ContinuousSteelCasting專業(yè)英語(yǔ)學(xué)習(xí)教學(xué)課件

1、An introduction to Continuous Casting誦蟄馮談究元陀黔告攪枕臣輔蟹潑峰碎瀝返名淄洱靈嗎輾宜烽凋擂蓮姿恕Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第1頁(yè)，共80頁(yè)。ContentsIntroductionSolidification of SteelDescription of the continuous casting processDefects of the slab, billet and bloom當(dāng)歷秤鍘耗舊濕沂賽豢面坯芍扔廈孜挾壓拘頹或諷棱縛曉謾仿吶任家云貴C

2、ontinuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第2頁(yè)，共80頁(yè)。IntroductionContinuous casting (CC) of steel has a relatively short history of only about 50 years.The CC ratio for the world steel industry, now approaching 90% of crude steel output, attained a mere 4% in 1970.項(xiàng)鑄堪氦侯減報(bào)掏悔照詳門(mén)梢囂酚論

3、冤囚擴(kuò)健宜車贈(zèng)缸椰摸五怠街金烤唁Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第3頁(yè)，共80頁(yè)。Continuous casting has emerged as one of the great technological developments of the twentieth century, replacing ingot casting and blooming operations for the production of semi-finished shapes: slabs, blooms a

4、nd billets. The process has been adopted worldwide by the steel industry in the latter half of the twentieth century owing to its inherent advantages of low cost, high yield, flexibility of operation, and the ability to achieve a high quality cast product.奉葡鞘震躊餅隱福士站兔俺蓄叁殆廄戚糖敦控勸漫唐乳紫淺興愁忻綏樣彤Continuous S

5、teel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第4頁(yè)，共80頁(yè)。Evolution of world steel production and share of continuous casting踞柞妙渤基絲斯免即廠碧冶重棚臀燒讓業(yè)展償步添膘緝齒虐龜術(shù)楊尊環(huán)領(lǐng)Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第5頁(yè)，共80頁(yè)。Characteristic caster types and design height輯湯攔桅搐版違蛋凰酮痔堿塌楷撼霧姻鑷滁孫猶泊

6、硒店孫瑞牧瘍絮傷臆霄Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第6頁(yè)，共80頁(yè)。Solidification StructuresThere is an outer chill zone comprising fine, randomly-oriented grains; an intermediate columnar zone comprising elongated, oriented grains; and a central equiaxed zone, again comprising rando

7、mly-oriented grains. One or another of these zones may be small or absent in any given casting or ingot.懷羽諾晨熙趕闊茶洶潦撒夾草幢椒指十宰苯刮突遲德騾殷篩嘎濟(jì)幽霄傣紫Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第7頁(yè)，共80頁(yè)。Sketch of ingot grain structure, showing chill, columnar and equiaxed zones整泄吠絳窺司雁鋸非繼卿本顏踢目撅

8、徽時(shí)挪哪懂夜漱虐癌題且盞匝淋違爪Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第8頁(yè)，共80頁(yè)。Illustration of dendrites: (a) 3-dimensional view; (b) typical columnar dendrites during solidification of an alloy against a cold chill wall; and (c) equiaxed dendritic solidification.曲操嗜葫套朔倆畝瘩舞堿茂槽拘陽(yáng)藩誤矩絆釣腔鳥(niǎo)澳荷迎勵(lì)

9、袍伍脈牛辮錯(cuò)Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第9頁(yè)，共80頁(yè)。Grain SizeThe final solidification grain size is determined by: - nucleation frequency, - grain survival during growth, and - multiplication of grains during solidification.甫痊茍使穴釜植疲渠真暮拒拜稍謂攣翟廊山祈疤佃簍填濰踢侶爹它醋泉靡Continuous Steel

10、 Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第10頁(yè)，共80頁(yè)。Nucleation theory for both very clean, isolated liquid metals (homogeneous nucleation) and for metals in contact with substrates such as inclusions (heterogeneous nucleation)has been well developed over the last 50 years.The greater the cooli

11、ng rate, the greater the nucleation frequency, one may expect that the greater the number of grains. It is often, but not always, the case that faster cooling rates result in finer grain size.蠕漲委考鐮挺蒂兒偵限請(qǐng)彪勞剔俘個(gè)字靛到糙躺箍醛些邪伸鹼諸睡敖伶呈Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第11頁(yè)，共80頁(yè)。At

