Accidents frequently occur in welding operations, and in many instances, they result in serious injury to the welder or other personnel working in the immediate area. What many welders fail to realize is that accidents often occur NOT because of a lack of protective equipment, but because of carelessness, lack of knowledge, and the misuse of available equipment. You, the welder, should have a thorough KNOWL-EDGE of safety precautions relating to the job. But that is not all. You should also consider it a responsibility to carefully OBSERVE the applicable safety precautions. In welding, being careless can cause serious injury not only to yourself, but to others as well.

Bear in mind that safety precautions for the operation of welding equipment vary considerably because of the different types of equipment involved. Therefore, only general precautions on operating metal arc-welding equipment are given here. For specific instructions on the operation, maintenance, and care of individual equipment, use the equipment manu-facturers instruction manual as a guide.

In regard to general precautions, know your equipment and how to operate it. Use only approved welding equipment, and see that it is kept in good, clean condition. Before you start to work, make sure that the welding machine frame is grounded, that neither terminal of the welding generator is bonded to the frame, and that all electrical connections are securely made. The ground connection must be attached firmly to the work, not merely laid loosely upon it.

Keep welding cables dry and free of oil or grease Keep cables in good condition, and, at all times, take appropriate steps to protect them from damage. If it is necessary to carry cables some distance from the machines, run the cables overhead, if possible, and use adequate supporting devices.

When you use a portable machine, take care to see that the primary supply cable is laid separately so that it does not become entangled with the welding supply cable. Any portable equipment mounted on wheels should be securely blocked to prevent accidental movement during the welding operations.

When you stop work for any appreciable length of time, be SURE to de-energize the equipment. When not in use, the equipment should be completely disconnected from the source of power. Keep the work area neat and clean. Among other things, make it a practice to dispose of hot electrode stubs in a metal container. Proper eye protection is of the utmost importance, not only to the welding operator, but for other personnel in the vicinity of the welding operation. Eye protection is necessary because of the hazards posed by stray flashes, reflected glare, flying sparks, and globules of molten metal.

This following text covers the forms and principles of heat treatment in general. Both ferrous and nonferrous heat treatment of metals is covered. Informa-tion given is for training purposes only. When actually performing heat treatment tasks, you must refer to the applicable technical publications. Heat treatment is a series of operations involving the heating and cooling of a metal or alloy in the solid state for the purpose of obtaining certain desirable characteristics. The rate of heating and cooling determines the crystalline structure of the material. In general, both ferrous metals (metals with iron bases) and nonferrous metals, as well as their alloys, respond to some form of heat treatment. Almost all metals have a critical temperature at which the grain structurechanges. Successful heat treatment, therefore, depends largely on a knowledge of these temperatures as well as the time required to produce the desired change.