Flame heating surface quenching use and precautions

Preparation before quenching

1. The workpiece shall be prepared for heat treatment by tempering and normalizing

2. The workpiece surface is not allowed to have oxidation skin, dirt, oil, etc

3. The workpiece with serious decarbonization, crack, sand hole and porosity on the surface cannot be quenched by flame

Preparation before quenching

1. The workpiece shall be prepared for heat treatment by tempering and normalizing

2. The workpiece surface is not allowed to have oxidation skin, dirt, oil, etc

3. The workpiece with serious decarburization, crack, sand hole and porosity on the surface shall not be quenched by flame

Flame preheating

Cast steel, cast iron, alloy steel parts can be quenched nozzle with a small flame to slowly heat the workpiece to 300~500? C around to prevent cracking.

The quenching temperature of steel parts is Ac3+(80~100? C) the quenching temperature of cast iron is 730? C + 28 x omega Si? C - x 25 Mn omega? C.

Flame intensity:

1. Common gas to acetylene and oxygen, acetylene and oxidation ratio to 1:1.5 ~ 1:1.25zui.

2. Oxygen pressure to 0.2~ 0.5mpa, acetylene pressure to 0.003~ 0.007mpa (buoy acetylene generator pressure to 0.006mpa), the normal flame is blue neutral to give.

3. The operating pressure of gas is 0.003mpa, and the strength of propane gas is 0.005~ 0.01mpa.

Distance between the flame and the workpiece:

1. Shaft workpiece usually give 8~15mm, large take lower limit near, complex shape small take upper limit far.

2. When the gear whose modulus is less than 8 is heated and quenched at the same time, the distance between the flame core of the nozzle and the tooth top is 18mm is preferred, and the circular linear speed of the gear is <6m/min.

3. When the single tooth of the gear is quenched successively, the distance of the flame core from the tooth surface is 2~4mm.

Nozzle or workpiece moving speed:

1. Rotation method: the linear velocity is 50~200mm/min

2. Propulsion method: the linear velocity is 100~180mm/min

Distance between the flame center and the water jet hole:

1. Continuous quenching: 10~20mm, too close, water easy to splash fire. Too far, insufficient or too deep hardened layer.

2. The spout should be tilted back 10? ~ 30? There should be a partition between the water jet hole and the fire hole.

Quenching medium:

1. Tap water pressure is between 200 and 300kPa.

2. Alloy steel 30~40? C, 1.5-2h, large pieces can be self-tempered (cold to 300? C).