Welding(текст для второй подгруппы)

Welding.

1. Welding is the most important process to join metals. It is the only way to join two or more pieces of metal. Welding is widely used to manufacture or repair all products made of metal.

2. Welding is the best way to protect and conserve materials by protecting their surfaces with special metal overlays. Corrosion and wear of metals can be greatly reduced by welding.

3. There are many ways to make a weld and there are many different kinds of welds. There are approximately fifty different welding processes. They are subdivided into seven groups:

• solid state welding(SSW)

• arc welding (AW)

• brazing (B)

• soldering(S)

• resistance welding (RW)

• oxy fuel gas welding (OFW)

• welding processes

• other welding

4. The arc welding processes are defined as "a group of welding processes which produces coalescence of metals, by heating them with an electrical arc". The arc welding includes eight specific processes:

- the carbon arc welding (CAW) process;

- shielded metal arc welding (SMAW) process;

- submerged arc welding (SAW) process;

- gas tungsten arc welding (GTAW) process;

- plasma arc welding (PAW) process;

- gas metal arc welding (GMAW) process;

- flux-cored arc welding FCAW) process;

- stud are welding (SW) process.

5. Brazing (B) is " a group of welding processes which produces coalescence of materials by heating them to a suitable temperature and by using a filler metal having a liquidus above 840 ° F and below the solidus of the base materials. When the filler metal melts it slightly diffuses into the base metals thus holding the parts together".

6. Soldering (S) is " a group of joining processes which produces coalescence of materials by heating them to a suitable temperature and by using a filler metal having a liquidus not exceeding 840 ° F and below the solidus of the base materials". Soldering is divided into two classifications: soft and hard.

In soft soldering filler metals with low melting temperature are used while in hard soldering the melting temperature of filler metals is comparatively high.

7. Oxy Fuel Welding (OFW) is " a group of welding processes which produces coalescence by heating materials with an oxy fuel gas flame with or without the application of pressure and with or without the use of filler metal

8. Resistance Welding (RW) is" a group of welding processes which produces coalescence of materials with the heat obtained from resistance of the work to electric current".There are many types of resistance welding such as: spot welding, butt welding, electric arc welding.

9. Solid State Welding (SSW) is " a group of welding processes which produces coalescence at temperatures essentially below the melting point of the base materials being joined without the addition of filler metal. Pressure may or may not be used". Solid state welding includes: forge welding, cold welding, diffusion welding, explosion welding, friction welding, hot pressure welding and ultrasonic welding. These processes are all different and utilize different forms of energy for making welds.

10. Other welding processes include those which are not best defined under the other groupings. These are the following processes: electron beam welding, laser beam welding, thermit welding and other welding processes in addition to be etectrcoslag welding.