外文翻譯--寶鋼堿性氧氣轉(zhuǎn)爐煉鋼生產(chǎn)及潔凈鋼控制

1、<p>　　內(nèi) 蒙 古 科 技 大 學</p><p>　　畢 業(yè) 設 計 外 文 翻 譯</p><p>　　專 業(yè)： 冶金工程</p><p>　　班 級： 冶金一班</p><p>　　學 號： 0868100211</p><p>　　姓 名： 包春鋼</p>&

2、lt;p>　　導 教： 趙永旺</p><p>　　Basic oxygen furnace based steel-making processes and cleanliness control at Baosteel</p><p>　　L. Zhang*1, J. Zhi2, F. Mei2, L. Zhu2, X. Jiang2, J. Shen2, J. Cui2,

3、 K. Cai3 and B. G. Thomas4</p><p>　　Optical microscopy, total oxygen measurements and slime tests have been conducted to quantify the size distribution and amount of inclusions at various processing steps du

4、ring basic oxygen furnace (BOF) based steel production at Baosteel. The effects on steel cleanliness of specific operational improvements during steel refining and continuous casting have been investigated. Such improvem

5、ents to these processes and the resulting level of steel cleanliness at Baosteel are summarised in the presen</p><p>　　Keywords: Clean steel, Inclusions, Impurity elements, Interstitial free steel, Line pipe

6、 steel</p><p>　　Introduction</p><p>　　The importance of clean steel in terras of product quality is increasingly being recognised. Clean steel requires control of the size distribution, morpholo

7、gy and composition of non-metallic oxide inclusions in addition to the amount. Furthermore, sulphur, phosphorus, hydrogen, nitrogen and even carbon[1,2] should also be controlled to improve the steel properties. For exam

8、ple, ,formability, ductility and fatigue strength worsen with increasing sulphide and oxide inclusion contents. Lowering the</p><p>　　Baoshan Iron & Steel Co., Ltd (Baosteel) is currently the largest ste

9、el company in China. Its annual steel production was 115 million tonnes in 2003, 119 million tonnes in 2004 and 14.0 million tonnes in 2005. With regard to the basic oxygen furnace (BOF) based steelmaking route, there ar

10、e three 300 t and two 250 t BOFs; several steel refining units, including one CAS-OB unit (controlled argon stirring-oxygen blow), two RH (Ruhrstahl-Heraeus) degassers and one ladle furnace (LF). Since 1990, eff</p>

11、;<p>　　Experimental method and examination of inclusions in steel</p><p>　　Experimental methods</p><p>　　Ladle steel samples were taken 500-600 mm below the top slag in the ladle, tundish

12、 steel samples from 300 mm above its outlet and mould steel samples from 150 mm below the meniscus and 300 mm away from the submerged entry nozzle (SEN) outports. The sampler was a cylindrical steel cup with a cone shape

13、d copper cover to protect it from slag entrainment during immersion. Attached to a long bar, the sampler was immersed deep into the molten steel, where the copper melted and the cup was filled. Smal</p><p>　

14、　Fig.1 Sampling locations for continuously cast slab: TO total oxygen</p><p>　　In the present work, 'macroinclusions' were those greater than 50 um in diameter. Most of these were detected in the re

15、sidues extracted by electrolytic isolation ('slime test') from the larger steel samples. The 'microinclusions' data derive from microscopic assessments carried out on planar sections, most of which were

16、 smaller than ~50 μm</p><p>　　Morphology and composition of typical inclusions</p><p>　　The morphology ,composition and likely sources of typical inclusions found in LCAK steel samples form the

17、ladle ,tundish and mound are shown in Figs.2 and 3 respectively.The morphologies included: (a) angular aluminate(Fig.2 d and f and Fig.3b);(b)alumina cluster (Fig.2b and c);and (c) spherical silicate (Fig. 2a and c and F

18、ig. 3a).</p><p>　　a. ladle; b. tundish; c,d. mound; e,f. slab </p><p>　　Fig.2 Typical inclusions from given samples examined by microscope</p><p>　　(a) tundish

