40Cr of China GB standard steel, 40Cr steel machinery manufacturing industry one of the most widely used steel. Quenched and tempered with good mechanical properties, good low-temperature impact toughness and low notch sensitivity. Steel hardenability, water quenching hardenability Ф28 ~ 60mm, the oil quenching hardenability to Ф15 ~ 40mm. This steel is suitable for cyanide and high frequency quenching treatment except quenched and tempered. Machinability better, when the hardness HB174 ~ 229 to 60%,cutting wheel, relative machinability. The steel is suitable for the production of medium-sized plastic molds.
1, the process seems to be wrong ah! The annealed hardness ≤ 207HBS 40Cr hardness after quenching and tempering is about HRC32-36, that is probably HB330-380 Why not annealed drilling, insisted to the quenched and tempered after drilling. If you really want it in the post-drilling Select carbide drill.
Reaming should choose a slow speed, feed rate slower cutting fluid oil.abrasive tools
3, a reasonable choice of the angle of twist drill geometry processing of 40C material. Best grinding group drill, countersink holes drilled.