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Xing стали образцом холодильного заголовком стали успешными стали два
发布者:本站 发布时间:2010-06-07 15:33:48 阅读:1043次 双击自动滚屏

Generally, electric arc furnace steelmaking can be divided into five steps: raw material collection; preparation work before smelting; melting; oxidation, and reduction.

Raw material collection:

Steel scrap is the main material for electric arc furnace steelmaking. The quality of steel scrap directly influences the quality, cost, and production of steel. Therefore, steel scrap shall meet the following requirements:

(1) Steel surface should be clean, and less of rust, for the reason that sediment and other debris on steel scrap will degrade the conductive performance, extend the melting time, and also affect phosphorus removing effect during oxidation period. When the corrosion is serious or the steel scrap is stained by oil, the obtainable steel and alloy element will be less, and the hydrogen content in steel will be increased.

(2) Steel scrap shall not be mixed with lead, tin, arsenic, zinc, copper and other non-ferrous metals. Lead has great density, and low melting point. It is insoluble in liquid steel. Therefore, it is easy to deposit at bottom gap and cause steel leakage accident. Tin, arsenic, and copper are easy to make the steel to be hot and crisp.

(3) Steel scrap shall not contain sealed container, flammable & explosive material, and toxic material, so as to ensure the safety in production.

(4) Chemical composition of steel scrap should be clear. Sulfur and phosphorus content shall not be too high.

(5) Size of steel scrap shall not be too big (the cross-sectional area shall not be over 150mm ×150mm, and the maximum length shall not be over 350mm). Pig iron is generally used to increase carbon content in electric arc furnace steelmaking, and the proportioning volume is usually less than 30%.

Preparation work before smelting:

Material proportioning is an important part in electric arc furnace steelmaking process. Whether the proportioning is reasonable or not concerns whether the smelter is able to conduct smelting according to requirements of the smelting process. Reasonable proportioning can shorten the smelting time. In the proportioning, the following aspects shall be paid attention to: 1. Material proportion shall be performed after volume of each material is accurate calculated. Weighing of the material shall be accurate. 2. Size of material shall be proportionately, so that the material is easy to be fed and melt. 3. All kinds of charging materials shall be combined with each other according to different steel quality requirements and different smelting processes. 4. The material ingredients shall comply with the technological requirements.

Ordinary steel smelting method has the following element content requirements for charging materials:

(1) Carbon content. Carbon content in charging material shall be sufficient for carbon-oxygen reaction during oxidizing period, so as to remove air and foreign substances. Carbon proportioning volume shall be decided by three factors: burning damage of carbon during melting period, decarburization volume during oxidation period, and carbon increasing volume during reduction period. When the charging material is melted down, the content of carbon in steel is required to be 0.3%0.4% higher than lower limit of standard. However, the carbon proportioning volume shall not be too high, otherwise the oxidation time will be extended and the temperature of liquid steel will be too high.

(2) Silicon content. Silicon content is generally not more than 0.8% of the charging material. If the content is higher, the boiling of steel liquid will be delayed.

(3) Manganese content. Manganese may not be taken into consideration in material proportioning of general type steel smelting. Generally, manganese content is less than 0.3% after the melting down, otherwise boiling of melting pool will be delayed.

In principle, phosphorus and sulfur content is the lower the better. Phosphorus content is usually less than 0.05% after the melting down.

In order to make the charging material tight in furnace, material of big, medium, and small size shall be in reasonable proportion. Generally, small size material accounted for 15% ~ 20%; medium size accounted for 40% ~ 50%; big size accounted for 40%.

Lime weighted about 1.5% of charging material shall be laid at furnace bottom before material charging, so as to prepare melting slag in advance. This is good for dephosphorization in early period. It reduces air absorption of steel liquid and accelerates temperature increasing.

During material loading, half of the small size material shall be laid at the bottom. All of big size material, low carbon steel scrap and refractory furnace material shall be put both above small size material and at central area of the furnace. Small       size material shall be put among big size material. Medium size material shall be put above or around big size material. Small size material shall be laid at the top of big size material. All the electrode blocks used in material proportioning shall be crushed into size of about 50mm100mm, and put at the bottom of furnace material.

ShanXi шос юаней металлургия машиностроительной компании с ограниченной ответственностью
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