Through the previous introduction of the method and specific implementation steps of directly producing gray iron castings by using water slag iron smelting, we take the direct production of gray iron castings (HT150) by using water slag iron smelting as an example: the production process of directly producing HT150 gray iron castings – small bearing seat by using water slag iron smelting is as follows:
(1) Take a certain percentage of standard gray iron raw materials used in the production of normal gray iron castings according to the mass fraction ratio, place them at the bottom of the medium frequency furnace, preheat the medium frequency furnace (the current of the medium frequency furnace is 500A ~ 600A, its power is 200kW ~ 300kW, and the time is 10 ~ 15 minutes), and then increase the power of the medium frequency furnace to full load, so that the temperature in the furnace reaches the melting temperature of gray iron, Heat for 1 hour to melt the gray iron raw material into molten iron.
(2) After the gray iron raw material is completely melted into molten iron, add the water slag iron particles screened in step 1 in a fixed proportion to the molten iron, continue to increase the power of the medium frequency furnace to full load, raise the temperature in the furnace to 1450 ℃ ~ 1500 ℃, and heat for 2 hours until the water slag iron particles in the medium frequency furnace are completely melted into molten iron.
(3) When the molten iron particles are completely melted and the distance from the molten iron surface to the furnace mouth is 10cm ~ 15cm, the molten iron shall be sampled for pre furnace test and analysis, the elements in the molten iron in the furnace shall be adjusted according to the analysis results, and a certain amount of ferrosilicon (fesi75) shall be added for conditioning to make the element content in the molten iron meet the requirements; (the carbon silicon content of molten iron is determined by the carbon silicon rapid analyzer in front of the furnace. The percentage content of C element in HT150 standard gray iron casting is 3.0 ~ 3.4, the percentage content of Si element is 1.8 ~ 2.1, the percentage content of Mn element is 0.5 ~ 0.8, the percentage content of P element is < 0.2, and the percentage content of S element is ≤ 0.12.
(4) When the molten iron is heated to 1390 ℃ ~ 1450 ℃, add 0.1% ~ 0.2% of purifying agent, 0.1% ~ 0.2% of modifying agent and 0.1% ~ 0.2% of inoculant to the molten iron, mix them and put them into the pre dried molten iron ladle. When the molten iron is out of the furnace in place, fully stir for 1 ~ 2 minutes.
(5) casting gray iron castings, placing the pre built foam pattern and pouring system in the sand box, and then pouring them. The production of HT150 bearing pedestal is a box of six pieces, which is poured from the bottom side of the bearing pedestal (bottom injection type), and the riser is set at the top of the bearing pedestal. The pouring temperature of molten iron is 1400 ~ 1450 ℃. When pouring, always fill the gate cup, and the pouring rhythm is slow fast slow. When the pouring ladle is aligned with the gate cup, slowly inject the liquid metal. When the liquid metal at the front of the pouring ladle rushes out of a channel of the pouring system, it must flow and pour continuously. When the gray iron casting is full, slow down the pouring speed until the end of pouring.
(6) After the gray iron castings are left in the air for 6 hours, turn over the box, carry out sand cleaning on the q378e hook shot blasting machine, test the performance of the gray iron castings (analyze the mechanical properties), and obtain the gray iron castings that meet the requirements. You can get the gray iron casting that meets the application requirements – HT150 small bearing seat (as shown in the figure).