how to improve the content of ferrite in ductile iron

In the production of ductile iron, the content of ferrite can be improved by adjusting the different aspects as following:

1.Chemical Composition

(1)Reduce the promotion or stabilizing pearlite formation elements such as Mn, V, Zr, Nb, Ti, Cr, Mo, W, Cu, Pb, Sb, etc., which two are important, one is manganese, it has a particularly adverse effect on the impact toughness and brittle transition temperature of the ink cast iron,each increase of 0.1% manganese content, the brittle transition temperature of the ball is 10 ° C ~ 12 ° C, so the low-manganese iron and scraps are selected as the raw material. Another element is Cu, although it is a neutral element, and the effect of improving the pearlite content is not obvious, but with the increase in Cu, the brittle transition temperature of the ink cast iron is increased, and the impact toughness also decreases.

(2)Moderate increases ferrite formation elements, such as: C, Si, Ca, BA, Al, Bi and other elements, which is worth mentioning that Si, Si is strongly promoted graphitized elements, which facilitates improving ferrite content, However, the amount of Si increases, the impact toughness is significantly decreased, and the Si content is increased by 01.% brittle transition temperature increases 5.5 ° C to 6 ° C, and the amount of Si is about 4%, which has all ferrite substrates, but The brittleness is very brittle, that is, it is also difficult to use under the conditions of impact load, so the Si content of the Si iron with low temperature impact performance is generally controlled at 1.6 ~ 2.0%.

2.Reduce castings with cool cooling speed

A certain ingredients of the ball, change its eutectic stage cooling speed, can change its matrix tissue in a larger range, that is, the resulting cooling speed is slower, the higher the ferrite content in the matrix tissue, the thicker castings. The slower the cooling speed, the higher the ferrite content. However, it should be prevented from being large and the grain and graphite balls are large; the molding materials are different, the thermal conductivity is different, resulting in different cooled cooling speeds, should be used for dry sand or resin sand, etc. To reduce or use cold iron, for thin-walled parts, appropriately increase the casting temperature measures to slow the cooling speed of the casting, try to extend the opening time, and the conditional can be placed, slowing the heat dissipation.

3.Heat Treatment

After the heat treatment process, the ferrite content, elongation, and impact toughness have been improved, and the annealing treatment portion element can be diffused at high temperatures, the lattice of the cast base tissue is thinner, grain fine Chemical, ferrite volume and properties are stable. At the same time, the harsh requirements of some elements in the raw material can be appropriately relaxed by the method of heat treatment. For the required or small and medium-sized castings, they can be completed.

4.The choice of specific spheroidizing agent and inoculant

(1) High stable spherulation and gestation effect: This aspect depends on the composition of the spherulating agent itself, the main elements such as Mg, RE, CA, and BA are less than ± 0.3%; on the other hand is iron water The quality of the quality, such as the stability of iron temperature, S, O content; again is the stability of the operating process, such as iron speed and the control of iron, prevent iron-water spherulating agent. 

(2) Strong ink, Mg, RE is the main gel element, and is also a strong white mouth formation element. It should be based on Mg, supplemented by RE element, and is reasonably equipped with elements such as Ca, Ba, Bi and other ink. 

(3) Lower shaped slagability, one hand should minimize the segments of the spheroidizing agent, in the pregnancy agent, such as MgO, rare earth oxide and other foreign slag. At the same time, the CA and Ba content in the spheroidizing agent, the gemmatic agents are moderate because they have strong shaped slag.

In general, just control the metallurgical quality of iron water, control the content of the amount of C, Si, Mn, CA, Ba, RE, and other elements, minimize the content of other elements as much as possible, use special spheroidizing agents, gemmate agents and supporting Process, strict process, and improve the testing means of various parameters. Then, stable production of low-temperature impact ball iron castings is not a very difficult thing. Anyang Huatuo Metallurgy as one professional supplier for the raw materials for casting and steelmaking, own rich experience in the qualified product and production, if any confused just consult us.