19、 (b) slab</p><p>　　Fig. 3 Typical inclusions from given samples extracted using slime method </p><p>　　The possible sources were deoxidation products, reoxidation products o

20、r broken refractory lining bricks. In line pipe steel, besides these common inclusions, many nanoscale TiN inclusions were found along grain boundaries. These nano TiN changed from square to ellipsoid if combined with Ti

21、2O3 , as shown in Fig. 4 [5]</p><p>　　a . compound inclusions with composition Ti2O3+MnS ; b. TiN inclusion</p><p>　　Fig.4 Nanoprecipitates in line pipe steel</p><p>　　Total oxyge

22、n measurement is an indirect method of evaluating oxide inclusions in a steel.3 The total oxygen (TO) in the steel is the sum of the free oxygen (dissolved oxygen) and the oxygen combined as non-metallic inclusions. Free

23、 oxygen, or 'active' oxygen, can be measured relatively readily using oxygen sensors. It is controlled mainly by equilibrium thermodynamics with deoxidation elements, such as aluminium. If [%A1] =0.03-0-06, the f

24、ree oxygen is 3-5 ppm at 1600°C. Because the free oxygen </p><p>　　Fig.5 Total oxygen in steel from ladle to slab </p><p>　　Ladle operations to remove more inclusions</p><p>　

25、　Ladle slag reduction treatment</p><p>　　Reoxidation to form alumina in the ladle during steel refining is mainly caused by Si02 in the slag and lining refractory, and MnO and FeO in the ladle slag, by the f

26、ollowing reactions:</p><p>　　3/2(Si02) + 2[Al]=(Al203) + 3/2[Si] </p><p>　　3(MnO) + 2[Al]s = (Al203) + 3[Mn] </p><p>　　3(FeO) + 2[Al]s = (A1203) +3[Fe]</p><p>　　Slag re

27、duction treatment is carried out by adding aluminium and lime onto the top of the ladle slag to reduce its FeO and MnO content. The effect of ladle slag reduction treatment on the TO content in the steel is shown in Fig.

28、 6. A larger FeO + MnO content in the ladle slag corresponds to higher total oxygen. With the slag reduction treatment, MnO and FeO in the ladle slag were reduced to <5%, corresponding to <20 ppm TO in the tundish.

29、</p><p>　　Fig.6 Effect of FeO and MnO content in ladle slag on TO in steel</p><p>　　Calcium treatment</p><p>　　Nozzle clogging induces serious castability problems in aluminium kil

30、led steels, such as lowering the casting speed, inducing asymmetrical fluid flow and level fluctuations in the mould, thus entrapping more inclusions, and sometimes causing a breakout. Removing more inclusions before co

31、ntinuous casting is the best way to prevent nozzle clogging , and is the only approach for steels with very strict requirements on formability [6]. </p><p>　　At Baosteel, CaSi wire is fed into the molten ste

32、el during ladle refining. Alumina reacts with CaO, forming calcium aluminates. Tf the generated calcium aluminates have a low melting point, then clogging is improved. The possible compound inclusions generated by calciu

33、m treatment include CA6, CA2, CA, Ci2A7 and C3A, where C and A represent CaO and A1203, respectively. The first two should be avoided owing to their high melting point over 1700°C. </p><p>　　Current pra

34、ctice at Baosteel indicates that [Ca] should be >25 ppm in order to prevent solid alumina based inclusion clogs . Too much calcium can also generate CaS with a high melting point (2450°C). Too much sulphur in the

35、 steel and too low a temperature also enables CaS generation. Baosteel practice indicates that <50 ppm [Ca] in the steel can prevent CaS generation, and [Ca]/[Al]>0.09 favours prevention of nozzle clogging (Fig. 1

36、7). Hence, [Ca] needs to be controlled within the range 25-50 p</p><p>　　Control of nitrogen, carbon, sulphur and phosphorus in steel</p><p><b>　　Nitrogen</b></p><p>　　N

