Quality control of Ma steel pipe fittings treatment

Quality control of Ma steel pipe fittings treatment

1、 Main factors affecting treatment effect

It is more difficult for Maanshan Iron and steel pipe to be stable than ductile iron because of its narrow requirement for proper range of modified elements. This requires that the relevant process factors must strive to minimize fluctuations. The process factors that have great influence on the treatment effect of Ma steel pipe fittings mainly include the following aspects.

1. Sulfur content of molten iron

Sulfur consumes metamorphic elements. It has a strong chemical reaction with magnesium, cerium, calcium and so on. Because of the high sulfur content in hot metal, more modifiers are sulfurized to form slag, which reduces the modification ability and leads to the failure of treatment. Therefore, pig iron and coke with low sulfur content should be selected as far as possible in the production of Maanshan Steel pipe fittings. If conditions permit, it is beneficial to take pre desulfurization measures. However, this is not to say that it is impossible to treat malleable steel pipe fittings successfully with hot metal with high sulfur content. Many factories at home and abroad can produce Maanshan Steel pipe fittings stably with cupola hot metal with sulfur content as high as 0.06-0.08%, but the amount of modified alloy is more. The experience of producing vermicular graphite cast iron with hot metal containing 0.07-0.13% sulfur is introduced. It is considered that under certain conditions, the anti spheroidizing effect of sulfur can be used to expand the range as titanium does. However, the stability of sulfur content is necessary for the treatment of Ma steel pipe fittings.

2. Temperature of hot metal treatment

The high and low temperature of molten iron has a significant effect on the absorptivity of the alloy, especially for magnesium based vermicularizing agents. The higher the temperature is, the more violent the gasification boiling of magnesium is, and the less the burning loss is. Therefore, it is better to keep the treatment temperature as low as possible. The influence of different treatment temperature on the treatment effect of Ma steel pipe fittings treated with Mg Ti composite modifier was introduced. At 1400 ℃, more than 95% of vermicular graphite and few spheres were found; at 1280 ℃, more than half of the graphite balls were found. It can be seen that the treatment temperature has a great influence on the absorption.

In the actual production, the determination of the treatment temperature must also consider the casting requirements for pouring temperature. However, the treatment temperature must be as stable as possible. If the temperature fluctuates greatly, the amount of alloy added must be adjusted properly, otherwise it is difficult to guarantee the quality of treatment.

For the rare earth vermicularizing agent, the higher the treatment temperature is, the lower the temperature is, it is not easy to homogenize, and even can not melt the alloy fully, thus affecting the treatment effect.

3. Processing operation

Because vermicular treatment is sensitive to the fluctuation of the process due to turbulence, the operation must be strict and accurate. Such as the uniformity of alloy composition, the coverage of alloy, the quantity of hot metal and alloy, the measures of slag removing and slag blocking have direct influence on the treatment effect.