overheating steel

overheating steel

Hazards and Preventive Measures of Overheating Steel Materials in Crane Wheels

When the heating temperature of steel exceeds a certain temperature, or the steel is kept at high temperature for too long, the austenite grains in the internal structure will become sharply coarsened, which is called overheating. The overheating of steel is affected by two factors: heating temperature and holding time. Among them, the heating temperature has a greater impact on the coarseness of austenite grains: the higher the temperature, the more serious it is that large grains will engulf small grains with the same orientation, so the larger the grains will be. Usually, the temperature at which grains begin to grow rapidly when steel is heated is called the critical temperature for grain growth. Use it as the upper limit for controlling the initial forging temperature. If it exceeds this temperature, the steel is considered to be overheated.

The dangers of overheating steel:

1. Severely overheated steel may have cracks in its corners during forging.

2. Generally overheated steel does not affect forging, but the grain size of forgings made from overheated steel is still larger than that of normal forgings, which reduces the impact toughness, plasticity, strength and other mechanical properties of the crane wheel.

3. Forgings made from overheated steel forgings may easily cause deformation and cracking during heat treatment and quenching.

Preventive measures for steel overheating

1. Strictly control the heating temperature and holding time of steel materials to prevent overheating

2. Some of the overheating of steel can be eliminated by heat treatment (normalizing or quenching and tempering) to refine the grains, and some can be eliminated by repeated forging methods to improve the overheated structure.

3. For steel types without phase transformation such as chromium-nickel austenitic steel, heat treatment cannot be used to change the overheated structure. Measures should be taken to prevent overheating.

Before determining the basic principles and basic methods of the forging temperature range of wheel forgings, you should first know what is the forging temperature range? The temperature at which forging begins is called the initial forging temperature. The lowest temperature at which forging is stopped is called the final forging temperature. The temperature range between the initial forging temperature and the final forging temperature is called the forging temperature range.

The basic principles for determining the forging temperature range are:

1. Make wheel forgings have better plasticity and lower deformation resistance within the forging temperature range.

2. Ensure to obtain high-quality wheel forgings whose internal structure and mechanical properties meet the technical requirements.

3. Expand the forging temperature range as much as possible to reduce the number of fires, save energy, and improve forging productivity.

The basic method of determining the forging temperature range is

1. Carbon steel can be directly determined according to the iron-carbon alloy status diagram

2. Alloy structural steel can generally be determined by referring to carbon steel with the same carbon content

For high-alloy steels and superalloys with low plasticity, as well as steels that do not undergo phase change (such as austenitic steel and ferritic steel), equilibrium diagrams, plasticity diagrams, resistance diagrams and recrystallization diagrams are determined by comprehensive analysis of three aspects: plasticity, quality and deformation resistance.