37、ormally, a large nitrogen content at tapping tends to result in a large nitrogen content in the slab. Thus, the control of nitrogen should mainly focus on lowering the nitrogen content during BOF blowing and preventing n

38、itrogen pickup during tapping, steel refining and continuous casting. Currently, at Baosteel, nitrogen during BOF steelmaking fluctuates from 11 to 43 ppm. Plant experiments indicate that when [N] is less than 30 ppm bef

39、ore RH treatment, [N] cannot be lowered further by RH tre</p><p><b>　　Carbon</b></p><p>　　The greatest decarburisation is for IF steel by converter treatment which can reach to hig

40、her than 90% and further decarburization for IF is by RH. Techniques to improve this operation include:</p><p>　　(1) optimising initial [C] and [O] before degassinginto the ranges of 500-650 ppm and 300-450

41、 ppm, respectively.</p><p>　　(2) enlarging the snorkel diameter from 500 to 750 mm and increasing the argon flowrate from 1000 to 3000 NL minT-1. After this treatment, [C] can be lowered to10ppm.<

42、;/p><p>　　The [C] pickup occurring during continuous casting is controlled below 6 ppm by the following techniques: </p><p>　　(4)using low carbon, high viscosity mould flux, decreasing carbon pick

43、up at the continuous casting mould from 5.5 to 1.8 ppm.</p><p>　　(5) using carbon free ladle refractory lining</p><p>　?。?）using high basic, low carbon tundish flux (CaO/SiO2>4)</p>&l

44、t;p><b>　　Sulphur</b></p><p>　　The initial sulphur content of the molten iron at Baosteel is ~200 ppm. After hot metal desulphurisation by injection of CaC2 powder or magnesium based powder, th

45、e sulphur decreases to 10-30 ppm. It is important to remove the top slag quickly after desulphurisation in order to decrease sulphur pickup. During the BOF steelmaking process, there is 10-30 ppm sulphur pickup, mainly f

46、rom lime and scrap. To achieve an ultralow sulphur content, especially for line pipe steels, three desulphurisation me</p><p>　　(1) CaO-CaF2 flux is added to the vacuum chamber through the alloy addition hop

47、pers; slag carryover from the BOF is controlled carefully for these heats, and ladle slag reduction treatment is carried out to decrease the FeO content in the slag before steel desulphurisation; [S] is lowered from 28.

48、4 to 16.2 ppm </p><p>　　(2) After strong deoxidation, CaO-CaF2 powder is injected into the molten steel in the ladle by a lance below the up snorkel; [S] can be lowered from 61.9 to 35.8 ppm </p><

49、p>　　(3) A suitable emulsification condition, improving the reaction between slag and molten steel; [S] can be lowered from 67.0 to 8.7 ppm. This method can lower the sulphur below 10 ppm, so is currently used for the

50、production of ultraclean line pipe steel. It should be noted that the MgO-CaO refractory lining and tundish flux may also remove some sulphur by the following reaction:</p><p>　　(CaO)+2/3[Al]+[S]=(CaS)+1/3[A

51、l2O3]</p><p>　　Phosphorus</p><p>　　Five different processing routes are used to achieve low phosphorus steel at Baosteel: (1) de-Si, de-P and de-S at hot metal treatment,followed by BOF steelmak

52、ing with a small slagcontent, lowering [P] to 120 ppm .</p><p>　　(2) de-S at hot metal treatment, then the BOFprocess with a large slag content, lowering [P] to100 ppm.</p><p>　　(3) de-Si, de-P

53、 and de-S at hot metal treatment,followed by BOF steelmaking with a large slagcontent, lowering [P] to66 ppm .</p><p>　　(4) de-P at hot metal treatment, followed by BOFsteelmaking with a large slag content,

54、 lowering [P] to 58 ppm .</p><p>　　(5) double BOF steelmaking process, achieving 20 ppm [P] in the steel. </p><p>　　The control of impurity elements at Baosteel has improved considerably during