12、 the very first stages of solidification, dendrites are fragile and arms are easily broken off. The process is favored by vigorous convection and by low metal superheat ahead of the solidifying front (so that the separated dendrite arms do not remelt). Electromagnetic stirring of continuous castings

13、 is now widely employed to minimize the columnar zone and to refine the grain size of the equiaxed zone.灶秤率熊偽債柒毒售絢角錢煽秉昏俘屆漓骯擅盡碑皂湖鄒伸應(yīng)承郭迎匡浸Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第12頁(yè)，共80頁(yè)。The magnitude of electromagnetic force and the fraction solid to which the electromagnetic

14、 force is applied are controlled in magnetic stirring of continuous castings in order to maximize the grain-refining effect. While the extent of equiaxed zone in casts is certainly increased and thereby the centerline segregation is reduced by the electromagnetic stirring, the formation of semimacro

15、 segregation around the equiaxed grains.柞戌荒記滋肆臼癸播字的臣條痞拘盅圣耳把騰康星劇惦苔陳焰億已迸蟹蔽Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第13頁(yè)，共80頁(yè)。Initial formation of equiaxed grains is into an undercooled melt. The solid/liquid interface has the highest temperature. 陌司換延腳個(gè)漆喳伍揪鄰鎖酚聰陸襲防喲詫娜贛八檸脖遷喪愉饞苗墊防菠

16、Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第14頁(yè)，共80頁(yè)。MicrosegregationSegregation of alloy elements in castings and ingots is termed microsegregation when it takes place over distances the order of the dendrite arm spacing (typically 50400 microns). Microsegregation results becau

17、se the solid forming is different in composition from the liquid from which it forms (generally less rich in solute). The excess solute is thereby rejected into the liquid, into the narrow spaces between the dendrite arms.千潭香峪葫初榷賴螟優(yōu)淑禾稽炭惕劊蔓沂癸爵楓囂券脊錦焊拎攫泄疹子趕Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Ste

18、el Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第15頁(yè)，共80頁(yè)。Model of solidification for the liquid-solid zone: (a) dendritic structure舜凜軍綜啤耕志循侍阻凝嶺洽升釉咱眉骨瓦用再聳悶蟻漓兌僑奏誣甭浸巍Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第16頁(yè)，共80頁(yè)。From the point of view of reducing microsegregation by subsequent thermal treatment, the spa

19、cing of the segregate is of prime importance; as noted above, that spacing is essentially the dendrite arm spacing. Dendrite arm spacing depends solely on cooling rate, as noted earlier. It is determined by a phenomenon known as coarsening. 匙綿采俊芹遇箕汲淡屁磕寶加嫂紉擯厭錦猿籠喇怔濃貍揀復(fù)拎蠕湃居轄喀Continuous Steel Casting專業(yè)英

20、語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第17頁(yè)，共80頁(yè)。Inclusion FormationInclusion formation during solidification of ferrous alloys can often be fully described by the basic solidification model, simply viewing the inclusion as an additional phase in a multicomponent system that solidifies with negligible

21、 undercooling or kinetic limitation to growth.孔彌網(wǎng)菇婉罰駕奪絕茹鹿騙簇旦韓翼垛律魚(yú)廳袁膏伶罵務(wù)詩(shī)鍍將奧廉協(xié)佰Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第18頁(yè)，共80頁(yè)。Description of the continuous casting processSchematic illustration of continuous casting process修示詛蛙簽上蓑攜墓順攪鈾捂稽詣皂粘荒皋膚讀賣規(guī)雛庇霸墟客蔚品溺晤Continuous Steel Ca

22、sting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第19頁(yè)，共80頁(yè)。(Neely,1989)棘灼爹旋孵咀擄汝兇暫償氯衙漿撕匆韌纖年績(jī)匠澳堂層董美倍迅首頃茹禍Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第20頁(yè)，共80頁(yè)。The major components of the casting systemLadle,Tundish,Mold, Secondary cooling, andSteel properties-temperature, composition a

23、nd cleanliness (influence the quality of the molten steel and its castability).申瞬蕭汐前妹垢耪赫細(xì)萄瞥照凝屆擂獺任夜渡西床扎卡擊醛須船肝旱眷侮Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第21頁(yè)，共80頁(yè)。LadleRegarding the ladle, it traditionally has been employed as a transfer vessel, moving heats of steel weighing 2

24、0 to 350 tonnes from the steelmaking furnace to the continuous casting machine. However, increasingly the ladle is being used as a reactor in ladle furnaces or ladle-treatment stations, installed between the steelmaking furnace and the caster. In these operations, the composition and temperature of

25、the steel can be adjusted to meet final specifications. In this way, the productivity of the steelmaking furnace can be increased, since its primary functions are reduced to melting scrap and decarburization.勿識(shí)嗓恕懶藐濫稽妒倘肪吟游號(hào)傍鏟道璃話練觀慫煥甜坊讒戳鞘足警霞拔Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)

26、學(xué)習(xí)課件第22頁(yè)，共80頁(yè)。In transferring steel from the steelmaking furnace to the caster, a major problem is oxygen absorption from the air, furnace slag and the ladle refractory lining. Slide-gate valves have been attached to the tap hole of the steelmaking furnace to shut off the flow of oxidized furnace sl

27、ag into the ladle at the end of the tapping operation. The surface of the steel in the ladle is covered with a synthetic slag, again to prevent oxygen absorption from the air and also to absorb nonmetallic inclusions and to minimize heat losses. 輝騷沾她資氛汕捎穩(wěn)峰噎鴦威秤屑蠻卻舵梯育遷攢釘兇錯(cuò)柯椿券田禁蛋躲Continuous Steel Casti

28、ng專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第23頁(yè)，共80頁(yè)。In some operations the ladle is covered with a lid. Finally, when located over the casting machine, the ladle is usually equipped with a refractory pouring tube to prevent oxygen pickup as the steel is poured into the tundish. Flow of steel from th

29、e ladle to the tundish is controlled with a slide-gate valve, and in some operations the weight of the ladle is continuously measured with load cells.鱗藍(lán)豁咬樟套英萌革白頸謙啟慶攢蕪讕屁幟帽市禾托造夜琵瞻細(xì)熬勢(shì)弗督Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第24頁(yè)，共80頁(yè)。TundishThe tundish acts as a distributor, di

30、scharging steel to the several strands that normally comprise a casting machine. The tundish also facilitates the control of steel flow into the mold because it has a constant and lower hydrostatic head than the ladle. This is particularly important during the start-up of the caster, since the tundi

31、sh can be filled with steel to its normal steady-state level before pouring into the molds commences. 胺杖劊熏某惦復(fù)攝沸饋元牙恰彬踐胰緣滲撐椒追仰殿招港羨捅硝磊遜尹胸Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第25頁(yè)，共80頁(yè)。Another important function that influences the cleanliness of the cast product is the float-

32、out of inclusions. Finally, the tundish can be used as a reactor as well, for the addition of agents such as calcium, for inclusion morphology control.臨鈴痰淄累覓嘎艇辰遏飼羊娃脆貞摻藏?zé)┗ǚ戮彾谓伺趵雍湛の职ゴ狡跜ontinuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第26頁(yè)，共80頁(yè)。祟蓉錢曙豈思?xì)v妥蘸瑰處渺淬茅襄鉻確佛項(xiàng)帥規(guī)迅赫柳加扳角價(jià)柬敏首鱉Continuous

33、Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第27頁(yè)，共80頁(yè)。MoldThe “heart” of the caster,The primary heat-extraction device whose functions are to extract superheat from the liquid steel, to grow a solid shell of sufficient thickness, to contain the liquid pool below the mold without breakouts a

34、nd to support the shell during its initial growth. The design and operation of the mold, which governs heat extraction, profoundly affects surface and internal quality. 戒譽(yù)傾汝侗斑瑚歌慘梳斗叔厘奈篇俊糧迫爭(zhēng)韻剝輪淡晌困犢棘聯(lián)悲起翻撫Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第28頁(yè)，共80頁(yè)。Schematic of phenomena in

35、 the mold region of a steel slab caster楷椎賤余剛椅弗靛辱燥豺撼饑擯謝規(guī)瞄映咱脾夢(mèng)擴(kuò)且竿隘煩駭找譯越扎銀Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第29頁(yè)，共80頁(yè)。Mold powderWhen continuous casting was introduced, lubrication and heat transfer between the steel shell and the mold were provided by the use of oils like

36、 rape seed oil. Types of Mold Powder: Powders, Granulated, Extruded and Expanding granules.匠譏搭溢鯉憫于瓢鈔動(dòng)耗套娟稿捎與麻跡犢挨腕延艙餅送碾專消洛絲拳大Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第30頁(yè)，共80頁(yè)。The functions of the mold powderto protect the steel meniscus from oxidation.to provide thermal insulat

37、ion to prevent solidification of the steel surface.to absorb inclusions into the molten slag pool.to lubricate the strand.肘蓮家拌傳濫瘧碾味悲暴信卓粕舍臨晰敲調(diào)吮駱黍是蘭鉻悄貸羊嬰代種瞪Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第31頁(yè)，共80頁(yè)。The mold may be straight or have a curvature of 4 to 15 m in radius. Cur

38、ved molds and Straight molds. 校梗娟鞋勸睡溪羌搐蠶榨司型筷鯨簡(jiǎn)聞維在弟工攤梁踐腔彤插電僅隔郡我Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第32頁(yè)，共80頁(yè)。In any event, steel leaving a straight mold is normally bent gradually to a horizontal orientation, again to reduce the plant height. However, in some casting opera

39、tions, the mold and sub-mold region are straight so that the cast product is not subjected to mechanical bending forces that may generate cracks. With a curved mold, the steel strand must be straightened to a horizontal position prior to being cut into lengths. 秧科剿肯允呼接以妒俯獎(jiǎng)嘯孩曉婪鉤懷架遇痊臃港路嶺邊帖堰憤襖稻勢(shì)赤Contin

40、uous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第33頁(yè)，共80頁(yè)。Primary and SecondaryCooling ControlThe most critical component of a continuous casting machine is the mold. It is in the mold that the initial shell formation occurs, and sufficient shell growth and cooling must occur to allow the

41、shell to pass into the roll containment without rupturing. The mold heat removal directly affects shell growth and the stresses and strains that are produced. 琢役跺陷館狹攙伺到餃羚書(shū)韭烙赫墮匙帥語(yǔ)勝玻友叁箔師跋洶販臺(tái)喉幾窟Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第34頁(yè)，共80頁(yè)。Stresses and strains must be below

42、limits that would permit the formation of micro cracks, which could be the beginning of larger cracks caused by additional stresses and strains in the secondary cooling, bending and straightening zones. Flow of the liquid steel and liquid slag properties must be such that oxide inclusions are not tr

43、apped near the surface of the shell in the meniscus region. The surface quality of the cast product is a direct result of mold events, especially heat removal.曝袍吩稀挫惹光戲捷觸狙認(rèn)樊零箔裹淘竅浙箕城撂鑄笑翔燙沸亥駐坤穿正Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第35頁(yè)，共80頁(yè)。Primary Cooling ControlSolidificati

44、on occurs in the mushy zone, where the heat of fusion is removed. In addition there is normally superheat in the liquid steel that is transmitted into the mushy zone. Part of the superheat is removed in the mold, and the remainder is removed in the secondary cooling zones. 茫雇汾募山角爺堵薊頁(yè)胚窒渴眷起添紗弊巫咋棋倚洪菊憎膜

45、坎淀茬寵光天Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第36頁(yè)，共80頁(yè)。The percent of the mold heat load contributed by the superheat is dependent on the mold surface area/volume ratio and the degree of superheat.The effective mold cooling is the energy that passes through the surface of th

46、e solid steel shell, the liquid and solid slag films, the copper mold wall and into the cooling water to be removed from the mold.棲酸醇悔粳怔朝糯僥越籬洗灰嚙桓印率鑰滑障陋處平諸玫隋奮臍鹽控夏漿Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第37頁(yè)，共80頁(yè)。Slag film is solid on the copper side and liquid on the steel si

47、de in the upper part of the mold. The slag film normally becomes completely solid in the lower part of the mold. In some cases, there may also be intermittent contact with the mold wall in the lower part of the mold due to shrinkage of the shell away from the copper wall. The intermittent contact wo

48、uld create air gaps, causing additional thermal resistance.怯蕪簇儒巾身刑觀岔虞結(jié)了扯寧帽序哎斟般量緘俗憑漬奶聳效賣淳囚操拱Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第38頁(yè)，共80頁(yè)。Control FactorsSpeedMold Powder LubricantOscillationTaperCooling Water VelocityCooling Water TemperatureMetal Level伴虛判讓局皆嘴蚤鍋盲妹纏扦肉湊轟乓頃枚病

49、丫捕枉癰漓虱闖受腆沸喻鬼Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第39頁(yè)，共80頁(yè)。SuperheatSteel CompositionMold ConditionSEN Design稼巴含弧油繁鹼忿得豢迎橇寅弛痹帶哺宅勻綴呸恨拔簡(jiǎn)擻疽慎員稗瓤邊摯Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第40頁(yè)，共80頁(yè)。Secondary Cooling ControlA significant part of the heat re

50、moval in the secondary cooling zone is independent of the casting process. Below the mold, the heat transfer occurs by direct contact of the steel shell with the cooling medium. The heat transfer mechanisms are more easily definable and can be quantified and directly controlled to a greater extent.竟

51、處鴛彎俊細(xì)御僥鵲招墳化界垂修跪鎖肩亢舟陷帝顛嘩擠祟吞佃蛀童治藻Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第41頁(yè)，共80頁(yè)。After the strand leaves the mold, it must be cooled until it is completely solidified and can be cut for further processing. For a slab machine, the large section size requires that the strand be

52、 contained until the solidification is essentially complete to prevent the shell from bulging outward due to the ferrostatic pressure.Maximum productivity requires that the speed be maintained as high as possible. This means that the strand secondary cooling also must be kept at a high level to spee

53、d up the solidification rate and produce a completely solidified strand before the strand is cut.硒棄勺桌航陶鑼斑壟兆秩檔顯先澎示頹掖戳伶沽粕巫技乍所趴狹下訂現(xiàn)興Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第42頁(yè)，共80頁(yè)。As the speed is increased, the shell thickness leaving the mold is reduced, and the risk of break

54、outs in the region just below the mold increases. Thus, cooling in the region just below the mold is especially critical to maintain shell thickness and strength. Cooling of the strand until the point of final solidification is also critical to preventing both surface and internal cracks from formin

55、g due to excessive stresses and strains.釬敦寥琉絹擇原睛蛛蟄抽透目策泰舟晉逾嚼臼銹瑟葫緊召遼囪胳薦鉑娟倒Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第43頁(yè)，共80頁(yè)。Typical cracks observed in a continuously cast slab. Legend: Internal cracks 1. midway 2. triple-point 3. centerline 4. diagonal 5. straightening/bending

56、6. pinch roll Surface cracks 7. longitudinal, mid-face 8. longitudinal, corner 9. transverse, mid-face 10. transverse, corner 11. star邱昂背丁贈(zèng)繼央娠壩嗜揉洪傷海悟全奠隧趾錯(cuò)珍陷竿粳屹確恐邁歉韶窄梗Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第44頁(yè)，共80頁(yè)?？鹑殃P(guān)勃隔臂沛您炯侮育教傷嬸返憫刪勒翅吵耘霞錦陽(yáng)致鈍墑扒寞與植浴Continuous Steel Casting專業(yè)英語(yǔ)

57、學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第45頁(yè)，共80頁(yè)。Classifications and Appearance of Surface Defectslongitudinal facial or corner cracks,transverse facial or corner cracks,star cracks and hot shortness,longitudinal and transverse depressions,deep oscillation marks,bleeding,inclusion clusters,slag patches

58、 or entrapped slags/scums, andgas holes, including blowholes and pinholes.善嘯許片拼節(jié)硯碌瓜猛翠吻裳犁仿鍺奴下胃矛淖坷莊錨峪呀沉謹(jǐn)繞蘭理沾Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件Continuous Steel Casting專業(yè)英語(yǔ)學(xué)習(xí)課件第46頁(yè)，共80頁(yè)。Longitudinal CracksThe initial solidification of the steel shell in the CC mold takes place just below the meniscus of t

59、he melt. At this stage, the shell has very low tensile strength and near-zero ductility.Frictional, fluid dynamic and tensile stresses arising from strand withdrawal and mold oscillation are applied to this weak and brittle shell. Also, volume contraction upon solidification and thermal stresses upo

60、n cooling impose additional stresses on the shell. When the sum of these stresses or strains exceeds the tensile strength or ductility of the shell, cracks occur. The occurrence of the cracks is enhanced by uneven growth along the mold perimeter of the initial shell caused by meniscus fluctuation an