacity of the primary factors, abnormal operation and early failure. According to FAG bearings for installation, use, maintenance, maintenance of technical requirements for the operation of rolling bearings-contact load, speed, temperature, vibration, noise and lubrication State monitoring and inspection, find immediately find the cause of the exception, to adjust back to normal.
Materials for rolling bearings of metallurgy is the main factor affecting the quality of early failure of rolling bearings. With the advances in metallurgy (such as roller bearing steel, vacuum degassing, etc), improved the quality of raw materials. Raw materials quality factors in the failure analysis of rolling bearing′s share has declined significantly, but it remains one of the main factors of NSK bearings failure. Options is appropriate are necessary rolling bearing failure analysis.