Presentation on theme: "Technology Education Dept. Bellwood-Antis High School Mr. Crowell Mr. Mackereth."— Presentation transcript:
Technology Education Dept. Bellwood-Antis High School Mr. Crowell Mr. Mackereth
WELDING - the heating of pieces of base metal to melt & fuse 2 pieces into a solid piece (also called FUSION WELDING.) Welding involves using a SIMILAR filler metal/rod to the pieces being welded. Example of WELDING: two steel pieces fused together with a steel rod is welding
BRAZING is also the heating of pieces of base metal to melt & fuse the two pieces into one solid piece. Unlike welding, BRAZING uses a NON- FERROUS filler metal with a lower melting point to the pieces being welded. Example of BRAZING: 2 steel pieces fused with a brass or bronze rod is BRAZING
All types of gas welding use OXYGEN to OXIDIZE (burn) a type of flammable gas. Although different welding fuels are used, the most common fuel, and the gas we will be using in this shop, is ACETYLENE. Welding with OXYGEN and ACETYLENE is called OXY-ACETYLENE WELDING.
Proper welding attire/equipment in our shop would include the following items: HAT w/ HAIR TIED UP LONG SLEEVES SOLID SHOES/BOOTS LONG PANTS #5 WELDING GOGGLES LEATHER WELDING COAT WEDLING GLOVES LEATHER WELDING APRON Basically, keep ALL of your skin and hair covered when welding!
The tanks, especially oxygen, are filled with highly compressed gases. IT IS EXTREMELY CRITICAL THAT ALL TANKS BE SECURELY CHAINED AT ALL TIMES! A tank with a cracked or broken valve becomes a deadly projectile or missile.
Check to make sure the regulators on the tank & the pressure regulators on the torch body ARE BOTH IN THE CLOSED POSITION. We then open the oxygen tank valve ALL THE WAY OPEN This prevents the valve stem on the tank valve from being bent by high pressure. We then open the ACETYLENE tank valve ONE QUARTER TURN. NO FURTHER! LEAVE THE TANK WRENCH ON THE ACETYLENE TANK VALVE. This allows us to shut the gas off quickly in the event of an emergency, such as a leak or fire.
We make sure that the gas and oxygen lines cannot be switched accidentally: OXYGEN hoses are GREEN, ACETYLENE are RED OXYGEN fittings have RIGHT hand threads. ACETYLENE fittings having LEFT hand threads. The ACETYLENE packing nut has a groove notched into IT. The OXYGEN packing nut has no groove. ALL Fittings must be tight. NO grease or petroleum products can be in threads! The torch body is equipped with either a welding tip or a cutting tip. Make sure to keep all tips clean.
The projects you are building will be made out of 3/32” steel welding rod. This steel rod is plated with a thin layer of copper to prevent rust from forming on the outside of the rod, or contaminating welds. The steel project pieces will be BRAZED together. The brazing rods used are 3/32” brazing rod with a coating of flux on the rod.
IMPORTANT: NEVER POINT A TORCH AT ANYONE OR ANY FLAMMABLE OBJECT WHEN LIGHTING THE TORCH. FIRST, set the regulators on the tanks to the desired amounts of pressure. (For our brazing, we will be using 5 lbs of oxygen and acetylene.) Once the correct pressures are set, open the ACETYLENE pressure valve on the torch body 1/4 turn, and then strike the spark lighter. LIGHT THE GAS WITH A SPARK LIGHTER! NEVER USE MATCHES / BUTANE LIGHTERS!
SSlowly add OXYGEN to the acetylene flame until a pale blue flame with an inner blue core appears. This is called a NEUTRAL FLAME. IIf too much acetylene is burned, a CARBURIZING FLAME will leave black deposits on the work. Slowly add oxygen to neutralize the flame. IIf too much oxygen is added to the acetylene, then an OXIDIZING FLAME will eat away at the filler rod and the base metal. Cut back on the oxygen. VVERY IMPORTANT! DDO NOT POINT A LIT TORCH AT ANYONE, DDO NOT LAY DOWN A LIT TORCH ON A TABLE!
FIRST, shut both pressure valves on the torch (acetylene first, then oxygen) SECOND, close the tank valves tightly (acetylene first, then oxygen) THIRD, drain both of the lines by opening the torch pressure valves. Do this until both pressure gauges on the tanks read ZERO. FINNALY, Shut the torch valves, and shut the regulators on the tank. TURN the screws out. (only done at the END of CLASS by instructor)