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Application of tar carburizing pretreating agent in gray iron cylinder block and cylinder head

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Application of tar carburizing pretreating agent in gray iron cylinder block and cylinder head

Date:2017-09-16 Author: Click:

Silicon carbide abrasive tar carburizer 4 # - 240 # is currently produced by screening method, because generally speaking, compared with hydraulic, wind, centrifugal classification and other methods, it has the advantages of high production capacity, high classification accuracy. The main tool of screening operation is screen mesh, and the sieve mesh with a certain size is used to accomplish the task of grading. For each screen layer, the material left on the screen after screening operation is called screening product, and the material through the screen hole is called screening product.

A particle can be screened through the following conditions: 1. SiC particles are smaller than sieve holes, and 2. have sufficient screening opportunities. Therefore, in the actual production process, the size of the screen corresponds to the number is also very critical. The silicon carbide sand produced by the company is also selected according to the market demand to screen different screens. There are many materials that can be used as carburizers for cast iron, such as artificial graphite, calcined petroleum coke, natural graphite, coke, anthracite and mixtures made of such materials.

1. synthetic graphite

Among all the above carburizing agents, the best quality is synthetic graphite.

The main raw material for making synthetic graphite is powdered high quality calcined petroleum coke, in which asphalt is added as binder, and a small amount of other auxiliary materials are added. After the various raw materials are combined, they are pressed and formed, and then treated in a non-oxidizing atmosphere at 2500-3000 degrees Celsius to make them graphitized. After high temperature treatment, ash content, sulphur and gas content decreased.

Because of the high price of artificial graphite products, most of the artificial graphite Carburants commonly used in foundries are chips, scrap electrodes and graphite blocks which are recycled to reduce production costs.

When smelting ductile iron, the quality of cast iron is superior to that of artificial graphite. Tar carburizing agent




2. petroleum coke

Petroleum coke is widely used as a carburizing agent.

Petroleum coke is a by-product of refined crude oil. Residue oil and petroleum asphalt from crude oil distillation can be used as raw materials for making petroleum coke. After coking, raw petroleum coke can be obtained. The output of raw petroleum coke is less than 5% of the crude oil used. The annual output of raw petroleum coke in the United States is about 30 million T. The content of impurities in raw petroleum coke is high and can not be directly used as carburizing agent.

Raw petroleum coke is spongy, needle like, granular and flowing.

Sponge petroleum coke is produced by delayed coking. Because of its high sulfur and metal content, it is usually used as fuel for calcination and as raw material for calcination of petroleum coke. Calcined sponge coke is mainly used in the aluminum industry and as a carburizing agent.

The acicular petroleum coke is produced by delayed coking from the raw material with high aromatic hydrocarbon content and low impurity content. The coke has a needle-like structure, sometimes called graphite coke, which is easy to crack. It is mainly used to make graphite electrodes after calcination.

Granular petroleum coke is hard granular, which is made from high sulfur and asphaltene content raw materials by delayed coking method, mainly used as fuel.

Fluidized petroleum coke is produced by continuous coking in a fluidized bed. It is fine granular, has no directional structure, high sulfur content and low volatile matter.

The calcination of petroleum coke is to remove sulfur, water and volatile matter. Calcined raw petroleum coke at 1200~1350 degree can make it become basically pure carbon.

The largest user of calcined petroleum coke is the aluminum industry, and the 70% is used to produce anodes for the reduction of bauxite. The calcined petroleum coke produced in the United States accounts for about 6% of the cast iron carburizing agent. According to the 13th Five-Year Plan of China's foundry industry and the requirements of national energy saving, emission reduction and environmental protection, medium frequency induction furnace will be more widely used in foundry enterprises. Melting cast iron with medium frequency induction furnace has the advantages of easy control and adjustment of temperature and composition of molten iron, low melting loss, low noise and pollution. However, there are some problems in induction furnace smelting, such as high whiteness tendency of molten iron, easy to produce supercooled graphite, unstable tensile strength of cast iron, large hardness dispersion and large fluctuation of leakage reject rate of castings. With the increasing expectation of end-users for product quality, the casting purchasers (especially the engine manufacturer) are demanding more and more high quality castings. They not only require good surface quality, high dimensional accuracy, mechanical properties to meet the technical conditions of service, but also have stable processing performance and casting quality. Qualitative and consistency put forward higher expectations. Therefore, under the condition of induction furnace smelting, how to improve the metallurgical quality of molten iron and improve the comprehensive quality of castings (especially the complex structure of engine cylinder block and cylinder head castings) is a joint effort to explore and improve the domestic casting industry.

With the development of casting technology, hot metal pretreatment process has been accepted and applied by more and more foundry enterprises. At present, the domestic pretreatment agent materials are mainly divided into two categories: SiC or SiC-based pretreatment agent, using pretreatment agent to purify molten iron, increase long-acting graphite core, improve graphite morphology and other characteristics, improve the metallurgical quality of cast iron, more used in gray iron; Ba-based, La-assisted pretreatment agent, using oxidation reverse. In principle, the nucleation particle of nodular cast iron should be increased, and the metallurgical quality should be markedly improved. It is mainly used in nodular cast iron.


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