55、the past 15 years, as indicated in Table 1. Baosteel steel can now achieve TO<16ppm, [S]<5 ppm, [P]<35 ppm, [N]<29 ppm, [H]<1 ppm in line pipe steel, and [C]<16 ppm, TO<19ppm, [N]<15ppm in IF stee

56、l. Currently, [S] + [P] + TO + [N] + [H] in line pipe steel can be maintained below 85-5 ppm, and [C] + TO + [N] in IF steel can be kept below 50 ppm.</p><p>　　Table 1 Impurity content of line pipe steel a

57、nd interstitial free </p><p>　　(IF)steel achieved at Baosteel,ppm </p><p>　　Conclusions</p><p>　　Techniques to improve steel cleanliness at Baosteel include ladle slag reduction tre

58、atment to lower FeO and MnO in the ladle slag to below 5% before steel refining, suitable CaSi wire injection in the ladle, ladle slag detection during pouring, development of a CaO based basic tundish flux, optimisation

59、 of flow control devices in the tundish and optimisation of mould flow to avoid mould slag entrainment.</p><p>　　Inclusions concentrate mostly within 20 mm of the slab surface. Some slabs experience occasion

60、al accumulation at one-quarter to one-half slab thickness from the inner radius.</p><p>　　Castability has been improved by an improvement of steel cleanliness, the use of optimal calcium treatment to preven

61、t nozzle clogging and application of a breakout prediction system at the caster.</p><p>　　Currently, the impurity elements in steel can be controlled to TO<16 ppm, [S]<5 ppm, [P]<35 ppm, [N]<29 p

62、pm, [H]<1 ppm for line pipe steels, and [C]<16 ppm, TO<19 ppm, [N]<15 ppm for IF steels.</p><p>　　References</p><p>　　1．K．W．Lange：Int．Mater．Rev．19883．3，53-89．</p><p>　　2

63、．W．B．Morrison．Ironmaking Steelmaking．1989．16．123-130．</p><p>　　3．L．Zhang and B．G. ．Thomas:ISIJ Int,2003．43．271-291．</p><p>　　4．A．W．Cramb:in ‘Impurities in engineered materials:impact,reliability

64、 and control’ ,(ed ,C．L．Briant) ．49-89:1999．New York,Marcel Dckker．</p><p>　　5．Q．Zheng,Z．Chen and L．Zhu Proc 13th CSM Annu ．Steelmaking Conf ． Kunming,China2004 , Chinese Society for Metals．</p><p

65、>　　6．K．Larsen and R．J．Fruehan:Iron Steelmaker(ISS Trans),1991．12,125-132．</p><p>　　7．K．Sasai and Y．Mizukami: ISIJ Int．2000．40．40-47．</p><p>　　8．N．Bannenberg and K．Harste:Rev．Metall．Cah．Inf．T

66、ech．1993．90．71-76．</p><p>　　寶鋼堿性氧氣轉(zhuǎn)爐煉鋼生產(chǎn)及潔凈鋼控制 </p><p>　　寶鋼通過在光學顯微鏡下對總氧量的測量和礦渣分析來對堿性氧氣轉(zhuǎn)爐雜質(zhì)的形態(tài)分布和不同生產(chǎn)階段夾雜的種類進行定性分析。同時對精煉和連鑄的操作過程對鋼的純凈度的影響也進行了研究。 有關這些改善過程和寶鋼的潔凈鋼資料可參閱相關文獻。盛鋼桶的還原渣可以使渣中的FeO+MnO總量小于5

67、%，也可以避免鋼液的二次氧化。在鋼包中通過喂CaSi線來改善夾雜物的形態(tài)，并且在連鑄過程中對鋼渣進行檢測。中間包流量控制以及CaO/SiO2>4的高含量等技術來進一步去除雜質(zhì)。隨著堿性氧氣轉(zhuǎn)爐煉鋼過程的發(fā)展，管線鋼雜質(zhì)含量可控制在總氧 (TO)<16ppm, [S]<5ppm, [P]<19ppm, [N]<15ppm [H]<1ppm。 IF 鋼可達到[C]<16ppm, TO<19pp

