Curved steel companies may receive the same requests for quotations, but their actual products may not be of the same quality.
When purchasing straight steel, you largely know what to expect. There are standardized specifications and tolerances that steel mills have to meet in order to certify it. Straight steel is essentially a commodity.
Curved steel, however, is a little different. Many applications are custom, and the tolerance requirements usually vary from job to job. Certain difficult jobs may be able to be done, but not to the same dimensional tolerance that an easier bending job would be. The quality you can expect largely depends on the shop that is making it. For easier bending jobs, the difference in quality may be negligible. When purchasing very specialized curved steel like stair stringers on circular staircases, going with an experience manufacturer who can provide a reliable part can often save your shop time and money as well as providing a better looking part.
Below is a picture of rolled plate for a stair stringer. As you can see on the upper portion of the staircase, there are 3 weld seams and each piece is no longer than 4′. This is a relatively easy staircase. (It’s a very slight radius, not difficult at all). It was obviously done by an inexperienced steel roller.
By way of contract, below you can see a picture of stair stringers we rolled from steel plate for Drexel University. This is a much more difficult staircase where Chicago Metal Rolled Products rolled longer segments at a much more difficult pitch and radius. As you can see, a much better looking staircase was the result.