450mm graphite electrode suppliers
450mm graphite electrode suppliers processing step
Roasting: It is a process in which the green carbon product is charged into a specially designed heating furnace for high-temperature heat treatment under the maintenance of the filler, so that the coal pitch in the green body is carbonized. The pitch coke formed by the carbonization of coal pitch consolidates the carbonaceous aggregate and powder particles together, and the roasted carbon product has higher mechanical strength, lower electrical resistivity, better thermal stability and chemical stability .
Roasting is one of the primary processes in the production of carbon products, and it is also an important part of the three heat treatment processes in the production of 450mm graphite electrode. The roasting cycle is longer (22-30 days for the first baking, 5-20 days for the second baking). And the energy consumption is higher. The quality of the green body firing has a certain impact on the quality of the finished product and the production cost.
The coal pitch in the green body is coked during the roasting process, and about 10% of the evaporated content is discharged. Together, the volume shrinks by 2-3%, and the mass is lost by 8-10%. The physical and chemical functions of the carbon billet have also undergone significant changes, as the porosity increases and the volume density is reduced from 1.3 to 1.3, and the resistivity μΩ·m drops to 40-50 μΩ·m, and the mechanical strength of the calcined billet is also greatly improved.
Secondary roasting is a process in which the roasted product is immersed and then roasted again to carbonize the pitch immersed in the pores of the roasted product. The production of electrodes with higher bulk density requirements (all varieties except RP) and joint blanks need to be subjected to two baking, and the joint blanks also need to be subjected to three immersion and four baking or two immersion and three baking.
Main furnace type of roaster:
Continuous operation-ring furnace (with or without cover), tunnel kiln
Intermittent operation-inverted flame kiln, car bottom roaster, box roaster
Roasting curve and maximum temperature:
One-time roasting-320, 360, 422, 480 hours, 1250 ℃
Secondary roasting-125, 240, 280 hours, 700-800 ℃
View of baked products: appearance knock, resistivity, bulk density, compressive strength, internal structure analysis
Impregnation is a process in which the carbon material is placed in a pressure vessel, and the liquid impregnant pitch is immersed into the electrode pores of the product under certain temperature and pressure conditions. The intention is to reduce the porosity of the product, increase the volume density and mechanical strength of the product, and improve the electrical and thermal conductivity of the product.
The impregnation process and related technical parameters are: baking billet-surface cleaning-preheating (260-380 ℃, 6-10 hours)-loading into the impregnation tank-vacuuming (8-9KPa, 40-)- —Inject asphalt (180-200 ℃) — pressurize (1.2-1.5MPa, 3-4 hours) — return asphalt — cool (in or outside the tank)
View of impregnated products: impregnation weight gain rate G=(W2-W1)/W1×100%
Weight gain rate of one-time impregnation product≥14%
Weight gain rate of secondary dipping product≥9%
Weight gain rate of three dipping products ≥5%