I was an electrician at an integrated steel mill until 1991 when it closed in bankruptcy Ch.7. The entire steel industry had been enduring tough times for over a decade before we closed. Because of this turmoil, I was bounced around to every department from Blast Furnace to where it was shipped out the door. A few times, I was "bumped" from the Electric Dept. and worked for short periods in various production jobs. I viewed this as an opportunity to learn and see every aspect of the operation and felt lucky in a way that I was not like the older guys who spent 30 or 40 years in one department. Steel making is fascinating, but hot, dirty, and dangerous. I got to see it all.
I am here to tell you that thanks to inspection, quality control, and metallurgical testing, a percentage of product was scrapped at every stage of the game. Typically, in the Melt Shops, i.e. the Blast Furnace, Electric Furnace, or Basic Oxygen Furnace, testing was done and samples sent to the Met. Lab during the heat and the "recipe" could be adjusted until the alloy met customer specifications.
Once it was poured into ingot molds and subsequently hot rolled into slabs and strip, little could be done except to scrap and remelt what was bad. A very common problem was "rolled-in scale". Sometimes this was detected in slabs which were scarfed. Scarfers, wearing wooden soles on their boots and long underwear even in the summer, inspected hot slabs and scarfed out cracks and visible inclusions with a large torch and filled them with scarfing rod which was all the same, no matter what alloy slab was thusly fixed. Sometimes inclusions would be visible on the surface of finished product after rolling and pickling, and this would be rejected if it was caught. X-ray inspection would sometimes break down and human inspectors are not perfect either as we all know.
Long story short: sometimes bad steel made it to the customer. Sometimes the customer would catch it during their manufacturing process and they would reject it and return it. If it happened too often, you'd lose a customer. We lost a few customers over the years even though we had a reputation for high quality steel. Sometimes things get past them as well, and make it to the consumer. With flat rolled steel, this could show up as a pick-up truck frame, roller chain, chain saw bar, shovel, or any of a thousand other products That prematurely crack or fail.
Scale or slag gets into steel whether it is flat rolled or the bar stock that gun barrels are made of. Scale will form on red hot steel as long as we insist on making it in the presence of oxygen. Contaminants get into scrap that is melted to make steel. My company was seeing a larger than normal amount of slag formed during Electric Furnace melting and found that one supplier was cheating by filling automobiles with dirt and construction debris before baling them into little cubes. We have no proof house in this country, just a long chain of testing and inspection that can and does fail.
Sorry to be so long winded. I could go on for hours telling you about things that can and do go wrong during steel making, and I sure don't know it all. Just because fluid steel seems so pure and homogenous compared to Damascus, it would be a huge mistake to think it will always be flawless. Your gun hasn't blown up in your face yet. Does that mean it's good... or are you just lucky so far?
