DEFINITION OF WELDING
“Welding is the fabrication process which involves the metallurgical fusion“. Here, interface of two parts joined are brought to temperature above the melting point and the allowed to solidified so that the permanent joining takes place.because of permanent nature of joint and strength being equal to or sometimes greater than that of parent metal makes welding one of most intensively used method. Various welding joint are using in welding process like butt joint, lap joint,edge joint, tee joint etc.
TYPES OF WELDING JOINT
Different types of welding joint are classified as:
- Butt joint
- Lap joint
- Corner joint
- Tees joint
- Edge joint
Each of above joints can have any of four different welding position like Flat,Horizontal, Vertical and Overhead.
BUTT JOINT: In butt welding joint both parts lies in same plane and weld their edge.
LAP JOINT: Lap joint welding of both parts are overlap.
CORNER JOINT: In corner joint of corner joint of right angle or joint center of the angle.
TEE JOINT: Tee joint welding one joint is right angle to the respective joint. it is in ‘ T ‘ shape.
EDGE JOINT: Edge joint of are parallel with one of another edge and making edge joint.
IMPORTANT FACTOR BEFORE ANY WELDING JOINT:
We now discuss about some important point before of any welding joint in welding process.
- By virtue of metal being melted at the interface in a welded joint it is necessary that the interface are very clean. if the interface are with any oil,dirt, or grease left,then these would interface with proper fusing of the metal and thus weaken the joint. it is necessary that joint surface are thoroughly before the welding is started.
- Remove the oil substance from the surface, the organic solvent like acetone and carbon tetra chloride may remove means of cleaning with a rag socked in the solvent. the heavier oxide film removed by acid picking wire brushing or emery.
- The oxide present on the surface would also interface with proper fusing hence they are eliminated by the use of fluxes.
A flux is a “material use to prevent, dissolve, or facilitate removal of oxide and other endorsable surface substance” as defined by American welding society.
The flux is expected to react with the oxides present and from low density slag which would float on top of the molten metal pool protecting it from further oxidation. the types of fluxes used depends on The operation and the parent metal that is being welded.
REQUIREMENT OF WELDING
- In welding, requirement of welding is a filler metal. expected for the resistance process, all the other processes require a filler metal to fill the gap between the parts to be joined.
ideally the composition of the filler metal would be same as that of base metals which are being join for proper mixing with base metal.
- Another criterion used for a classification of the joining processes is based on the composition of the joint. According to this scheme, all joining processes grouped into three joining process:
- In the Autogenous process no filler material is add during joining . All type of solid phase welding and resistance welding are example of Autogenous.
- Homogeneous joining process , filler material use to provide the joint is the same as parent material. Arc, gas, and termite welding is belong to this category.
- In the heterogeneous process a filler material different from the parent material is use. soldering and brazing are two such joining process.
When two materials which are insoluble in each other , like iron and silver can join by a heterogeneous process.
this achieve using filler material(copper and tin) which is soluble in both the parent materials(iron and silver).