Welding Tips and Tricks

Can someone tell me about the finish on 4130 plate? I've been using .190" thick 4130 and the surface finish is a light mill scale brownish color. It's easy to buff off before I weld it. I recently bought plate from McMaster-Carr and its finish is much smoother more shiny grey color. I don't know where the plate I've been using came from, it was given to me. So my question is, was the plate I've been using possibly not 4130 or does .190" 4130 come with different finishes.

There is some 4130 tube coming manufactured in China; it's quite likely that plate could also originate from there.

In the days when 4130 was all manufactured in the US, there were often variations in surface finish depending on the manufacturer. The tube or plate usually had manufacturer identification.

Regardless of the origin, cleaning the area to be welded with a Scotchbrite disc always gave a cleaner weld.