The drawing metal forming a is mostly used to manufacturing of wire (small diameter metal rods than the bar) from the round bars, except instead of pressure from back end. The wire (wire drawing) is pulled from front side where it is emerges from circular die. It is effective method for producing the wire, based on cross sectional die required. Thus dies are made from hardened tool steels or tungsten carbine materials. Drawing and extrusion are may be hot (stock heated with high temperature) or cold (stock not heated).
The drawings have following process to make product.
- Wire drawing metal
- Tube drawing metal
- Hot drawing metal
Wire drawing metal:
The wire drawing set up is shown in figure. That process produce different diameter of wire is accomplished by pull a wire through die. It die is made from carbide. The larger diameter is cleaned washed, picked and lubricated for before starting of drawing process. When the cleaning process to remove any scale and rust presented on the work piece surface, which is affected by the die. That is normally cleaned by acid pickling. The hot rolled of steel is de- scaled, pickled with acid, washed through water and within lime and other type of lubrication. To provide easy entrance of wire into the die, the end of the stock is made pointed to facilitate the entry.
Pointed or reduce the diameter of wire at front duly lubricated and pushed to the die and cooled from water also. Rotary swaging or simple hammering is done at pointing. Then it pulled and gripped for attaching in to power driven reel, when the diameter of wire is reduced by reason of ductile property of materials through one set of die. For more reduction of wire diameter, various set of dies arranged in line.
The reduction of diameter in each pass through die range about 10% for steel and 40% for ductile material such as copper. The die used for wire drawing affected, because of high stresses induced and abrasion. The die material used in wire drawing such as tool steels, tungsten carbide, child cast-iron and diamond. The cast iron dies are used for small runs. The alloy steels are used for large size of wire drawing, For most commonly the Medium size carried out by using tungsten carbide die and also large production the tungsten carbide size are referred because of that is long life 2 to 3 time of alloy steel dies. For very fine wires require diamond dies are used.
The wire drawing metal improves the mechanical properties of material in the cold working. During the wire drawing the material loses its ductility property and repeatedly draw to bring it to the final size, for its ductility restored by using intermediate annealing.
The tubes are basically two types
- Seam less (without joint)
- With joint all long the length of tube.
The seamless tubes are made from rolling or extrusion process also.
For tube drawing method
- Rod drawing
- Floating plug drawing
- Fixed plug drawing
The tube drawing difference among the presence and absence of rod or plug, then how the plug is fixed position and die angle. Which the tube drawing sintered tungsten carbide die insert encased in steel. Where the cobalt content is 10% mixture in approximately high amount of cobalt content provide more shock resistance in the tubing metal. So lower of cobalt present in the metal provide better wear resistance.
It is a simple drawing of tube through a die to reduce the inside and outside diameters. The sinking method cannot be used in internal support. In sinking the wall- thickness dose not changed but it can be increase or decrease depends upon the die angle and diameter to wall thickness ratio. The wall thickness may be increased by internal diameter surface become rougher until sunburst cracking occurs.
The die angle is 24 degree and it has a relatively long bearing lower angle tend to cause the wall thickness. For higher angles cause wall thinning, the sinking use a long bearing to achieve the correct size and roughness, providing this process suitable for final require size of operation.
Sinking process cost is very low but advance application which cost is high, for multiple sinking operations completed after commodity tubing for application as low cost lawn furniture presented
2. Fixed plug drawing:
The fixed plug (or) stationary plug drawing is an oldest method for plug drawing of stainless steel. The smooth internal diameter surface can be provided in shortly with straight lengths. For slow operation become reduction limit together.
3. Floating plug drawing:
For stainless steel tube mostly suitable in floating plug proving. It is effective method to produce good surface quality tubing in continuous lengths more than 1000 feet. The tool is used by this method for critically compare than any other. Bearing must be long enough to permit the plug to seat in tube id, but the friction becomes a problem. The tool design, tube cleanness, lubrication are critical in floating plug drawing.
It is suitable for higher material yield than any other process and long- length capability.
The rod drawing draws the tube over hardened steel rod, or mandrel passed through die with tube. The rod drawing the die angle is 36 degree and short bearing length. It can be reduce outer diameter internal diameter and wall thickness.
That provide less friction and lower drawing force occurred than any other plug drawing operations, so that able to high reduction area than other methods. This advantages that provide two step operation (reeling and drawing).
The tube produces use of rod drawing the sizes is not suitable for plug drawing method such a heavy- wall thickness or small- internal diameter of tubing. It require low time operation so it suitable for small runs. The rod drawing method can be providing the rod the length of less than 100 feet.
The hot drawing methods pulling the metal through die for achieve a reducing in diameter. So the material to be drawn with diameter reduction.
As shown in figure the hot drawing method or shaping of metal where the heated blank is placed on the die and punch force applied in the blank through the die opening to form of cup or shell. When the drawing process multiple dies are used. By this process, the kitchen utensils and component of food processing are manufactured.