Practice and precautions for using carburizer in medium frequency induction heating machine melting

(1) Use charcoal to add carbon. Due to local conditions, a certain factory does not have carburizing agent and pig iron, but has a large amount of scrap steel and charcoal. The former is very expensive and difficult to buy if you have money, while the latter is very cheap and easily available. Therefore, charcoal is used to carbonize and smelt scrap steel to produce low-chromium cast iron grinding balls for mining.

① Test on charcoal addition method. The main chemical component of charcoal is carbon. Compared with carburizers, it has lower sulfur and phosphorus content. In theory, it should be a good carburizer. However, charcoal has a low density and easily floats up in molten steel. In addition, charcoal has a low ignition point and is burned in advance during the heating process. If no measures are taken, the carburization rate of molten steel will be very limited. In order to solve practical problems in production according to local conditions, the following tests were conducted: the smelting equipment was an It medium frequency induction furnace, the raw materials were scrapped mine structural parts A3 steel, the charcoal was roasted broadleaf wood, and the domestic titration carbon and sulfur analyzer was used for testing.

a. Add about 1/3 small scrap steel to the bottom of the furnace, add charcoal to the middle section of the furnace, and add scrap steel to hold it down on top of the charcoal. The carburization rate of every 1% of the charcoal is 0.55% to 0.65%.

b. First open the furnace to melt about 1/3 of the molten steel, then add charcoal, add scrap steel to hold it down, and continue melting. The carburization rate for every 1% of the charcoal is 0.60% to 0.70%.

c. First open the furnace to melt 1/3 of the molten steel, add charcoal, add a slag-forming agent on top of the charcoal, then add scrap steel to hold it down, and continue melting. During the melting period, the molten steel is covered with a slag-forming agent. The carburization rate of every 1% of charcoal is 0.70% to 0.83%. According to the long-term practice of Zhengzhou Gou's electromagnetic induction heating equipment manufacturer, method c. has a better carburizing effect and the highest carbon absorption rate. Melting It molten steel and adding 22kg of charcoal, the carbon content of the molten metal can reach about 1.9%. After testing before release, sometimes the ingredients need to be adjusted. It is not easy to adjust the carbon content slightly with charcoal. In this case, pig iron, waste electrodes or carburizing agents need to be used to increase the carbon content.

The size of charcoal also has a great impact on the carburization rate. If it is too large or too small, the absorption rate is relatively low. The 50mm block size has the highest carburization rate and is easy to operate. Especially when long strips and large pieces of charcoal are added to the furnace, it is difficult to cover them tightly, so the carburization rate is low.

②Production application and economic analysis. The factory produces grinding balls for mining. They are cast in metal molds and annealed at low temperature after grinding. The grinding balls are regularly planed for inspection. The average hardness is 45-50HRC, the tensile strength is 500-600MPa, and the impact toughness ak=8-15J/ cm2.

According to the long-term use statistics of ball mill ore grinding, the grinding ball crushing rate is <0.5% and the wear is <500g/t ore powder, which meets the needs of users.

The actual production ingredients are: 800kg scrap steel, 200kg recycled material, 22kg charcoal or carburizer, 6kg ferromanganese, 5kg ferrosilicon, and 5kg ferrochrome.