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Shot Peening Process

QINGDAO KNNJOO MACHINE INC. | Updated: Mar 03, 2016

First,purpose : to avoid high shot to make parts of surface residual tensile stress , compressive stress and improve the fatigue strength.

Second, the use of: general steel parts using the temperature exceeds 260 ℃, aluminum parts using the temperature exceeds 170 ℃, do not need to shot peening . Because the temperature is too high , the stress generated by shot peening will eliminate lost the desired effect.

Third, the process :

1 . Pills Type selection:

( 1 ) steel shot hardness is generally HRC40 ~ 50, when machining hard metals can be to raise the hardness to HRC57 ~ 62. Steel balls toughness, widely used, its life as iron pills several times.

( 2 ) the hardness of iron pills is generally HRC58 ~ 65, brittle and easily broken, life is short, widely used, mainly for high- need peening intensity of the occasion.

2 . Shot size selection:

( 1 ) shot granularity generally use between 6 to 50 mesh , the higher strength requirements blasting , shot peening particle size is relatively increased.

( 2 ) Shot peening is also affected by the choice of size limitation process part shape , the diameter of the groove should not exceed half the diameter of the circle . Usually the greater the shot , greater impact energy , the greater the intensity of shot peening , the peening coverage but lower . Therefore, under the premise to produce the desired peening intensity , to minimize the size of the shot peening is advantageous . 

3 . Shot peening using common hardness greater than the hardness of the hardness of the part. When the hardness greater than the hardness of the part, the change does not affect the hardness of shot peening intensity . Conversely , to reduce hardness blasting , shot peening intensity will decrease .

4 . Jet velocity

Shot speed increased, shot peening intensity will increase, but the speed is too high will increase the amount of blast fragmentation . Shot increase consumption.

5. When adjusting the angle of the jet is vertical , shot the highest intensity , so generally this state land-line shot peening . If the shape of the affected parts restrictions , small-angle shot when necessary , should be appropriate to increase the size of shot peening speed .

6. Broken low amount of shot peening shot crushing strength , and therefore often remove broken pills , to ensure the full rate of not less than 85% of the shot .

7 . Shot peening time to time due to the number of shot peening process results in the workpiece may be generated , in principle, to achieve the desired peening intensity . ( Typically 30 minutes ) Also to note is shot mostly in the United States is now the strength of SAE Standard J442 said Almen arc height gauge measurement. Almen arc height gauge is 2.4mm thick 0.8,1.3 standard size or 70 carbon steel, the hardness of HRC44 ~ 50, this sample is set on the fixture, its shot peening one side , then the arc high measuring curved steel arc height of the sample can be derived peening intensity . 


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