68、m, [N]<15ppm。</p><p>　　關鍵詞：潔凈鋼 夾雜 雜質(zhì)元素 超沖深無間隙原子鋼 管線鋼 </p><p><b>　　引言： </b></p><p>　　潔凈鋼質(zhì)量的重要性正逐步得到人們的認可。潔凈鋼除了對雜質(zhì)總量的要求外還要求對非金屬氧化物夾雜的形狀分布，形態(tài)和組成進行控制。另外，還對 S, P, H,

69、N甚至 C 進行控制來進一步提高鋼的性能[1,2]。例如，硫化物和氧化物夾雜會使鋼的可鍛性、塑性和疲勞強度惡化，降低碳、氮含量會提高鋼的應變時效以及塑性和韌性，磷含量的降低對淬透性和抗回火脆性均有所改善?！皾崈翡摗备鶕?jù)鋼號的不同可以有多種要求。例如：IF 鋼要求 C 和 N 總量 < 30ppm；管線鋼要求S, P, 和 TO < 30ppm，低 H 低 N 和適當?shù)?Ca/S；軸承鋼要求總氧量 < 10ppm[3]。

70、另外，許多用途都要限制夾雜物的最大形狀[3,4]，因此對雜質(zhì)的形狀分布也有重要要求。</p><p>　　寶鋼是中國最大的鋼鐵企業(yè)，2003年產(chǎn)鋼量為 1150 萬噸，2004年 1190 萬噸，2005年達到 1400 萬噸。煉鋼系統(tǒng)現(xiàn)有3座300噸，2座250噸堿性氧氣轉(zhuǎn)爐。精煉設施包括1座 CAS-OB，2座RH精煉爐和1座LF精煉爐。1990年以來，潔凈鋼的研究主要集中在煉鋼過程中對TO, N, S ,

71、P, H 和C的含量控制來生產(chǎn)鋁脫氧低碳鎮(zhèn)靜鋼(LCAK)。LCAK鋼和IF 鋼工藝流程為 BOF—RH—CC ；管線鋼流程為 BOF—RH—LF—CC。</p><p>　　實驗方法和鋼中雜質(zhì)元素檢測：</p><p><b>　　實驗方法：</b></p><p>　　鋼包鋼樣從鋼渣液面以下500~600mm處取樣，中間包鋼樣自出口300m

72、m以上處取樣，結(jié)晶器鋼樣由液面150mm以下，離浸入式水口300mm處取樣。試樣做成帶圓錐形銅罩的圓柱形鋼杯，以防進入時被鋼渣沖掉。試樣綁在一個長桿上深入熔池，待銅罩融化后鋼液便進入鋼杯。小金屬試樣長80mm，直徑30mm，加工成5（直徑）×5mm圓柱試樣，分析總氧和氮含量，20（直徑）×15mm圓柱試樣進行顯微鏡微觀分析，加工所產(chǎn)生的鋼屑用于C, P, S 含量分析。鋼包和中間包的大試樣長200 mm，直徑50 m

73、m，加工成60（直徑）×150mm圓柱。</p><p>　　如圖1所示總氧和氫含量測定。這個分析包括渣樣和鋼樣的化學組成，細微夾雜物的顯微觀測，渣泥中提取的宏觀夾雜物以及夾雜物的表面形態(tài)和組成的掃描電子顯微鏡分析。</p><p>　　圖 1 板坯試樣：總氧量</p><p>　　現(xiàn)階段，所謂宏觀夾雜是指直徑大于50μm的夾雜，大部分從鋼樣殘泥中電解

74、析出（泥漿測試法）；大部分小于50μm的微觀夾雜的數(shù)據(jù)是由顯微鏡觀測到的平面部分。</p><p>　　典型夾雜的表面形態(tài)和組成</p><p>　　LCAK鋼樣中典型夾雜的表面形態(tài)，組成和來源如圖2，圖3所示。這些表面形態(tài)包括 ：(a) 呈角狀的鋁酸鹽（圖2 d和f，圖3 b）；(b) 氧化鋁簇（圖2 b和e）和(c)球狀硅酸鹽（圖2 a和c，圖3 a）。</p><

