| 摘要 |
PURPOSE:To obtain the material for springs which is relieved in notch sensitiveness, is improved in fatigue resistance and has good workability by tempering the material to the hardness distribution in which the peak of hardness is formed on the surface layer part and the hardnesses on the surface and central surface are smaller than the above-mentioned peak value. CONSTITUTION:This material for springs is so tempered as to have the hardness distribution in which there is the peak of the hardness on the surface layer part and the hardnesses on the surface and the side nearer the center than the surface layer part are both smaller than the above-mentioned peak value. Said material has the excellent fatigue resistance and ductility and can be easily formed to springs, etc. The above-mentioned hardness distribution is preferably set at l1>=2l2 when the distance from the surface to the point where the hardness begins to change is designated as l1 and the distance to the peak position of the hardness as l2. Further, such a hardness distribution that the peak position of the hardness is between the peak position of the residual compressive stress imparted by shot peening and the position to generate the max. stress at the time of using the spring is more preferable. |
