Arno Visser Posted July 1, 2012 Share Posted July 1, 2012 Hi everyone, After waiting what seemed like a year (in reality a few weeks), I finally had my long awaited class in pattern welding yesterday. Since there is only so much you can do in one day, we didn't have the time to make a big billet with so many layers, but still, I'm now the proud owner -and creator- of a nice piece of san mai. The first few hours of the day were spend on a theoretical part. For me this proved very useful. Still have some questions, but I'm getting to that part later. After that it was hammer time....We were told we were 'only' going to do a three layer billet. But we were given the most difficult weld to perform (according to the teacher). We were going to do a weld of iron to a 1,2% carbon steel. And he was going to make it easier for us by putting the iron plates on the outside. Since apparently iron heats up slower than this carbon steel. Anyway, the result is there. To a lot of you guys this may seem like nothing special, but this was mt first time..... I have taken some of the material from the side with a grinder and it seems like all went well. In the light you can see the color difference between the layers. I'm still thinking of what I'm going to make from this...... Now to my question. When I was in school to become a goldsmith, I had to learn a lot of theoretical things. Calculating the weight of the components you need to make a certain alloy (say, 18 carat yellow gold) was one of those things. So, I'm very into that stuff. What we were told was that making a billet is like creating a new metal. You have to think well. You need to have a clear picture of what you want to create and what you are going to use to create it with. Carbon migration and carbon loss are two things you have to think about, otherwise you might end up with a metal that has to less carbon to do a HT. Every welding cycle causes 0,03% of carbon loss. By the way....correct me when you think I'm wrong. I'm only repeating what I was taught. Also carbon migration causes a decrease in carbon. The example was like this. When you weld a piece of 1,2% C steel to a 0,3% piece, you'll end up with: (1,2+ 0,3)/2 = 0,75 and if you perform 5 welding cycles that leaves you with 0,75 - (0,03*5)= 0,6% carbon in your end product. Now, it's this first part that I have some questions about. I can understand that carbon migration causes one part to absorb the carbon of the other part. But I think that in this example the calculation is only correct when the two parts are equal in mass. When you take 1,2% C steel of 8mm thickness and 0,3% C of 4mm (the two pieces have the same length and width) , I don't think you'll end up with 0,75 (or 0,6 after 5 welding cycles). How does this work? Also, is my 0,3% piece after welding now suddenly 0,6% C throughout the whole piece or only in the zone closest to the fusion bond? Again, how does this work? Learning only raises more questions....... Arno Link to comment Share on other sites More sharing options...
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