High strength steel and high strength steel, due to the different amounts of alloying elements, after heat treatment, Si, Mo, Ni, and other elements to make the solid solution strengthening, microstructure to martensite, having high strength (up 1960MPa) and high hardness (HRC> 35), impact toughness is higher than 45 steel cutting has the following characteristics:
1) the tool wear, durability: high-strength steel and ultra-high-strength steel, the hardness after quenching and tempering is generally HRC50 below, but the high tensile strength, toughness Hao. In the cutting process, the length of contact of the tool and chip is small, the concentration of the stress and the heat of the cutting zone, easily lead to the rake face crater wear, cutting wheel,increased flank wear, leading to edge chipping missing or burns low, the durability of the abrasive tools.
2) cutting power: the shear strength of high-strength steel and ultra-high-strength steel, difficult deformation, cutting forces than the cut of 45 steel units under the same cutting conditions cutting force of 1.17 to 1.49 times.
3) cutting temperature high: the poor thermal conductivity of the two steels, cutting chips concentrated on the the the edge nearby small contact surface, so that the cutting temperature increases. 45 steel thermal conductivity was 50.2 W / (m · K), rather 38CrNi3MoVA thermal conductivity coefficient of 29.3 W / (m · K), only 60% of the 45 steel, the cutting cutting 38CrNi3MoVA temperature than cutting 45 No. steel cutting high temperature of 100 ℃. High cutting temperature, tool wear increased.
4) chip breaking difficulties: the high-strength steel and ultra-high-strength steel with good ductility and toughness, so cutting chip is not easy to curl and break. The chip is often wrapped around the workpiece and tool, affecting the smooth progress of the cutting.
Drill drilling high-strength steel and ultra-high-strength steel, how to choose?
Drilling high strength steel, the choice of high-performance high-speed steel twist drill or carbide drill. Drilling ultra-high-strength steel, the general should be used carbide drill diameter greater than 16mm hole, recommended use indexable drill with.cutting disc
High-speed steel twist, the choice of the group of three sharp edge shaped drill drill or repair ground. In order to improve the rigidity of the drill should be appropriately increase Zuanxin thickness, to reduce the amount of overhang. Helix angle should also be smaller, and is generally 17 ° to 30 °.cutting wheel
Choice carbide drill, you can increase the angle, to improve chip removal and general of for 2kr = 140 ° to 150 °. Should be reduced in order to reduce the axial force to the chisel, drill diameter is generally 0.1do (do). The drill feed the anterior horn gf = 0 ° to feed posterior horn af = 6 ° to 12 °. Indexable drill with a blade should be used in coated blade and non-blade coating. Recommend use of coated inserts: YB01, YB02, YB03; non-coated blades: YC10, YC30, YC40, YD20, 798,813, etc..