In some welding procedures for specific metallic materials or certain thickness of the weld - we are required to heating before welding or heat treatment after welding. The process of pre-heat and post weld heat treatment is used to improve the quality of welds, eliminating the possibility of errors arising after welding. ITVC Global is specialized in providing professional services of pre-heat and post weld heat treatment for the welding process (PWHT & Preheat)

Our services:

-       Heat treatment of welded pipes, structures, tanks ... as required by the ASME, AWS, BS…

-       Material handling: carbon steel, alloy steel

-       Temperature handling up to 900^oC

The process of pre-heating before welding

 Joints before welding must be heated because of the following reasons:

-       Removing the steam out of the area will be welded. Heating temperature usually greater than the boiling temperature of water, removing water from the weld joint eliminates porosity, brittle, cracked of welds by hydrogen generated during the decomposition of water by high temperatures when welding.

-       Reduce the temperature difference between the heat source and the base metal. All arc welding process using heat welding are much larger than the temperature of the base metal. This difference causes serious problems such as rupture of the weld with high hardness metal and not meet requirement on mechanical properties of weld metal compared with base metal.

We can pre-heat the weld using natural gas combustion, electric heating, electricity or furnace. Heating process to ensure that the entire area of ​​welding was heated, heating the entire thickness of the weld metal.

Now day, the pre-heat machine is equipped with sensor systems, display & control the temperature help the heating work is controlled to ensure the quality of welding.

Post weld heat treatment process after welding

After welding, we need to do the post weld heat treatment for the following reasons:

-       Removal of residual stresses. Residual stresses after welding can cause brittle fracture, curve, deformation caused by welding.

-       For normalized steel or heated steel, the post weld heat treatment after welding help to balance the mechanical properties of different regions of the weld joint. Post weld heat treatment after welding ensures weld joint is equivalent to the strength of the base metal, as well as meet certain values ​​of impact strike.

-       For coarse grain structure of steel appearing in the electric welding process – it might have normalized after welding, the post weld heat treatment after welding will help to fine the grain structure, eliminating stress and hard variable regions affected by the heat.

-       For some hard alloys such as aluminum alloys - after welding, the post welds heat treatment method (homogenization annealing and aging organizations) to help restore the properties of metals as before welding.

Note: When performing the pre-heat, or post weld heat treatment after welding, the important is technician who perform the process must have well understanding of the technical requirements, the nature of the metal as well as the steps that would otherwise can cause serious effects on the quality of the product.

To request pre-heat and post weld heat treatment service - Please contact ITVC Global - you'll get useful advice and the best service.