ERW pipe

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ERW pipe
Lonrace uses the Electric Resistance Welding(ERW) process to obtain a continuous longitudinalseam weld on the tube it produces. This process depends on a number of important factors to ensure a complete weld. The most important of these factors are:
• Strip width size
• Strip preparation through the mill forming and finpass stand
• Induction of current in the strip and concentrationof the current and resulting heating of the steelalong the strip edges.
• Presentation of the strip edges at the tube mill weld stand
• Squeeze out of the resultant molten metal.
 
Strip Width Size 
Strip Preparation Welding Each size of tube produced has its own unique strip width.
The strip width is calculated using various parameters including, finished tube size, tube wall thickness,radius of corners desired (for square andrectangular tubing) and theoretical squeeze out ofmolten metal at the weld head. 
 
Lonrace purchases steel coils from primary mill sources and slits the coils to width on its own slitters in-house. The strip width is controlled to +/- 0.**0inches.

Weld treatment
An integral part of obtaining a sound weld is to ensure the strip edges are prepared properly prior to welding. This is accomplished by passing the strip, which is by this time partially formed into around section, through a series of rolls called fin passes. The fin passes are designed to burnish the strip edges to clean them for welding and to ensure the edges are beveled to the proper angle to allow the strip edges to come together evenly. The strip edges must meet in such a manner that there is no gap at the top (outside of the tube)or bottom (inside of the tube). This ensures an even amount of extrusion, or squeeze out at the weld head (sometimes referred to as weld pressure rolls)and without mismatch. Mismatch occurs when one strip is higher or lower than the other when the two edges meet. 

Cutting
After the molten metal is extruded out of the weld area it is cut from the outside and if required theinside of the tube to leave a smooth surface. A first off" the weld is inspected at each set up.The characteristics inspected are the amount of extrusion, the presentation of the strip edges,and complete bonding of the strip edges.

Specifications