SEAMLESS MANUFACTURING PROCESSES

Hot Finished

Prior to extrusion, a short round billet is pierced or bored to form a hollow billet. The billet is then heated and a mandrel is pushed through. The mandrel is then concentrically positioned to a circular die. Elongation Is carried out by squeezing the billet through the annular space formed by the die and the mandrel. Elongation of the material then takes place to attain the required dimensions. 

Cold Finished

Stainless steel pipe and tube made by the hot finishing process may have some limitations which might create the need for further cold finishing operations. Cold finishing is desirable to achieve:

(i) closer tolerances of material,
(ii) cleaner and smoother surfaces,
(iii) more readily controlled mechanical properties,
(iv) a far greater range of sizes, particularly small diameters and thin wall thicknesses,
(v) an almost limitless range of non-circular shapes.

Cold finishing is obtained by drawing a tube with larger outside diameter and wall thickness than the finished product through an external sizing die. The Internal size can be controlled by the use of a plug or mandrel.

Centrifugal Cast

The cast tube or pipe is formed by centrifugal force generated as the metal becomes entrained on the inside of a spinning cylindrical metal mould. This gives a tubular casting with the outside diameter and length determined by the mould size and the inside diameter determined by the amount of metal poured. Centrifugal cast materials come in a range of sizes and these are generally limited to a minimum of 65 mm OD and a maximum of 650 mm OD. Lengths to 5 metres are available although 2-4 metres is more common.

Forged and Bored

An ingot or bloom is forged and brought as nearly as practicable to the finished size and shape by hot working. The material is adequately worked under a tool of sufficient capacity to refine the structure in the wall of the finished pipe. After heat treatment the inside and outside diameters are machined to final size.

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