First, the centre offset method
1, the imported bearing collar inner and outer diameter of the rescue
First of all, the parts exist in the various defects (asymmetric type) size for accurate measurement, calculated which the small amount of grinding (to the finished product size deviation when the amount of grinding) M, and then in the grinding of the parts for the centre offset (to make the defects increase the amount of grinding in the direction of the offset), the large amount of offset for M/2, that is, the defects of the relative increase in the amount of grinding, focusing on the grinding,.
2, on the collar inner and outer raceway salvage
Import bearing collar grinding design benchmark for the inner diameter or outer diameter, that is, the first grinding inner (outer) diameter after grinding raceway, within the circle as an example, if there is asymmetric type defects in the inner raceway, it is necessary to accurately measure the size of the inner diameter of the part, and calculate the Z large amount of grinding M, as well as the large amount of grinding at the defective inner raceway M1. when M1 < M, in the grinding of the inner circle in the centre of the need to offset, the large amount of offset is M1/2, that is, in the processing of That is, in the processing of the inner diameter to the inner raceway defects in advance relative increase in the amount of grinding, and then grinding the inner raceway, the defects will be focused on grinding, scrap can be saved. When M1 ≥ M, normal grinding can not be removed, according to the situation can be used to save the method described in section 1.1.
Adopting the centre offset method of grinding is carried out under the premise of ensuring the hardness of the parts and the depth of the carburised layer, the total offset cannot be completed in one offset grinding, and it is generally divided into several times of grinding, i.e., it is completed by the repeated process of offset trial grinding-measuring-adjusting the offset-retrying grinding again, and when the defects are ground off, the defects are Re-alignment and normal grinding to correct the ovality. The efficiency of this method is low, and at the same time requires the operator to have a high level of technology, but in a single machine, single piece production using this method to save the success rate is high, without delaying the production schedule. After several years of practical verification of good results.
Imported bearing steel quenching organisation by the quenched martensite, a small amount of undissolved secondary carbides and about 12% to 14% of the residual austenite. Quenched martensite and residual austenite belongs to the unstable organisation, the decomposition of martensite in the tempering process so that the volume of steel contraction, and the decomposition of residual austenite so that the volume of steel expansion.
With the increase in tempering temperature, the amount of residual austenite transformation decomposition increases, in order to ensure that the process requirements of the hardness conditions, appropriate increase in tempering temperature, so that the residual austenite decomposition, transformed into a larger volume of martensite organisation, the volume of the workpiece can be correspondingly increased, that is, the relative amount of the OD mill to increase the use of this method can be made to make imported bearings collar defects in the normal grinding conditions to become a scrap part can be rescued.
This method for residual austenite content of thick, heavy workpiece (especially for spherical roller imported bearings) more significant effect. Actual production for different specifications, different sizes, different thickness of the parts developed a different tempering process, under the premise of ensuring the hardness and deformation, so that the organisational transformation is sufficient to produce a larger up shape, and accordingly increase the amount of grinding, save scrap.
For dimensional tolerances beyond the design standard imported bearing parts, chemical deposition method can be used to save. The principle of chemical deposition is through a variety of chemical materials between the chemical reaction, uniformly on the surface of the parts to produce a certain thickness of the metal coating, through additional tempering to ensure that the metal layer and the parts of the original hardness and mechanical properties of the same. Chemical deposition only increases the size of the part size, does not change the shape of the part tolerance, so for the size of the part tolerance exceeds the poor, the use of chemical deposition is an effective method of salvage, at present, the thickness of unilateral deposition up to about 0.1mm.