Melting, casting and heat treatment of high chromium cast steel liner

1 Smelting process

First, scrap steel and pig iron are added to the 500 kg acid intermediate frequency electric furnace for melting, Then chromium, molybdenum and nickel are added to adjust the composition of molten steel. Manganese and silicon are added within 5-10 minutes before tapping. 0.05% pure aluminum is added about 2 minutes before tapping to deoxidize. The temperature of molten iron is controlled between 1 460 ℃ ~ 1 500 ℃. 1.4 kg of high-efficiency rare earth compound modifier is poured into the ladle, covered with appropriate amount of heat preservation slag agglomerate, and sedated for about 5 minutes, The pouring temperature of hot metal is controlled at 1 360 ℃ ~ 1 400 ℃

2 Casting process

The technology of organic ester sodium silicate sand is adopted

Lower box sand and core sand: original sand (40 mesh / 70 mesh) 100% + water glass 5% (accounting for the weight of original sand) + organic ester 12% (accounting for the weight of water glass) + EZK type collapsing agent 2.5% (accounting for the weight of original sand)

Upper box sand: 100% of original sand + 4.5% of water glass (accounting for the weight of original sand) + 12% of organic ester (accounting for the weight of water glass), without adding crushable agent

Sand mixing process: mix the original sand with crushable powder for 1 min → mix with organic ester for 2 min ~ 3 min → mix with water and glass for 1 min ~ 2 min → sand production

Use time of molding sand: 25 min ~ 30 min

Demoulding time: 0.5min ~ 1.5min

Using alcohol – based zircon powder coating, it is required to stir well, brush evenly twice, and ignite and dry quickly

The riser adopts floating bead insulation sleeve

The surface quality of the trial production casting is good and there is no casting defect

3 Heat treatment process

After the high chromium cast steel liner casting is cleaned, the heat treatment shall be carried out in the trolley type resistance furnace. The heat treatment process is “quenching + tempering”. The heat treatment process of the high chromium cast steel liner is very critical, because the alloying degree of the high chromium cast steel we designed is far lower than that of the mainstream high chromium cast iron, Therefore, the cost of the material is greatly reduced. In order to make up for the defect that the low degree of alloying reduces the hardness of the material, the heat treatment has been greatly improved, that is, the air cooling after high temperature heating is changed to oil cooling, that is to say, the “air cooling quenching” is changed to “oil cooling quenching”, and the rapid cooling can improve the hardness of the matrix structure of the high chromium cast steel, The purpose of tempering is to eliminate quenching stress and improve toughness

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