薄板坯连铸连轧

薄板坯连铸连轧 薄板坯连铸连轧技术是 20 世纪 80 年代末世界钢铁工业发展的一项重大技术 , 它的开发成功是近终形浇铸技术的重大突破。按类型可分为CSP、ISP、 [3]FTSR、和CONROLL技术，但就不同类型的生产线来看，以CSP建设得最多。 CSP(Compact Strip Production)即紧凑式板带生产工艺，是由德国施罗曼.西马克(SMS)公司研究开发的薄板坯连铸连扎技术，世界上第一条CSP生产线，于1989年在美国NUCOR公司的CRAWFORDSVILLE厂建成，投产后，取得满意的生产效果和良好的经济效益，因而得到广泛应用。目前，有38台CSP连铸机在内的24条CSP生产线广泛分布在北美、南美、欧洲、亚洲、非洲等世界各地，生 [4，5]产能力达到3900万吨/年。 图1.1为CSP生产线示意图，工艺为:电炉(AD或DC)?钢包精炼炉?薄板坯连铸机?均热保温?热连轧机?层流冷却?地下卷取。该工艺设备结构简单，操作稳定，产量高。具有流程短、生产简便且稳定，产品质量好、成本低、有很强的市场竞争力等一系列突出优点。 图1.1 CSP工艺生产线 1-中间包;2-结晶器;3-切断剪;4-均热炉;5-事故剪;6-除鳞机;7-精轧机; 8-1号层流却;9-飞剪;10-生产薄规格的旋转式卷取机;11-2号层流冷却; 12-生产厚规格的常规卷取机 薄板坯连铸连轧工艺流程特点: (1) 整个工艺流程是由炼钢(电炉或转炉) -炉外精炼- 薄板坯连铸- 物流的时间节奏与温度衔接- 热连轧5 个单元工序组成, 将原来的炼钢厂和热轧厂紧凑地压缩, 有机地组合在一起。 (2) 在整个工序流程中, 炼钢炉、薄板坯连铸机和热连轧机都是刚性较强的工艺装置, 为了稳定地连续浇铸和轧制, 需匹配好各段物流。例如, 对于宽度1350,1600 mm的薄板坯, 若平均拉速为415 m/ min , 则转炉容量应在100 t以上。 low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore (3) 在薄板坯连铸连轧工艺中, 热连轧是决定规模和投资的主要因素, 充分发挥热连轧机组的能力是整个建设的要点之一。炼钢炉、炉外精炼装置、薄板坯连铸机及铸机与轧机间的缓冲、衔接装置的设计、选择应以充分发挥热连轧机组的效率为主要前提。 薄板坯连铸连轧技术应用于工业生产已有十多年时间, 生产的钢种也不断 [6]扩大, 目前能覆盖传统板带产品的75% , 其中以低碳钢为主, 也可生产低合金钢、硅钢、铁素体不锈钢、奥氏体不锈钢等。薄板坯连铸连轧还是一项正在发展的技术, 随着技术的不断完善, 产品的范围还会进一步扩大。薄板坯连铸连轧省去了传统的冷装炉工序, 属直接轧制, 可以完全发挥微合金化元素的潜在作 [7]用, 对提高产品的性能有很大影响。另外, 因坯料的减薄而产生的快速冷却和凝固的过程, 可以减少坯料内部宏观偏析的均匀分布, 而且起到细化一次晶粒的作用, 但由于坯料的减薄导致了压下率的减小,因此在性能的进一步提高上也存在着一定的困难。由于薄板坯连铸一般都采用复杂横截面的结晶器, 都是在狭窄的空间下浇钢, 给浇铸带来一定的困难, 坯料容易产生横向角裂和表面纵裂, 这是需要进一步解决的问题。总的来说, 薄板坯连铸连轧来料的尺寸精度高, 温度控制均匀, 所以产品质量好, 性能更加均匀、稳定。目前CSP工艺已经生产的品种包括:用于冷轧和涂层板的含碳量小于0.075,的低碳钢、含碳量为0.15,—0.75,的中碳钢、高强度低合金钢，主要是铝、钒微合金化的屈服强度达550MP的钢、含硅量小于2.4,的无取向硅钢、双相钢、铁素体不锈钢。 