HEAT TREATMENT (Pre-heat and Post Weld)

Pre–Heat Treatment (PHT)

This is the process whereby metal is heated to a pre-determined temperature before engaging in the welding process.

The purpose of preheat:-

• Reduce the risk of hydrogen cracking

• Reduce the hardness of the weld heat affected zone

• Reduce shrinkage stresses during cooling and improve the distribution of residual stresses.

NDTL provides this service by use of Heating consoles and thermal ceramic heating pads.

Post Weld Heat Treatment (PWHT)

 Post weld heat treatment (PWHT) is a term that refers to any heat treatment that is applied to a material after welding. The process is often used to improve the properties of the weldment. In most cases, the goal of PWHT is to increase the resistance of the material to brittle fracture by relaxing residual stresses which can occur in welds due to restraint by the parent metal during weld solidification. When these residual stresses combine with normal load stresses it is possible that they may exceed the material's design stresses which can cause weld failure.

PWHT can also be used for hardness reduction and material strength enhancements among other things. The extent of relaxation of the residual stresses depends on the material type and composition, the temperature of PWHT and the soaking time at that temperature.

 NDTL provides certified personnel and equipment for both Pre-heat and Post weld heat treatment services.

BRINELL HARDNESS TESTING (BH)

This method of testing is used to examine and assess the integrity of the surface of metals by measuring the resistance to deformation. The term hardness may also refer to resistance by bending, scratching, abrasion or cutting. This procedure is used to determine the hardness of a material by accurately measuring the diameter of an indentation made on the surface by using a Brinell Hardness test machine applying a specific force and measuring the resultant indentation.

NDTL provides portable and easy to use Brinell Hardness test equipment for general industry applications.