Key points in EAF/LF route steel making 电弧炉/精炼炉炼钢要点

Jun 23, 2020 / 253 views

Application: this document is applicable for three phase AC EAF with top charging by scrap basket and spout taping, and may also be taken as reference for modern EAF like Consteel, Quantum, Ecoarc, CISDI-Green, SHARC. 

适用说明:本文件适用于顶装料、出钢槽出钢、三相交流电弧炉操作,也可作为新型电炉如康斯迪电炉、量子电弧炉、ECOARC、中冶节能电弧炉等操作参考。

1. Typical structure and work flow of EAF

典型电弧炉结构图纸

1. Typical data of 100% scrap charged EAF/LF steel making route

全废钢电弧炉/精炼炉炼钢流程典型数据

1. Raw materials preparation

原料准备


3.1 Scrap is major raw materials for EAF steel making, and account for 55~80% of total cost, so its quality is directly related with finished steel quality, production cost and efficiency.

废钢是电炉钢炼钢的主要原料,一般占到总成本的55~80%, 所以废钢的质量直接关系到钢的质量、成本和生产效率。

3.2 Scrap shall be clean and free from heavy rust, grease and oil contamination;

废钢表面应清洁少锈,无油污。

3.3 Scrap shall not contain non-ferrous elements like lead/tin/zinc/cooper, slag, non-conducting materials, refractory and others.

废钢中不得混杂铅、锡、砷、锌、铜等有色金属、炉渣、绝缘材料、耐火材料等。

3.4 For safety of production, scrap shall not contain sealed container, flammable and explosive and toxic materials.

废钢中不得混有密封容器,易燃易爆及有毒物质,确保安全生产。

3.5 Chemical composition of scrap shall be clear, no excess content of sulfur and phosphorus.

废钢化学成本应明确,硫、磷含量不能过高。

3.6 Size of scrap shall be suitable, say no more than 400x400mm in cross section, and no more than 1500mm in length of each piece.

废钢外形尺寸不能过大,截面积不宜超过400x400mm, 最大长度不宜超过1500mm。

3.7 Pig iron is usually charged to increase carbon content, no more than 30% of total burden.

生铁一般用于提高炉料配碳量,通常不超过炉料的30%。

2. Fettling

补炉

4.1 Usually after each heat, before materials charge, fettling is needed to repair furnace bottom, erosion part of slag line and other damaged part.

通常每炼完一炉钢后,在装料前需要补炉,目的是修复炉底、被侵蚀的渣线及其他受损部位。

4.2 Quick fettling in high temperature to enable self-sintering of fettling material, firstly furnace door and two sides of tap hole, then heavily eroded bottom part under graphite electrode, finally other parts of furnace.

高温下快速补炉,使补炉材料能自行烧结,先补容易冷却的炉门及出钢口两侧部位,然后补被侵蚀严重的电极下炉底部位,最后补其他部位。

4.3 Fettling layer shall be thin ( 20~30mm thick) for quick self-sintering.

补层要薄以利于烧结,以20~30mm厚度为宜。

3. Raw materials charging and distribution

装料、布料

5.1 Before charging, limestone(grain size: <60mm)of about 1.5~2% of total burden weight shall lay down in furnace bottom, which is for slag forming in advance, early dephosphorization and speedy heating.

进料前炉底先铺占料重1.5~2%左右的石灰(块度<60mm)以提前造熔化渣、早期去磷、减少钢液吸气和加速升温。

5.2 Carbon content shall be determined by burning loss of carbon in melting period, amount of decarbonization in oxidizing period, and recarburization amount in reducing period, basically, it shall be 0.3~0.6% higher than min. Level of finished steel in melt down period.

配碳量根据熔化期碳的烧损、氧化期的脱碳量和还原期增碳量这三个因素来确定,要求炉料熔清时,钢中碳量高出成品规格下限0.3%~0.6%

5.3 Principle: bottom dense, top loose; center uplift, around recess, no big and heavy materials in furnace door, for quick penetration and no bridge collapse.

