Mould Steel HPM75 Tool Steel

• Machining analysis of HPM75 non - magnetic steel

HPM75 nonmagnetic steel is a special material, because its alloy composition contains a large amount of alloy carbide, which strengthens the matrix of nonmagnetic steel. However, the common drill bits and tools used in our cutting are poor in heat resistance, wear resistance and hardness.

When the cutting speed of HPM75 nonmagnetic steel is low, the cutting bottom of the material and the rake face of the tool form a new material surface with high chemical activity in the cutting process. Under the action of high temperature and high pressure, the surface of the material will produce debris flow. The chip flow is relatively stable on the surface of the material, but when the vibration or load is uneven during cutting, the chip flow will fall off and cause tool wear. The chip flow beyond the blade will replace the blade for cutting, which will leave a mark on the surface of the processed material and affect the machining accuracy.

When the HPM75 non-magnetic steel die is subjected to intense pressure and impact pressure in the drilling process, the austenitic structure of non-magnetic steel is easy to transform into fine grain martensite, and the hardness of non-magnetic steel material is increased from the original 200HB (about 20HRC) to about 550HB (about 55HC). At the high temperature formed by friction and extrusion, the material surface is easy to form a high hard oxide layer (Mn2O3), but also makes the material thermal conductivity is very low (about 25% of S45C die steel), less heat emission. In this way, the bit is easy to annealing, resulting in cutting edge collapse, thereby affecting tool life.