75、p>　　圖2 a 鋼包； b 中間包； c d 結(jié)晶器； e f 板坯</p><p>　　(a)中間包 (b)板坯</p><p>　　圖 3 泥漿法提取的試樣中的典型夾雜</p><p>　　這些物質(zhì)可能為脫氧產(chǎn)物，二次氧化產(chǎn)物或殘余的耐火磚的成分。在管線鋼中，除這些普通

76、的夾雜外，在晶界處還發(fā)現(xiàn)許多極細的TiN顆粒。這些細的TiN雜質(zhì)如果和Ti2O3化合則他們的形狀將由方形轉(zhuǎn)變?yōu)闄E圓形， </p><p><b>　　圖 4</b></p><p>　　如圖4所示[5] a. 由Ti2O3+MnS組成的復合夾雜； b. TiN夾雜</p><p>　　鋼中總

77、氧量的測量是通過估測鋼中氧化物夾雜而間接測量的[3]?？傃趿縖TO]是鋼中自由氧（未溶解的氧）和與金屬夾雜結(jié)合的氧的總和?！白杂裳酢庇址Q為活氧，可由氧傳感器方便的測出。它主要受脫氧元素如鋁的熱力學平衡所控制。 1600ºC時，如果[%Al]=0.03~0.06，則自由氧含量為3~5 ppm。由于自由氧含量比較穩(wěn)定，這樣可以間接測量鋼中氧化物夾雜總量。實驗中由于測量總氧的試樣比較小并且雜質(zhì)中氧化物含量不高，因此試樣中很少

78、能找到大的氧化物夾雜，即使試樣中包含了大的夾雜也會由于讀數(shù)偏大而無法測量。這樣一來，總氧含量實際上僅僅代表了小于50μm的小氧化物夾雜的含氧量。寶鋼現(xiàn)在的IF 鋼和管線鋼中的總氧含量已小于16 ppm。兩套系統(tǒng)中鋼包，中間包，結(jié)晶器和板坯中的的總氧含量如圖5所示，表明總氧量從鋼包到中間包，結(jié)晶器，連鑄坯依次減少。</p><p>　　圖 5 從鋼包到板坯的總氧量</p><p>　　鋼包操

79、作進一步去雜：</p><p><b>　　鋼包還原渣處理：</b></p><p>　　鋼包中由爐渣和耐火材料內(nèi)襯產(chǎn)生的SiO2以及鋼包渣中MnO和FeO和Al反應生成Al2O3，反應如下：</p><p>　　3/2(Si02) + 2[Al]=(Al203) + 3/2[Si] </p><p>　　3(MnO)

80、+ 2[Al]s = (Al203) + 3[Mn] </p><p>　　3(FeO) + 2[Al]s = (A1203) +3[Fe]</p><p>　　通過向鋼包渣中加入鋁和石灰來降低渣中FeO和MnO含量的方法來造還原渣，這個還原反應對鋼渣中的總氧含量的影響如圖6所示。鋼渣中隨FeO和MnO含量升高則總氧量也升高。在所造的還原渣中，渣中的MnO和FeO減少到小于5%，對應中間包

81、中的總氧量小于20 ppm。</p><p>　　圖 6 鋼渣中FeO和MnO的含量對總氧的的影響</p><p><b>　　鈣處理</b></p><p>　　鋁脫氧鎮(zhèn)靜鋼中如果水口堵塞會引發(fā)一系列問題，如降低拉速，產(chǎn)生不對稱液流，結(jié)晶器鋼液面波動等導致夾渣，有時還會發(fā)生漏崗。防止水口堵塞最好的方法是連鑄前去除盡量多的雜質(zhì)，并且這是對于嚴格

