( Div. of Sterling Tubes & Valves Pvt. Ltd. )

Cold Drawing & SRB / Honing Process Chart

Raw Material Seamless Mother Tubes

Mother Tubes has been purchased from Steel Mill ( Indigenous / Imported ) Drawing begins with procuring the raw material. Specified the material’s chemistry and dimensions including tolerances—size, wall thickness, concentricity, and straightness. In most cases, the annealed properties are specified for maximum softness. These requirements may be included in a proprietary specification or an ASTM, AMS, or MIL code or specification. First get it inspect at our ends for suitability of manufacturing process, after accepting by quality departments it moves for nest stage.

Pickling & Lubricating

Mother tubes are being pickle for removing rusting, abrasive scale (iron oxide) on the surface of the hot rolled rough stock and better outer surface, The surface of the tubes is coated with a drawing lubricant to aid cold drawing

Pointing / Punching Process

Several inches of the lead ends of the tubes are reduced in size by swaging or extruding so that it can pass freely through the drawing die. Note: This is done because the die opening is always smaller than the original tubes size. It require to drawing / sizing tubes

Cold Drawing & Sizing Process

In this process, the material being drawn is at room temperature (i.e. Cold-Drawn). The pointed/reduced end of the tubes, which is smaller than the die opening, is passed through the die where it enters a gripping device of the drawing machine. The drawing machine pulls or draws the remaining um-reduced section of the tubes through the die. The die reduces the cross section of the original tubes, shapes the profile of the product and increases the length of the original product.


Sinking is the term for drawing a tube with no internal support. It is usually performed as a sizing pass after a rod draw. The proper die angle depends on the D/t ratio; a properly chosen die angle minimizes the change in wall thickness. If the wall thickens too much, the ID surface finish will deteriorate.The bearing length is longer than with other operations, up to 50 percent of the die’s diameter, to ensure the roundness of the finished tube.Plug drawing and sinking can be used to draw a tube to a finished size

Heat Treatment & Stress Relieved Process

This is a annealing treatment generally used to soften the material being drawn, to modify the micro structure, the mechanical properties and the machining characteristics of the steel and/or to remove internal stresses in the product. Depending on the desired characteristics of the finished product, annealing may be used before, during (between passes) or after the cold drawing operation, depending on material requirements. After anneal treatment in high temperature, another anneal will be held in a lower temperature with longer dwell time. This step will use the same equipment but the difference is that all the stress of tube will be removed totally.

Alignment / Straightening

Straightening is usually performed using a six- or 10-roll rotary straightener (see Figure 5) with a combination of flex and pressure. While flex has little effect on properties, pressure tends to increase yield strength and raise the residual stress level. Exerting the minimal pressure is the best practice.

Hydro Testing

Hydrostatic (Hydro) Testing is a process where components such as piping systems, gas cylinders, boilers, and pressure vessels are tested for strength and leaks. Hydro tests are often required after shutdowns and repairs in order to validate that equipment will operate under desired conditions once returned to service.

Skiving Roller Burnishing & Honing

Skiving and roller burnishing is a two-part, one-pass process that removes stock with skiving knives, then cold-works metal surfaces with rollers to achieve the highest surface finish tolerances. This process is commonly used to finish hydraulic and pneumatic cylinders. Another is called honing. Honing is an operation that is used primarily to improve the surface finish of holes produced by processes such as boring, drilling, and internal grinding. The honing tool consists of a set of aluminum oxide or silicon-carbide bonded abrasive sticks, usually called stones.


Types Of Packing : Seaworthy Bundles (Hexagonal), Wooden Boxes, Crates (Steel/Wooden), Special Crates For U-Bend Tubes With Each Radius Baffles And Packing As Per Customer’s Requirements.

Extra Features : Each Bundle Covered With Plastic For Protection Against Extreme Weather. End Of Tubes Protected By Plastic Caps., Bundles Strapped With Plastic Strips., Each Radius Of U-Bend Tube Separated By A Separator., Packing List (Laminated) Placed With Box/Crate.

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