Enhanced shot blasting machine, shot blasting process basic three parameters
Qingdao Donghailin-professional shot blasting machine manufacturer, now, provides you with three basic parameters for strengthening the shot blasting machine:
The first parameter: blasting strength
1. The process parameters that affect blasting strength include: projectile diameter, elastic velocity, projectile flow rate, shot peening time and so on. The larger diameter of the projectile, the faster the speed and the greater the momentum of the collision between the projectile and the workpiece, the greater the intensity of shot peening. The residual compressive stress formed by shot peening can reach 60% of the tensile strength of the part material. The residual compressive stress layer can usually reach a depth of 0.25mm and the limit value is about 1mm. The shot peening intensity needs a certain shot peening time to ensure that after a certain period of time, the shot peening intensity is saturated, and then the shot peening time is extended, and the strength is no longer significantly increased. In the shot blast strength of the Almen test, the shot peening strength was characterized by the deformation of the test piece.
2.In the Almen test, the shot peening strength was usually measured using N-pieces (for non-ferrous metals), A-pieces (quite commonly used), and C-pieces (higher intensity). The A and C specimens were measured. The relationship is approximately 3 times. For example, the strength of 0.15-0.20Cmm measured with the C-test piece is equivalent to 0.45-0.60Amm. In the figure, C is a thick test piece. In the thin A test piece, the original deformation of the test piece is measured first, and then the work piece that clamps the test piece is placed in the blasting box. The same process as the workpiece is performed. injection. After shot peening, remove the test piece and measure the height of the deformation arch.
The second parameter: blast coverage
1.The coverage rate refers to the number of times each point on the workpiece is hit by the steel shot. Some people think that the coverage rate of shot peening is that if I spray the workpiece 2 times on the nozzle 1, can I meet the coverage of 200%? ? It sounds reasonable at first glance, but this is not the case. Coverage is measured by applying a layer of colored glaze or fluorescent glaze on the surface of the workpiece, and then blasting the workpiece according to the process parameters. The workpiece is removed once per spray surface and the residue is observed under a microscope (magnifier). The proportion of the coating on the surface, if there is still 20% remaining, the coverage is 80%. When the residual is only 2%, that is, the coverage is 98%, it can be regarded as all ***, that is, the coverage is 100%, and there is a time. If you reach 400% coverage, this is 4 times the time.
2.Coverage factors, factors affecting coverage include hardness of the part material, diameter of the projectile, spray angle and distance, and shot peening time. When the hardness of the part is less than or equal to the hardness of the standard test piece, the coverage rate can reach 100% under the specified shot peening intensity; otherwise, the coverage rate will decrease. At the same projectile flow rate, the longer the distance between the nozzle and the workpiece, the smaller the angle of injection, and the smaller the diameter of the projectile, the shorter the time required to reach the coverage rate. For shot peening, the appropriate size of projectile, spray angle and distance should be selected so that shot peening strength and coverage can reach the required value at the same time.
The third parameter: surface roughness
1 Due to the injection of steel shots, the workpiece surface roughness has a certain change. The factors affecting the surface roughness are the strength and hardness of the part material, the diameter of the projectile, the angle and velocity of the jet, and the original surface roughness of the part. Under the same other conditions, the higher the strength and surface hardness of the part material, the more difficult the plastic deformation, the shallower the crater, the smaller the surface roughness value; the smaller the diameter of the projectile, the slower the speed, and the shallower the crater, The surface roughness value becomes smaller; the injection angle is larger, the smaller the normal component of the projectile velocity, the smaller the impact force, the shallower the crater, the greater the tangential velocity of the projectile, the greater the abrasive effect of the projectile on the surface. The smaller the roughness value;
2.The original surface roughness of the part is also one of the influencing factors. The rougher the original surface is, the smaller the surface roughness value is after shot blasting. On the contrary, the smoother the surface is, the surface becomes rough after shot peening. When high-strength shot peening is performed on the parts, the deep crater not only increases the surface roughness value, but also forms a large stress concentration, which seriously weakens the shot peening effect.