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Arc welding: Heat generated by electrons jumping an air gap Causes the base metal and electrode to melt. Shielded Metal Arc Welding: SMAW Uses flux covered electrodes or “sticks” to add filler metal to The welding process. The flux is a special coating that burns while the electrode Is melting. This smoke keeps the atmosphere away from The molten metal. This type of welding is fairly inexpensive and most people Can have some type of mastery. SMAW works well on rusty metal. Arc welders: Produce a temperature of about 9,000 degrees F Usually range from 20 –225 amperage output. Duty cycle – refers to the number of minutes out of ten minutes The welder can be operated continuously without the amperage Output dropping. Welding current produced: Electricity or current is simply the flow of electrons. There are two Basic types of electricity, Alternating current and Direct current Direct Current: (DC) The electrons flow only in one direction. Polarity: The direction in which the electrons flow in DC current. 60% of the heat in an electric arc is generated on the positive Side of the air arc. Straight: In Straight (DC-)polarity the Electrode is Negative (SEN) The base metal is positive, deep penetration in it Reverse: In Reverse (DC+) polarity the Electrode is Positive (REP) The base metal is negative, shallow penetration Alternating Current: (AC) Electrons flow back and forth. Polarity: There is no actual polarity that can be set in AC welding. Because the electrons flow back and forth the current is made Us of 50% DC- and 50% DC+ Some welding machines are capable of producing both AC and DC Welding current. Welding cables: Large diameter copper wire with a rubber coating They are large so there is very little voltage drop for current flow, And so they are a better ground than you are. Ground Clamp: Electrode holder: Attaches to the base metal to provide a complete Circuit for the welding machine Holds the stick, it has grooves made in it to hold The electrode in different positions. It also helps complete the welding circuit Sometimes called the “stinger” Welding electrodes: The production of quality electrodes was the key to commercial arc Welding. The first electrodes were metal rods with string wrapped around it Rolled in flour. As the flour burned it pushed the atmosphere away. By the 1930’s good electrodes were being produced Before arc welding light metal was oxy-fuel gas welded and heavy Metal was riveted. There are many types of electrodes available today how can we tell The difference between them? National electrical Manufacturers Association (NEMA) color code A color coding system that identifies electrodes by colored dots on The end, base surface, and flux coating. Most manufactures use the number coding system as well as the NEMA system as it is easier for most people to understand. American Welding Society (AWS) numerical code. The most popular guide to selecting electrodes. Electrodes are given numbers that correspond to their tensile strength, Welding position, and type of current setting or penetration. AWS welding rod code: