Induction Annealing Brass Bullet Shells Heating Treatment UHF Series With Induction Heating System

Application Note Objective:

A manufacturer of brass bullet shells wants to upgrade their existing induction heating equipment and is looking for improved efficiency. The goal of this application test is to demonstrate that the DW-UHF-6KW-III induction system will meet and exceed its requirements for achieving improved heating times and maintaining heat uniformity within the targeted area. Two sizes of brass ammunition shells were used for the test – bullet casings with 1.682” (42.7 mm) length and 0.929” (23.5 mm) length. The targeted annealing time is 0.6 seconds for both parts using a single induction heating coil.

Equipment: 

HLQ  DW-UHF-6kW-III air-cooled induction heating system was utilized in the annealing process. Tempilaq paint was used to determine if the desired temperature in the annealed area is reached.

Process:

The brass bullet shells were positioned in the induction heating coil. The area to be annealed took about 60% of the part’s length counting from the open end. The heated area was painted with Tempilaq which helped us evaluate the temperature distribution. Both parts successfully reached the target temperature of 750°F (398°C) in 0.6sec. For the smaller part, the power supply power was reduced to 45% to prevent the part’s overheating.

Induction Annealing

In general, the main purpose of induction annealing heat treatment is to soften the steel, regenerate overheated steel structures or just remove internal tensions.

It basically consists of heating to austenitizing temperature (800ºC and 950ºC depending on the type of steel), followed by slow cooling.

Induction Annealing is a heat treatment process which involves heating of material above its recrystallization temperature. The aim is to reach and maintain a suitable temperature for enough time followed by proper cooling. It is often used in metallurgy and material science to make the treated sample more workable by reducing its hardness and increasing its ductility (ability to undergo a change of form without breaking).

Annealing alters the physical and sometimes the chemical properties of the material as recrystallization is obtained during the process of cooling. Therefore, the outcoming structures of many alloys, including carbon steel, are both dependent on the heating and on the cooling rate. Ferrous metals, such as steel, require slow cooling to anneal. Other materials (e.g. copper, silver) can be either cooled slowly in air or quickly quenched in water.

Induction heating provides improved control of the annealing process. Repeatable heating profiles can easily be obtained by precise regulation of the heating power. Since the workpiece is directly heated by the magnetic field, a faster response can be achieved. Moreover, the high overall efficiency of the induction heating process is crucial for such lengthy treatment.

Compared to most of the standard methods, induction annealing is a clean and easy to automate, contactless approach providing a high quality of the treated workpieces.

Induction annealing heating advantages:

Processed in line with control of parameters in real time
Metallurgical results similar to those obtained in conventional ovens
Less environmental pollution
Increase energy efficiency
Reduced processing time
Ability to control the heat, temperature accuracy
Ability to heat small areas without changing the characteristics of the rest of the part
Cycle accurate and repetitive heat
Reduction of surface oxidation
Improved job environment

Some related industries are tube and pipe, medicine, oil and gas and automotive.