Heat treatment of steel

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In the steel processing industry, it often occurs that heat treatment has to be carried out. Heat treatments of steel are often applied after production processes such as rolling, casting, welding and forming. These processes have a large and often disadvantageous effect on the structure and mechanical properties of the material. Industrial heat treatments consist of preheat and post-weld heat treatment. Delta Heat Services is an expert in heat treatment services on site. Also, Delta Heat Services has various stationary annealing furnaces at all its locations.

Preheat treatments

Preheating during the welding process is done to slow down the cooling rate of the material. By running this process in a controlled manner, it will reduce shrinkage and expansion of the heat affected area. This will minimize the chance of hydrogen cracking and it will improve the structure of the material. Preheat treatments are necessary to:

  • Prevention of curing phenomena;
  • Prevention of hydrogen initiated cracking (also known as cold cracking);
  • Prevention of binding errors; mainly used for welding thick aluminum and copper and for processes with low heat input;
  • Reduction of thermal stresses.

Post-weld annealing treatments

Post-weld heat treatments is done at the end of the welding process in order to improve the properties of the weld and the heat affected zone. During the welding process there is a very high temperature in the weld and the adjacent base material. Once cooled down, a thermal stress will occur. These voltages are reduced to an acceptable value with post-weld heat treatment. This also helps to reduce any increased hardness levels and improves toughness to an acceptable level.

Heat treatment methods

Heat treatments can be performed in several ways. At Delta Heat Services we offer electrical heat treatment, induction heating and annealing furnaces.

Electrical heat treatment

Electrical heat treatment is carried out through electric heating elements. The current encounters resistance in the elements, which will become hot and give heat off to the workpiece. This method of heating takes place during the preheating of welds as well as the local annealing of welds. The electrical heat treatment units of DHS are made for easy use and maximum mobility in the field. The 50kVA units are suitable for on-site and shop working and can control six individual thermocouples for preheat or post weld heat treatment.

Induction heating

Induction heating is mainly used for preheating activities on heavy construction works. This method of preheat is frequently used for heating up heavy materials. The induction cables can be placed in round coils for pipes or custom made shapes for construction work.

For moving items, Delta Heat Services offers the Rolling Inductor. This is a simple and cost-effective heating solution which delivers fast and consistent heat for pipes, plates and pressure vessels. The temperature is controlled by a thermocouple, which is specially designed to control and measure the temperature when the workpiece is moving.

Annealing furnaces

Delta Heat Services also performs heat treatments at its locations. Our stationary annealing furnaces can be used for a wide variety of heat treatment applications. The annealing furnaces are oil-fired or electrically heated. The furnaces vary in sizes which go up to a maximum of 18,5 meters. View this page for an up-to-date overview of the dimensions of our annealing furnaces.

On site service

Is the workpiece too big or too complex to transport to one of the fixed locations? Delta Heat Services has developed a mobile system so that annealing can also be carried out on location. The mobile system makes it possible to build a gas or oil-fired annealing furnace in any desired size in a very short period of time. The dimensions and possibilities are unlimited!

Would you like to know more about the different heat treatments of steel, our equipment or our services? Or do you want to request a quote or do you have another question? Please feel free to contact us without obligation.

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