The measures to improve the machine tool bed casting hardness
The continuous type water-cooled cupola furnace for smelting and casting machine, the general has certain requirements for the hardness of castings, usually above 180HB, to achieve the hardness condition, need to take measures, in particular:
1, increasing the tapping temperature
Hardness is related with the superheat temperature of molten iron, molten iron temperature is high, the inclusion in the less susceptible to oxidation, high hardness. In order to improve the temperature of molten iron, take the following measures:
1) the internal structure of the cupola was improved, shorten the hearth height, inlet into card waist shape, the main purpose is to improve the air strength, strengthen the bed coke combustion, so as to improve the overheating temperature of molten iron.
2) to carry out technical transformation to fan the original, improve air strength, make the bed coke combustion, improve the overheating temperature of molten iron.
3) the large quantities of coke quality, so as to reduce the cost, but also can improve the temperature of molten iron in objective.
2, grain refinement
Has a great effect on the mechanical properties of the grain size of metal. The finer the grain size, strength better metal, more uniform, the hardness of the less volatile. Need.
1) first of all, according to the characteristics of cupola furnace temperature is relatively low, selection of fine granularity inoculant 75SiFe.
2) Secondly, except for pregnant outside in front of the stove, for the 2 time was conceived in the casting process, so that more effective grain refinement.
3, alloying
1) improve machine casting hardness, generally adopts the improved w (Mn) method, but the production was found better results with Sn, because the Sn has a lower melting point (231.5 ℃), in order to reduce burning loss, which can be added to the Sn alloy in cast.
2) in addition, in order to improve the efficiency of Sn alloy addition, ingate on bed is improved, the common simultaneously double iron into the gating system, instead of double step sequence into iron casting system, thus improving, reducing the total amount of Sn, at the same time to meet the quality requirements.
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