Method for treating spheroidal graphite iron and pouring device thereof

Abstract

A method for treating spheroidal graphite iron includes the step: pouring molten spheroidal graphite iron into a pouring electrical furnace (1); covering the molten spheroidal graphite iron (5) with alkali slag (6) which is melted at high temperature and rich in alkali earth metal ion, rare earth metal ion, or mixture of them; connecting the molten spheroidal graphite iron (5) with the negative pole of the direct current source by one pole (7); connecting the alkali slag (6) with the positive pole of the direct current source by another pole (4), treating the molten spheroidal graphite iron (5) with the alkali slag (6) which is used as electrolyte. The method can prevent the spheroidized fading velocity of the spheroidal graphite iron. The pouring electrical furnace can be used for treating the molten spheroidal graphite iron.

Description

[0001]The present application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT / CN2009 / 070702, filed on Mar. 9, 2009, which in turn claims the priority of a Chinese patent application with an invention title of “Processing Method and Special Pouring Device for Avoiding Degradated Spheroidization and Pouring Temperature Drop of Liquid Spheroidal Graphite Iron during Pouring Process”, and an application number of 200810054604.9, and filed to the State Intellectual Property Office of the P.R.C on Mar. 10, 2008, and all contents thereof are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to the technical field of casting of spheroidal graphite iron, and particularly, to a processing method and special pouring device for avoiding degraded spheroidization and pouring temperature drop of liquid spheroidal graphite iron during pouring process.BACKGROUND OF THE INVENTION[0003]The spheroidal graphite cast iron is a ...

AI Technical Summary

Benefits of technology

[0007]The object of the present invention is to provide a processing method and a special pouring device for avoiding degradated spheroidization and pouring temperature drop of liquid spheroidal graphite cast iron during pouring process, which can solve the above problems, stabilize the pouring temperature, and completely avoid the degradated spheroidization, so as to reduce the rejection loss in the production of spheroidal graphite cast iron castings; meanwhile, the pouring electric furnace can greatly reduce the loss of residual magnesium in the liquid iron, so that the usage amount of nodulizer during spheroidization is obviously decreased, the life of the refractory material of furnace lining is prolonged, and the inert gas is no longer used or consumed, even the furnace body needs no sealing when a tilting type or stopper rod type pouring electric furnace is used, thus the worker's operations of furnace repairing and drossing are simplified, and the difficulties in operating and repairing the pouring electric furnace are decreased. The application of this technical device will have a significance for improving the reliability of spheroidal graphite cast iron, ensuring the long-term continuous and stable production of spheroidal graphite cast iron, and reducing the production cost of spheroidal graphite cast iron, and particularly, suitable to be promoted among enterprises that continuously produce spheroidal graphite cast iron castings on a large scale, such as casting production lines of automobile spheroidal graphite cast iron parts and centrifugal spheroidal graphite cast iron pipes, etc. The large-capacity pouring electric furnace using this technique can be further applied to production occasions for pouring large, heavy or super large thick-wall spheroidal graphite cast iron castings, such as large engineering structures, machine tool castings, large water pump castings, and nuclear fuel storage tanks.

Problems solved by technology

However, as compared with other metal materials, the spheroidal graphite cast iron has a great “pity”: the properties largely fluctuate during the process of metal solidification and forming, thus the material reliability is decreased, and particularly, for enterprises that produce products such as pipeline and automobile parts on a large scale, an outsize claim may be caused even undetected waste products of millionth occur during the entire production process, then the further development, promotion and application of the spheroidal graphite cast iron is restricted, this is because:

Since the spheroidization of the spheroidal graphite cast iron is carried out ladle by ladle after the smelting of the liquid base iron, the liquid iron of different ladles may have different properties, and more importantly, the same ladle of liquid spheroidal graphite cast iron after a successful spheroidization will also encounter a degradated spheroidization due to unceasing “resulfurization” and magnesium vapor “escape”, thus the mechanical properties of the castings poured later obviously become poor, and waste castings are produced.

This greatly increases the difficulty of quality control during the factory production process, the spheroidal graphite cast iron is also regarded as unstable “low-reliability material”, and its further development is then restricted.

Since the liquid spheroidal graphite cast iron will continuously undergo the “degradated spheroidization”, the effective pouring time is very short, and pouring is usually no longer allowed in the factory about ten minutes later when the pheroidization of a ladle of liquid spheroidal graphite cast iron is completed.

Thus, the production lines of spheroidal graphite cast iron castings in China scarcely use the pouring electronic furnace, as a result, the phenomenon of temperature drop of the liquid iron is serious during the pouring process, the rejection rate related to the pouring temperature is high, the designed wall thickness of the casting is compelled to be increased artificially, and the material and energy are wasted.

Thus at present, such pouring electric furnace is mainly adopted in the casting production lines where the spheroidal graphite cast iron and the gray cast iron are alternatively used, and is not suitable to enterprises that merely produce the spheroidal graphite cast iron castings.

In addition, the air pressure pouring electric furnace requires the seal and automatic pressure adjustment of the furnace gas, thus the device structure is complex, the service and maintenance are difficult, and the material cost is high due to the consumption of argon or nitrogen all the year round.