82、要求鋼的韌性的可行性的唯一手段[6]。 </p><p>　　寶鋼精煉時向鋼液中喂入CaSi線，氧化鋁和氧化鈣生成鋁酸鈣，如果生成的鋁酸鈣熔點低則可以使水口堵塞問題得到改善。該處理可能生成的化合物包括CA6，CA2，CA，C12A7和C3A，C和A分別代表CaO和Al2O3。由于前兩個熔點高于1700ºC所以應該避免。</p><p>　　寶鋼研究表明為防止固體Al2O3堵塞應使

83、[Ca]大于25ppm。但太高的Ca會產(chǎn)生高熔點的CaS（2450ºC），太高的S或太低的溫度也會產(chǎn)生 CaS。實踐證明鋼中[Ca] <50 ppm時會阻止CaS的生成，并且[Ca]/[Al]>0.09時也會防止堵塞。因此鈣應在25~50 ppm范圍內(nèi)，并且[Ca]/[Al]>0.09。</p><p>　　鋼中氮，碳，磷，硫的控制</p><p><b&

84、gt;　　氮</b></p><p>　　通常情況下由于出鋼時鋼水含氮量高而導致板坯中含氮量高，因此應注重在轉(zhuǎn)爐吹煉過程中降氮，防止出鋼過程中增氮以及在精煉和連鑄過程中對氮進行控制。寶鋼堿性氧氣轉(zhuǎn)爐煉鋼條件下可使氮含量波動在11~43 ppm之間，實驗證明在精煉前當[N]<30ppm時，不能通過RH精煉而使其進一步降低。由于在空氣/鋼界面動力學條件比較優(yōu)越而導致鋼的增氧量通常比增氮量大很多[7]

85、。另外，氧和硫含量低時增氮量會隨之增加[8]，因此寶鋼在現(xiàn)場操作中采用出鋼后進行脫氧的方法來有效的防止增氮。如今，IF鋼和管線鋼的含氮量已經(jīng)達到15~30ppm，通過中間包加覆蓋渣，吹氬和密封等方法使從鋼包到中間包過程的增氮量控制在1.5ppm以下。</p><p><b>　　碳</b></p><p>　　轉(zhuǎn)爐是IF鋼脫碳最多的環(huán)節(jié)，可達到90%以上。進一步脫除可

86、用RH進行，這個操作過程的改善包括：</p><p>　　（1）脫氣前最佳[C]和[O]含量分別應達到500~650ppm和300~450ppm；</p><p>　?。?）將連通管的直徑從500 mm增加到750 mm，N2流量從1000增加到3000NL/min；[C]含量可降低到10ppm 通過下列措施可使連鑄過程的增[C]控制在6 ppm；</p><p&g

87、t;　　（3）是用低碳結(jié)晶器保護渣，使連鑄過程增碳從5.5降到1.8 ppm；</p><p>　　（4）用不含碳的鋼包耐火材料；</p><p>　?。?）用高堿度，低碳的中間包覆蓋渣</p><p><b>　　硫</b></p><p>　　寶鋼鐵水初始含硫量為200 ppm左右，通過加入CaC2粉末或鎂基合金進行

88、脫硫后，硫含量可以達到10~30 ppm。為降低鋼水回硫應將脫硫后的爐渣盡快扒去，轉(zhuǎn)爐冶煉過程會增加10~30 ppm的硫，主要是由于所加的石灰和廢鋼帶入。為得到超低硫鋼特別是管線鋼，現(xiàn)已發(fā)展了3種脫硫方法：</p><p>　?。?）通過料斗向真空室加入CaO-CaF2溶劑，轉(zhuǎn)爐出鋼中所帶的部分夾渣可以得到有效控制并且在鋼水脫硫前造還原渣以減少FeO含量，可使[S]含量從28.4降低到16.2 ppm；<

