Heavy Metal, Part 5 - Cold Rolled vs Hot Rolled Steel

Addressing cold rolled steel versus hot rolled steel

There is a difference in dimensional accuracy between cold rolled and hot rolled steel. That should be made especially clear at this point. Generally, you can trust the dimensions of cold rolled steel but it should always be checked especially, if precision is important. Hot rolled steel is not guaranteed to be dead-on accurate due to mill scale it has and the way it is processed at the mill. If you are working on a project employing a lot of TIG welding of aluminum , keep in mind that most aluminum is accurate dimensionally but it never hurts to check. Making sure that your metal is dimensionally accurate before starting a welding project is not the only challenge you’ll face in material selection. Warps, bends, twists and even cracks are often present, especially in imported metal. Tubing and pipe will sometimes have cracks running longitudinally down the length next to the welded seam. Structurally this can be devastating and if it is pipe that is to carry liquid, this is a inexcusable defect. This metal would often be culled at the mills, but when dealing with a competitive price market, it can slip through in individual pieces or whole bundles. Personally, I’ve seen whole loads where this was the issue. The same is true for loads of tubing that was warped. It will often be packed in the center of a bundle to hold it straight so the buyers do not notice and when it is de-banded, the pieces show their true nature. However, if caught by the end customer before it is loaded or delivered, a bargain price can often be struck for this with the supplier if the end customer thinks it can be used in non-critical areas or can salvage the good areas. Often it will be shelved for sale with the rest at the supplier, with employees not taking note to report, pull or return the metal. In handling at the supplier, many times metal is improperly stored or damaged in handling. Improperly supporting long lengths of metal at the metal supplier whether it’s tubing, angle, channel or beams, will soon impart permanent bows, bends, and other forms of warping. Often times defects are difficult to see until it is too late…some of which can be quite dangerous let alone very costly to repair. It’s always best policy to carefully inspect the metal stock you are using before taking your MIG welder or Stick welder and zipping it together.

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