Weldability means many things to many people.
To us, "readily weldable" means that two pieces of steel, when welded by someone of average skillset, can be joined to create a proper weld with no signs of embrittlement or cracking. It means that the Heat Affected Zone is comparable to that of other high strength steels like armor. It also means that no preheating, post tempering, or special welding rod is required.
Flash Bainite 4140, 4130, 8620, 1020, 1010, and a dozen other alloys are readily weldable. There is a HAZ and the weld is only as strong as the welding rod one uses. The skill of the welder and the rod used has far more impact on the resulting joint than the very lean Flash Alloys tested.
Edison Welding Institute has welded Flash 4130 and the results are available from an AWS Presentation made by Ohio State University. A dozen other locations and fab shops have welded Flash Bainite with no signs of any concern at all. Three SAE Baja vehicles have been welded with Flash Bainite, one of which is on the 2nd from last page of the Power Point presention on this site.
Flash Bainite when welded does not eliminate HAZ. Our strongest weld to date is 129ksi from an ER120 weld rod. While this is only half the strength of 260ksi Flash 4130 parent material, it is still a very respectable strength. Considering that 6061-T6 aluminum is only 45ksi and the weld a little weaker, on a pound per pound basis, a Flash Bainite weld is still stronger than 6061-T6 aluminum or its weld seam.
In welded tubing, Flash Processing can be used to transform the tubing and the weld seam to Flash Bainite. Flash 4130 tubing is more than triple the strength of "chrome moly" 4130 tubing. The picture on the "company" page of this site shows the remarkable ductility of such tubing.
Two pieces of welded steel can also be Flash Processed. When welding raw AISI4130 with comparable chemistry filler rod, the resulting weld seam after Flash Processing can be just as strong as the parent material. In this case the HAZ is eliminated as the weld bead itself is Flash Processed.