1. The Scrap to Steel Billet Process
How we make our steel is a real kiwi recycling success story. The following outline is to help you to understand the scrap to steel making part of our business. All our scrap is sourced locally and is sorted and shredded on our behalf by Sims Pacific Metals – conveniently located next door to us, their biggest customer. The scrap is placed in piles in our yard, depending on its grade and size. The scrap is then loaded by a grab crane into baskets. Each “heat” is created from three basket loads of Scrap. The baskets are loaded from a recipe sheet. The first basket will hold the most scrap – 20 tons plus – and then basket two and three will progressively hold less. The target is 50 tons of scrap per heat. The first basket is lowered over the electric arc furnace and the scrap is dropped in. An electrical current is combined with chemical energy to heat the scrap to a near molten state. At this point the second basket is added and once this is also molten, the third and final basket is added. This progressive basket process is required in order to fit all the scrap in one heat We then inject oxygen and carbon and the process takes the molten metal to a base level, this also enables us to form slag on the top of molten steel. The slag (which contains the impurities we don’t want) the steel effectively bubbles off the top of the heat and is collected in a slag pit below. We process this slag and is reused as high grade roading material all around New Zealand – recycling at its best!
When the steel temperature is around 1620 degrees Celsius the molten steel is then poured into a ladle- this is called tapping. During the tapping process we add lime, manganese, silicon, carbon and if necessary depending on what type of steel is being made, vanadium. The ladle is then transported by crane to the refining station, where more carbon, manganese, silicon and vanadium are...