布料原则:下部致密、上部疏松,中间高、四周低,炉门口无大料,这样穿井快、不搭桥。

5.4 Burden shall be dense enough and need reasonable collocation of heavy, medium and light scrap (usually, heavy scrap thickness≧15mm, 15mm>medium scrap thickness≧6mm, light scrap thickness≦4mm), say 15~20% of light scrap, 40~50% of medium scrap, 40% of heavy scrap.

During charging, 1/2 of light scrap shall lay down in bottom, above it ( in central part of EAF) heavy scrap, low carbon scrap and infusible materials shall be placed, then medium scrap shall be place above it and circumferential, finally, light scrap shall be place on the top.

炉料应密实,大、中、小料应合理搭配( 注:大料是厚度大于 15mm 的料,中料是厚度 6~15mm 的料,小料是厚度小于4mm 的料),一般小料占比15~20%, 中料占40~50%,大料占40% 。装料时,1/2小料放在底部,小料上方、炉子中心区放全部大料、低碳废钢和难熔料,中料装在大料上方及四周,大料最上方及中间放小料。

5.5 If graphite electrode breaks are used, it shall be in size of 50~100mm and placed in bottom part of each burden.

凡是配料中使用电极碎,应砸成50~100mm左右,装在炉料下方。

5.6 If the 2nd or 3th charging is needed, it shall be dry and done when the 1st burden in EAF are melt 70~90%;

需要二、三次装料时,废钢不得潮湿,不得全熔后加入,应在第一炉料熔化70-90%时进行。

4. Melting

熔化

6.1 Definition: it’s period from power on phase till that all burden are melt down, usually, it take 50~70% of total tap to tap time and 70~80% of total power consumption, so the key task of melting is to heat and melt burden with the min. power, given furnace life is guaranteed.

从通电开始到炉料完全熔化为止成为熔化期,占到总体冶炼时间的50~70%,耗电量占总电耗的70~80%左右,因此熔化期的主要任务是在保证炉体寿命的前提下,以最小的电耗快速将炉料升温熔化。

6.2 Melting can be classified into 4 steps, say: a) arc striking, b) penetration, c) lift of electrode or main meting period, d) melt down period.

熔化可以分为四个阶段,分别是 a) 起弧、b)穿井、c) 电极上升或者主熔、d) 熔清。

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6.2.1 Arc striking: medium voltage and 2/3 input of rated power of transformer is suggested for protection of furnace roof.

起弧阶段:建议选用中级电压和输入变压器额定功率的2/3左右,以免烧坏炉顶;

6.2.2 Penetration: it takes about 1/4 of total melting time, because arc is completely surrounded by scrap and little damage to lining, max. Power and current to be used.

穿井阶段:约占总熔化时间的1/4, 因电弧完全被炉料包围,使用最大功率供电。

6.2.3 lift of electrode or main meting period:it takes 50~70% of total melting time, molten pool is formed, still apply max. Power and current.

电极上升或者主熔阶段:约占总熔化时间的50~70%,底部熔池形成,仍然使用最大功率。

6.2.4 Melt down period:3/4 of charged materials has been melt, to avoid damage of roof and shell cased by strong radiation, medium voltage input is suggested.

熔清阶段:此时炉料熔化3/4以上,为避免强辐射损坏炉盖和炉壁,建议中低电压。

6.3 Typical electricity supply:

典型供电曲线图:

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6.4 Oxygen-fuel burning can start when power is on.

送电同时即开始进行氧燃助熔

1. Oxidizing period

氧化期

7.1 Task: dephosphorization, degassing, removal of impurities

主要任务:去磷、除气、去夹杂。

7.2 Principle: for oxidizing, firstly phosphorus, then carbon; in temperature, firstly low then high; in slag forming, firstly more slag for dephosphorization, then little slag for decarbonization; in oxygen supply, firstly iron ore or comprehensive oxidizing, lastly oxygen blowing.

