We know it works of course, due to the number of folks using it successfully. I however have been questioning lately if it really is the magical material everyone says it is.
Based on the information they are gracious enough to give us on their website, It is really not an appropriate choice for 4130 in this application.
They advertise a Rockwell Hardness of 20-24 C, whereas 4130 in the as-welded state will be a good bit less than that (something like 15-19, depending on a lot of things). Also the tensile strength is advertised as up to 120k! 4130 is more like 75-80 after welding. There’s no free lunch in metallurgy, so while they say it’s ‘crack desensitized’ (whatever that means), I have my doubts.
There’s also the case of the carbon from the 4130 mixing with it and potentially causing carbide precipitation with the advertised high chromium content.
I’m going to put on my tin-foil hat and wonder how many bike frames over the years have cracked because of this. I fully realize I’m going against the hive mind here, but it just doesn’t make sense with the information we’re given to use it at all.
And to really bang my head against the wall, it’s not even the best advertised choice on the Weldmold website! I just makes no sense other than the reputation of builders using it successfully. Some actual data sheets from them would solve all of this. Instead we have to rely on their marketing department.
Sorry if any of that sounds snarky, not my intention at all. I’m just genuinely puzzled how it became such a popular choice in the first place.