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Electric Resistance Welding (ERW)
Strip is unwound from coils and side-trimmed to control width and condition the edges for welding. The strip then passes through a series of contoured rolls which progressively cold-form it into a circular shape. The edges are forced together under pressure and welded by heating the steel to temperatures between 2200° F and 2600° F using copper contacts or coil induction.
Weld flash is removed from the the inside and outside surfaces of the newly-formed pipe, and the weld zone is heat treated to ensure homogeneity between the base metal and weld. The weld is subjected to in-line nondestructive testing, and the pipe then passes through a series of sizing rolls to attain its precise finished diameter. It is then straightened and cut to the desired finished length.
Butt (Continuous) Welding
The continuous process produces a full range of pipe sizes from only a few different widths of skelp. The coils of skelp, or strip, are fed into the mill and their ends welded together to provide a continuous flow. The strip passes through a pre-heater and into a furnace. The heated strip is shaped into an arc of about 270° in a forming stand before passing into the welding stand. There a nozzle applies oxygen to the edges to further heat them as they are pressed and welded together.
The pipe's OD and wall thickness are reduced in a stretch-reducing mill. Pipe is then cut to length, reduced to the required size in a sizing mill and water-cooled before being straightened. It is then ready for finishing operations.
Seamless
The production process for seamless pipe begins by heating a steel billet to about 2250° F. The red-hot billet is rotated and drawn by rolls over a piercing rod, or mandrel. The action of the rolls causes the metal to flow over and about the mandrel to create a hollow pipe shell. After reheating, the shell is moved forward over a support bar and is hot-rolled in several reducing/sizing stands to the desired wall thickness and diameter.
The pipe, which has grown significantly in length during the piercing and sizing processes, is then cut into sections and conveyed across a cooling bed to cool slowly in the air. It then receives whatever finishing processes are needed to meet customer requirements.
Cold Rolling
Changes in the structure and shape of steel achieved through rolling, hammering, or stretching the steel at a low temperature (often room temperature). This process creates a permanent increase in the hardness and strength of the steel.
The application of forces to the steel causes changes in the composition that enhance certain properties. In order for these improvements to be sustained, the temperature must be below a certain range, because the structural changes are eliminated by higher temperatures.
Hot Rolling
Product that is sold in its “as produced state” off the Hot Mill with no further reduction or processing steps aside from being pickled and oiled (if specified).
T6
Solution heat-treated and artificially aged to a stable condition. T6 is T4 that has been artificially aged.
 
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