Welding with gas made by burning fuel gas mixed with oxygen (O2), giving rise to a high temperature flame (3000o) were Able to melt the parent metal and filler metal. Type of fuel used acetylene gas, propane or hydrogen, so the way this welding oxy-acetylene welding is called or known by the name of the carbide weld. Acetylene flame is obtained from burning a mixture of oxygen and acetylene gas used to heat the metal until it Reaches the melting point of the parent metal. Welding can be performed with or without filler metal. Oxygen is obtained from electrolysis of water or liquefaction process. Oxygen is commercially Generally come from the air liquefaction process in the which oxygen is separated from the nitrogen. Oxygen is stored in steel cylinders at a pressure of 14 MPa. Acetylene gas (C2H2) is produced from the reaction of calcium carbide with water. Rising gas bubbles and sediment That Occurs is calcium oxide. Reactions occur in acetylene cylinder That is:
CaC2 + 2H2O ® Ca (OH) 2 + C2H2
calcium carbide acetylene gas Cretaceous shallow water
When the count was approximately 1 kg CaC2 Produce 300 liters of acetylene. The nature of acetylene (C2H2) the which is a fuel gas is colorless, non-toxic, odorless, lighter than water, growing niche to separate Themselves when there is an increase of pressure and in temperature (above 1.5 bar and 350 ° C), soluble in a porous mass (acetone).
Calcium carbide is a hard, like stone, gray and formed as a result of Reaction Between Calcium and coal in electric kitchen. The reaction is then crushed, selected and stored in a sealed steel drums. Acetylene gas can be obtained from the acetylene generator acetylene gas produced by mixing carbide with water or can now be purchased in the gas tubes ready for use. To be safe acetylene gas pressure in the tube should not exceed 100 kPa, and kept mixed with acetone. Acetylene tube filled with a porous filler material is saturated with acetone, then filled with acetylene gas. Tubes of this type can accommodate acetylene gas pressurized to 1.7 MPa.
Principle of welding is not too complicated. Simply by adjusting the amount of acetylene gas and oxygen, then ends with a flame near the flame Brought Will Arise. But the amount of acetylene gas and oxygen should be arranged so as to turn the pressure bit by bit. Acetylene gas when it is turned on the flame of the flame used to remove soot. If the acetylene gas too little is played, then the weld will not light.
Speed of recall of gas per hour from an acetylene cylinder must not be Greater than 20% (one fifth) of its contents, so That gas can be flowed acetone (acetylene cylinders must always be perpendicular).
Flame combustion in oxy-acetylene welding may change depending on the ratio Between oxygen gas and the gas asetilennya. There are three Kinds of fire in the oxy-acetylene welding as shown in the figure below:
More acetylene flame (flame carburizing)
That if too many comparisons used the acetylene gas in the inner cone and outer cone will Arise a new cone of blue flame. Among the light cone and the outer sheath of the cone will have whitish, Whose length is determined by the amount of excess acetylene. This will cause the liquid metal carburizing. Flash is Widely used in metal welding monel, nickel, Various types of steel and a variety of non-ferrous material surface hardening.
That if too many comparisons used the acetylene gas in the inner cone and outer cone will Arise a new cone of blue flame. Among the light cone and the outer sheath of the cone will have whitish, Whose length is determined by the amount of excess acetylene. This will cause the liquid metal carburizing. Flash is Widely used in metal welding monel, nickel, Various types of steel and a variety of non-ferrous material surface hardening.
Neutral flame
This Occurs when the flame of oxygen and acetylene ratio of about one. Flame consists of a cone in a shining white and blue cone outer nodes. Required oxygen flame comes from the water. The maximum temperatures as high as 3300 to 3500 ° C is reached at the end of the flame cone.
More oxygen flame (flame oxidation)
When oxygen gas is more than is needed to Produce the neutral flame flame Becomes shorter and the color changed to purple cone. This flame will cause oxidation or decarburization process on the liquid metal. This oxidation is the flame That must be used in fusion welding of brass and bronze, but not recommended for other welding.
Because it is Able to change the composition of the molten metal excess acetylene flame and the flame of oxygen excess can not be used to weld steel. At the end of the temperature of the cone in approximately 3000 ° C and in the middle of the cone is approximately 2500 ° C.
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