First heat treat... If u wanna call it that

[66mynd]

Ok so I had my first experience with heat treating today at work. I've been reading alot of posts here at this site as well as researching as much as I can on knife making, heat treating, and I just got a book on basic metalurgy. Anyway, I'm an ironworker and I'm working on a bridge bustin rivets. We got this thing called a helldog and its almost identical to a jackhammer. It runs on 120 psi and you first put a chisel in it and hold it on the rivet head and press the lever. It shears the head off the rivet after a while. Then you put a different tip with punch and it pushes the rivet out of the hole (if your lucky). Anyway on the chisel tips we've been using you could see that it was machined because of the small grooves that the machine made while making it. These chisels could cut off 30 to 50 rivet heads before it would break off. We then got these new chisels. After cutting between 2 and 5 rivets it would warp and bend the tip. So I looked at the chisel and it looked like it was casted. Then I taped the cast chisel and then tapped the machined chisel, the cast would ring lower. So I took a cast chisel and heated the end (about 2" from the tip) till it was glowing orange to almost yellow. Then like an idiot I dipped in in a plastic container of oil (remember my first time) So I got about 15 seconds of quench before the container melted. Ultimately I could touch it with my bare hand after about 20 min. From what I read the past couple days... correct me if I'm wrong, but I think I normalized it because it basically cooled at room temperature. So after I tried it, the chisel tip bent on the first rivet. Which would make sense because doesnt normalizing reduce the hardness of the steel? Anyway I'm probably sounding very uneducated mainly because I am. I'm curious to know the difference in steel between the two chisels. I figured I'd throw this out there and get proffessional insight. My questions are... would having a tool that is casted over machined make a difference? What if its the same type of steel? If the one chisel looked like it was casted does that mean that it was just poured into a mold or pressed while still hot? And if I wanted to heat treat the cast chisel with a torch and a can of oil or water would it be possible? And lastly I was wondering what type of steel this type of tool would be made of and how that comes into play. Thanks if you read this whole mess but I gotta learn this stuff somehow. Thanks again -Ray

 

[mete]

"what type of steel" , well that's what we call "mystery steel" meaning it could be any one of many different types. Without knowing what type it's hard to know how to heat treat it. That type of tool used to be made usually of S5 or S7 a silicon shock resisting steel.

 

[66mynd]

Well just say that its an S7. Can they pour that into a mold to make a cast tool out of S7, and would it be any better or worse than if it was machined into the same part?

 

[K Williams]

Ha ha! I'll never forget the first time I tried to bust rivets! The punch was hitting everything except the rivet. Local 40 ironworker here. What Local are you out of?