| 摘要 |
PROBLEM TO BE SOLVED: To enable the production of a product having deep holes and a good metal flow with a good yield excellent productivity by forging while controlling the coefficient of friction at the contacting part between a metallic material and a tool to keep a prescribed level, in the case of boring the deep hole having the specific value of the ratio of the boring depth to the product height by the use of the tool, such as a punch, to the metallic material. SOLUTION: At the time of forging which includes boring of the deep hole having 0.5-1 as the ratio of the boring depth (d) to the product height (h), by applying the tool such as the punch to the metallic material, the forging is executed while keeping the friction coefficient to the range 0.3 or less along the contacting part between the metallic material and the tool. After coating oil lubricant 8 on the metallic material 7, and boring the hole 9 with the forging tools 10, 11 before product-working, the tools and the work material are again coated with the lubricant before applying the working process. In this way, the lubricating effect is kept without coming short of lubrication, and further, service life of the tool is extended and the surface characteristics of the product is improved.
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