Zhengzhou Gou's induction heating equipment manufacturer talks about the heat treatment of aviation drill bit bars

The ultra-long drill bits produced by a certain company are exported to Boeing Company in the United States and are commonly known as aviation drills. It is just a round bar when quenched and then ground into shape. The material is M2 steel, the bar size is 3-8mm x 150-400mm, the technical requirements are the hardness of the blade 63.5-67HRC, the handle 35-50HRC; overheating is not allowed; straightness ≤0. 10mm. This type of product is characterized by a slender shape, measuring 3.0mm x 400mm, and an aspect ratio d/L>100. It is particularly easy to bend during the heat treatment process. For this reason, in addition to the heat treatment process, relevant aspects should also take measures to reduce bending.

① Increase the grinding allowance from the conventional 0.5 -0.6mm to 0. 80 - 1.Omm.

② Straighten after punching, the straightness is ≤0.10mm.

③ Straighten one by one before quenching, the straightness is ≤0.10mm, and remove stress.

1) Heat treatment process.

①Preheat. Choose a suitable 3-layer plug-in clamp (two-layer clamp with a length of less than 200mm). The upper, middle and lower holes must be aligned, and no misalignment is allowed. Dry the water in a special well-type resistance furnace, about 550gC x 30min, preheating temperature is 880-900℃, double-plate preheating, preheating time is twice the heating time, and the handle end is exposed to the liquid surface by 25-30mm.

②Heating. The heating temperature is 1 205 - 1 21℃.

③Cool. Classify in a neutral salt bath at 580℃-620℃ for about 30 seconds, immediately put in nitrate salt at 240-280℃ and isotherm for 2 hours. It is better to control the metallographic grade at level 10.5.

④ Straighten. Air-cool the isothermally baked workpiece to room temperature, immediately clean it with hot water, and straighten it piece by piece, with a straightness of ≤0.10mm.

⑤Tempering. Tighten the straightened bars with special movable clamps. The diameter of a single bundle is preferably <80mm. The tempering temperature is 540-550°C, kept for 1 hour, and tempered 4 times.

⑥Inspection. After flat grinding, the hardness is 63.5-67HRC as qualified; the tempering degree is ≤2 levels; overheating is not allowed; the straightness is ≤0.10mm. The workpiece that has been straightened after tempering is re-tempered at 55°C xlh.

2) Effect. The slender aviation drill processed according to the above process has a hardness passing rate of 99% and a bending passing rate of 95%-98%.

After heat treatment, the roughly ground workpiece is returned to heat treatment to remove stress, which is beneficial to stabilizing the size of the aviation drill.