Monday, 25 June 2018


Welding engineering covers  topics such as joint design, weld preparations and welding positions.Welding procedures are documents used by the welding engineer to guide the welder in the choice of consumable and welding conditions.They also carry other valuable information such as when preheating is required.
Many standards and classifications are used by the welding industry, but are they easy to understand? For example, MMA electrode manufactures and suppliers quote electrodes as being types E7018 but what does this mean? In fact, the numbers give an indication of the strength of the weld metal which will be deposited by the electrode and the type of coating the electrode has.When a weld is produced both the welding conditions used and the composition of the shielding gas can have a significant affect on the metallurgy.When welding stainless steels, carbon can be added to the weld metal through the decomposition of carbon dioxide used in the shielding gas.If too much carbon is added then this can affect the corrosion properties of the stainless steel.While calculating the welding cost following factors are considered :power consumed,consumable used,labor cost and gas cost.

Heat treatment

Heat treatment is often associated with increasing the strength of a material. There is a range of different heat treatments employed on materials before, during and after welding takes place.  Preheating is a method used to prevent hydrogen cracking taking place.  Heat treating a material can also be a method of reducing or removing stress which may have built up in a component either through forming or welding. It can be used to improve formability, restore ductility and to recover the grain size.It is usually done for  hardening,softening and property modification.Hardening heat treatment is suitable for steels.It is done for improving the  mechanical properties of steel.Sufficient carbon or alloy content is required for hardening.
Hardfacing involves one of two techniques: build-up or overlay. Based on the equipment needs, some may want to use a combination of both. The combination of the two techniques can be completed repeatedly provided that the part or equipment still remains sound.
The build-up technique  returns older equipment back to its original dimensions after it has been worn . The overlay technique adds a layer of protective filler metal deposits to protect against metal loss.
Hardfacing the teeth of digger buckets is carried out to improve the wear resistance of these components.Cladding of the internal surfaces of a vessel with stainless steel panels can mean that the structural parts of the vessel can be made out of a material which is cheaper, but the overall corrosion resistance and working life is not compromised.
Weld testing can be divided into two main areas; destructive and non-destructive testing methods.
In destructive testing, the sample of material or weld is snapped, broken and pulled apart by numerous techniques to gather data regarding the strength, toughness and hardness of the component.With non-destructive testing, as the name suggests, no physical damage occurs to the component.Techniques such as visual inspection, x-ray and ultrasonic testing are some of the most commonly used methods.
Welding and cutting defects:Welding and cutting defects do occur, even when care is taken to try and avoid them.  Understanding the main cause of these defects  is of fundamental importance in ensuring that the defects do not arise

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