89、/p><p>　　（7）脫硫后CaO-CaF2粉末通過氧槍吹入熔池，[S]含量從61.9降低到35.8 ppm；</p><p>　?。?）適當?shù)娜榛饔每梢栽黾愉撍蜖t渣之間的反應；可以使[S]含量從67.0降低到8.7 ppm；此方法可以使硫降到10 ppm一下，因此可以生產(chǎn)超純凈管線鋼。還應該注意到MgO-CaO耐火材料內(nèi)襯和中包渣也能脫除部分硫</p><p>

90、　　(CaO)+2/3[Al]+[S]=(CaS)+1/3[Al2O3]</p><p><b>　　磷</b></p><p>　　寶鋼生產(chǎn)低磷鋼的五種路線：</p><p>　　（1）減少轉(zhuǎn)爐爐渣量以便于在鋼水中進行脫Si, P ,S,可以使[P]含量降到120ppm；</p><p>　　（2）先在鋼水中脫S，然后

91、增加轉(zhuǎn)爐爐渣量，可以使[P]含量降到100ppm；</p><p>　?。?）在熔池中脫Si, P ,S，增加轉(zhuǎn)爐渣量可以使[P]含量降到66ppm；</p><p>　?。?）在熔池中脫P ，增加轉(zhuǎn)爐渣量可以使[P]含量降到58ppm；</p><p>　?。?）雙轉(zhuǎn)爐煉鋼過程，可以使[P]含量達到20 ppm。</p><p>　　過去1

92、5年中寶鋼在控制鋼中夾雜物方面取得了很大進步。如表1所示</p><p>　　現(xiàn)在可以達到 管線鋼 TO<16ppm，[S]<5ppm，[P]<35ppm，[N]<29ppm，[H]<1ppm，IF 鋼中 [C]<16ppm，TO<19ppm，[N]<15ppm；</p><p>　　管線鋼[S]+[P]+TO+[N]+[H]可低于85.5

93、ppm</p><p>　　IF鋼中[C]+TO+[N]可低于50ppm。</p><p>　　寶鋼管線鋼和IF鋼中雜質(zhì)含量</p><p><b>　　結(jié)論：</b></p><p>　　寶鋼提高鋼純凈度的技術包括：精煉前在鋼包中造還原性渣的方法使FeO和MnO含量降到<5%，在鋼包中合喂CaSi線，澆注過程中鋼

94、包渣中檢測，以CaO為基礎的堿性中間包熔劑。設置流量控制裝置避免結(jié)晶器下渣。；</p><p>　　雜質(zhì)大部分集中在板坯表面以下20mm處，一些偶爾集中在鑄坯內(nèi)半徑的1/4處；</p><p>　　由于鋼潔凈度的提高而使連鑄性能得以改善。用鈣處理的方法以防止水口阻塞，并且應用了漏鋼預報系統(tǒng)；</p><p>　　現(xiàn)今，雜質(zhì)元素可被控制在：管線鋼 TO<16pp

95、m, [S]<5ppm, [P]<35ppm, [N]<29ppm ，[H]<1ppm; IF鋼 [C]<16ppm, TO<19ppm, [N]<15ppm。</p><p><b>　　參考文獻：</b></p><p>　　1．K．W．Lange：Int．Mater．Rev．19883．3，53-89．</p&

96、gt;<p>　　2．W．B．Morrison．Ironmaking Steelmaking．1989．16．123-130．</p><p>　　3．L．Zhang and B．G. ．Thomas:ISIJ Int,2003．43．271-291．</p><p>　　4．A．W．Cramb:in ‘Impurities in engineered materials:i

97、mpact,reliability and control’ ,(ed ,C．L．Briant) ．49-89:1999．New York,Marcel Dckker．</p><p>　　5．Q．Zheng,Z．Chen and L．Zhu Proc 13th CSM Annu ．Steelmaking Conf ． Kunming,China2004 , Chinese Society for Metals．

98、</p><p>　　6．K．Larsen and R．J．Fruehan:Iron Steelmaker(ISS Trans),1991．12,125-132．</p><p>　　7．K．Sasai and Y．Mizukami: ISIJ Int．2000．40．40-47．</p><p>　　8．N．Bannenberg and K．Harste:Rev