Cold Drawn Process:
A draw that is successful is result of five steps distinct:
1. The procurement of raw materials
2. Drawing it out in preparation to draw
3. Drawing
4. Straightening
5. Final inspection and closing
The tubing used for redrawing is either seamless or welded. Redrawing the process for both is basically the same, consequently, the processes that are described in this article can be applied to both.
Welded tubing is created from strips that have been rolled, cut and then coil-rolled. When the coil is taken to the facility that produces tubes then it is uncoiled before being is fed into a mill which transforms it into a tube shape. The resultant seam is then welded. Low-alloy and carbon steels generally are welded using electric resistance ( ERW) and the stainless steels can be Gas Tungsten Arc Welded (GTAW).
1.Procurement
Drawing begins by obtaining an initial raw materials. The purchase order should include the chemical composition and dimensions of the material including tolerances, wall thickness, size as well as concentricity and straightness. In the majority of cases, properties of the annealed material are listed to provide the highest degree of softness. These specifications could be found in a specific specification that is proprietary or in an ASTM, AMS, or MIL code or specifications.
2. Pointing
Following that is to point and is the process to reduce the diameter by a couple of inches of tube’s end to allow it to be drawn by the drawing die. The three most popular methods for pointing are push-pointing or rotary swaging. They also squeeze point. In some instances the coating of phosphate (also known as soap film) is used prior to drawing.
3. Drawing
Draw benches are generally mechanical, and consist of three parts that include a back bench die head and a front section. Jaws on a trolley grasp the tube, and an attached hook on the rear of the trolley is connected to the chain in a move, pulling the tube through an die. Dies are usually made of tungsten carbide sintered with an cobalt binder which are shaved-fit into an aluminum casing.
Tubes are drawn to a final size by using one or more of the following methods:
- Plug drawing, which includes floating, fixed as well as semi-floating (tethered)
- Sinking
- Rod or Mandrel Drawing
-Rod Drawing: During rod drawing the mandrel of a hardened steel is put in the bores of the tube into which it is directed. Once the tube has been put into the die the oil that lubricates it is pumped onto the tube’s surface, the jaws of the trolley grip the rod or tube tip and the trolley hook is inserted into with the chain and then the tube is drawn into the die. Die diameter determines the OD, while the rod’s diameter is the determining factor for ID. A well-chosen die will minimize changes in the wall’s thickness prior to the tube contacting the mandrel.
-Plug Drawing: Two types of plug drawing are floating and fixed. Fix plug drawing is made using an unfinished rod that is anchored to the rear on the bench. A lubricant flows through the rod until it reaches an opening at the front of the rod, allowing the lubricant to get into the inside of the tube’s ID. An angular tungsten carbonide plug is brazed or threaded onto the rod’s end and the tube is then positioned onto the rod, with lubricant is pumped over the OD surface, and then the tube is then drawn.
One of the advantages of drawing with a fixed plug is the fact that it creates an even ID. Another benefit is the fact that the taper permits to alter the ID to ensure a precise tolerance. Although it only requires one person to operate it however, the speed of drawing is not very fast, and the area reductions can be quite small, about 25% in stainless steel.
-Sinking: is the term used for drawing a tube that has no internal support. It is typically performed as a sizing step following the rod draw. The ideal die angle is based on the ratio D/T; an appropriately chosen angle will minimize the variation in wall thickness. If the wall is thickened excessively it will cause the ID surface finish will degrade.
The concept of lubrication is a further important aspect to consider alongside drawing schedule and tooling.
4. Straightening
Straightening is generally done with an ten or six-roll straightener that rotary uses an assemblage of pressure and flex. While flex does not have any effect on the properties of the product however pressure can increase the yield strength and raise the level of residual stress. Utilizing the least pressure is the ideal method.
5. Finishing
Finalizing operations can include polishing, pickingling or sandblasting to enhance the appearance of the surface as well as remove tiny imperfections. The final inspection procedures will be determined by the client’ requirements for the order.
We are in Meta Engitech, manufacture top-quality CDW tube with extraordinary dimensions for the surface and various OD & tolerances. We use international standards of quality to ensure that we offer the finest quality products to our clients. We employ the value-analysis and value-engineering method to increase the value of the products we create in order to be the most reliable manufacturer of tubes. We are in close contact with our clients and modify these tubes to meet the specifications of their customers.