| 摘要 |
PROBLEM TO BE SOLVED: To reduce the weight and easily form internal threaded holes by applying surface hardening treatment to respective large end parts divided into the main body side and the cap part, and making the divided face on the main body side to be a non-hardened part. SOLUTION: A large end part 12 integratedly formed by casting or forging is divided into the main body side 13 and the cap part 14, and the divided face 27 on the main body side 13 directly after division is extendedly formed in the direction of the cap part 14 than the final divided face 18 by a thickness portion corresponding to a dummy part 28. Next the main body side 13 and the cap part 14 are treated by a customary cementation/quenching method, so as to form surface hardening treated layers 25, 26. In this case, the surface hardening treated layers 25, 26 are also formed on the divided faces 16, 27 and the insides of through holes 17. Next the dummy part 28 is removed, and the divided face 18 is made into a non-hardened part of non- cementation layer. Then by working a prepared hole 19 and an internal threaded hole from the divided face 18 in the rod direction through a thick wall part, the main body side 13 fitted for a nutless type connecting rod is obtained. Hence the internal threaded holes 20 can be easily formed, and the main body side 13 of good mass production efficiency can be realized. |