原则:在氧化次序上,先磷后碳;在温度控制上,先低后高;在造渣上,先大渣量脱磷,后薄渣脱碳;在供氧上,可先进行矿石或者综合氧化,最后吹氧为主。

7.3 Oxygen blowing 吹氧

7.3.1 Oxygen blowing shall start after 20 min. on power time, when charged materials are melt ≧80%; graphite electrode must be lifted during oxygen blowing;

在送电20分钟后、炉料熔化≥80%以上方可吹氧助熔,助熔时必须升起电极。

7.3.2 Oxygen blowing shall be increased gradually, 0.6Mpa≦oxygen pressure≦0.8Mpa

吹氧时要慢慢开氧,吹氧压力不大于0.8MPa,不低于0.6MPa

 7.3.3 Oxygen blowing under low temperature, solid material still in furnace and partial aeration is prohibited, to avoid materials collapse, violent boiling, bulge of furnace roof, liquid steel leakage, personal or equipment accident.

严禁低温和带料氧化、局部吹氧,以防塌料和大沸腾,造成鼓炉盖、跑钢及人身设备事故

2. Reducing period

还原期

Definition: it’s time after skimming and before tapping, main task is to remove oxygen and sulfur, adjust temperature and chemical composition in liquid steel, prepare for casting.

定义:从扒渣完毕到出钢这段时间成为还原期,主要任务是尽可能的去除钢液中的氧、硫,调整钢液成分、温度,为后续浇注做准备。

* In modern EAF/LF route, whole reducing has been conducted in Lable Furnace refining process, so reducing atmosphere must be guaranteed during ladle furnace refining process, more operation key points can refer to below ladle furnace part. .

* 在现代粗炼-精炼炼钢流程中,全部还原期已经被转移到精炼炉中进行,因此务必保证精炼炉的还原氛围,更多操作要点请参考精炼炉操作部分。

3. Tapping:

出钢

9.1 Temperature of liquid steel: ≥ 1640℃

温度≥ 1640℃

9.2 Tap with reserve of liquid steel and slag, usually, reserve of liquid steel shall be 10~15% of total tap weight.

留钢留渣操作,保证每炉炉内留钢量控制在10~15%。

9.3 Argon stirring in ladle furnace shall be ready when ladle furnace are back to station after receiving liquid steel, pressure of Argon is 0.4~0.6Mpa and shall be adjusted accordingly to stirring situation.

 出钢后钢包应立即接通氩气, 氩气压力为0.4 ~ 0.6Mpa, 氩气压力大小根据钢液搅拌效果进行调整,确保钢液搅拌良好。

9.4 During tapping, when 1/3 of total liquid steel is poured, formulated ferroalloy, deoxidizer and slag forming materials shall be added into liquid steel, while, amount of ferroalloy shall be based on min. content of certain steel grade, and slag forming materials in 10kg/mt.

出钢过程中,出钢到三分之一时,加入配好的合金、脱氧剂及渣料。 合金加入量按规格中该元素含量下限配入,渣料按吨钢10Kg 加入。

4. Ladle furnace refining

精炼炉精炼操作

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Key points:

操作要点:

1.1 reducing atmosphere inside ladle furnace;

炉内还原性气氛

1.2 Good argon stirring from the bottom of furnace

良好的氩气底吹搅拌

10.3 Sub-merged arc heating

电极埋弧加热

10.4 White slag refining

白渣精炼

10.5 refining time no less than 35 mins

精炼时间不短于35分钟。

Thanks for your time and attention, because I am not metallurgical professional and just compile/edit this paper based on many known or unknown sources, there must be errors or misunderstanding in this article, welcome correction and further discussion.

感谢您阅读本文,因编者非冶金专业人士,只是根据手头已有的资料、信息汇编出本文,必有错讹疏漏之处,还望方家不吝赐教。



Tags: steel making

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