Forging dies and forging blanks, like other mechanical parts, are manufactured by cutting, electromachining, forging, rolling, extrusion, welding, casting, grinding or polishing. Different machining methods can cause different surface corrugations and roughness of parts.
1. Corrugations
The waviness is defined as the geometric shape formed by the peaks and troughs of periodic waves (FIG. 7-2-1). The wavelength of the corrugations is much larger than the height of the corrugations, usually more than 40 times the ratio. The corrugations are often caused by uneven cutting feed, uneven cutting force or machine vibration; It has some effect on friction, but it's not important.
2. Surface roughness
Figure 7-2-2 shows the surface roughness profile diagram. Roughness refers to the uneven surface in a short distance (usually 2Mm~800Mm). Roughness is usually the most important surface feature in tribology research.
There are many kinds of evaluation parameters to represent surface roughness (see Figure 7-2-2), among which the common ones are: The arithmetic mean deviation island of the contour (arithmetic mean of the absolute value of the contour skew), the 10 point height house of the microscopic roughness (arithmetic mean of the sum of the average of the five largest contour peak heights and the average of the five largest contour peak valleys), and the maximum contour height Rmax (between the contour peak top line and the valley bottom line) ), the average distance Sm (average distance of contour microscopic irregularity), the average distance S (average distance of contour unimodal distance), and the ratio of contour support length (ratio of contour support length to sampling length). For the meanings of each parameter, refer to the national standard GB 3503-83. In addition, the root mean square deviation of the contour is also commonly used to evaluate the surface roughness.
Among the many parameters described above to represent surface roughness, the most commonly used parameters to evaluate the roughness of forging die are the arithmetic mean deviation of the contour (island) and the ten point height of the microscopic roughness (block). The island is preferred for the surface roughness of die bore, and its common parameter range is RaO.% m? 0. Ijzm, which is equivalent to ▽ 7? Del 10.
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