low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore , 1.5 研究背景 薄板坯连铸连轧技术于 20 世纪 80 年代末期开发成功，用于生产热轧板卷的一种全新的短流程工艺 ，它首次将连铸、温度均匀化和热轧3个工艺阶段连接在一起，实现了流程简化，紧凑，降低了能耗，节约了投资和生产场地,被国际钢铁界公认是继转炉炼钢、连续铸钢之后的又一次革命。 目前,薄板坯连铸连轧生产的产品只能覆盖板材品种的70%,80%，还有相当一部分产品，如汽车面板，超深冲板和表面质量要求高的板材，奥氏体不锈钢板，部分高碳钢板等尚处于开发试验阶段。如美国Armco公司的CONROLL工艺目前只可以生产304和409不锈钢;加拿大Algom公司的FTSR中薄板坯连铸机产品包括了汽车面板和高级家电板，实际只生产了包晶钢;北极星-BHP设计时也生产汽车板，但现在生产的品种为一般深冲钢和高强度钢板。所以对于高级品种的生产，这些生产线均处于试验阶段，尚未投入工业生产，也没有经用户使用认可的成功先例。总之，采用薄板坯连铸连轧生产高档产品还有待于生产工艺的进一步发展和成熟。 从1999 年以来，我国已有珠钢、包钢、邯钢、鞍钢(2 条) 、唐钢、马钢、涟钢、本钢、通钢、济钢、酒钢、唐山国丰等12 家企业共13 条连铸连轧生产线投入生产，年生产能力达 3900 万吨左右。生产线的总数量和总产能均占世界同类生产线的 1/3 左右 ，是连铸连轧发展速度最快的国家。2005,2006 年建成的本钢、通钢、济钢、酒钢、唐山国丰等生产线目前尚处于吸取、消化、并尽快达产阶段。其余7 条生产线则多年来围绕全流程生产工艺的稳定与优化 ，产品质量与产量的提高 ，新技术的开发与应用 ，冷轧用板性能的优化与控制等方面展开工作。经过多年的不懈努力和探索，与 4 年前相比 ，近年来我国的连铸连轧生产的发现趋势出现了一些可喜的变化。 但与先进国家相比，我国板带钢在钢材中占有率远低于发达国家，冷轧板的供给量仍不能满足人们生产生活和国家工业建设的需要，而且连铸连轧生产的薄板质量一般，不能用于汽车板等质量性能要求优良的产品，所以研究CSP工艺下冷轧板的组织性能具有重要的现实意义。另外，关于冷轧再结晶过程中的织构演变规律，虽然已经有很多的研究，但至今仍没有非常确定的理论，存在有争议。low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 本实验将采用最新的织构研究手段:XRD，研究宏观织构演变规律，不仅在冷轧再结晶织构演变规律领域中有非常重要的理论意义;同时对于当今CSP向着高附加值产品发展具有重要的实际意义。 第二相粒子 一般指的是钢的合金元素在热处理过程中形成的合金化合物粒子，常见的有碳化物、硫化物、氧化物等。 第二相粒子在钢中有很大的作用，可以与基体呈共格或者非共格关系，往往会阻碍位错的运动，使钢的强度增大，这就是第二相强化。第二相强化使刚强度增大，但对塑性是有害的。第二相粒子如TiC、NbC等还有细化晶粒的作用，在钢的生产中第二相粒子具有重要的意义。 第二相在钢中的有利作用 第二相控制基体晶粒长大 1. 晶粒细化是使钢材强度提高的同时还提高其韧性的唯一的强化机制，一直受到广泛的重视，在采用各种工艺使基体晶粒细化的同时，还必须有效防止晶粒长大才能保证晶粒细化的效果，而第二相钉扎晶界是最重要的阻止晶粒长大的方法。 2.第二相沉淀析出强化 基体中弥散分布的第二相颗粒可产生弥散强化作用，由于第二相通常是通过沉淀析出产生的，故也称为沉淀强化。第二相沉淀强化往往会导致钢材韧性的下降，但相对于位错强化及间隙固溶强化等其他强化方式而言，其脆化矢量较小，故第二相强化是除晶粒细化外应优先采用的强化方式。位错越过第二相颗粒的机制有切过机制和绕过机制，其强化机制分别为切过机制和Orowan机制，当第二相相对较软或尺寸很小时主要为切过机制，其强度增量正比于第二相的尺寸和第二相体积分数的二分之一次方，而当第二相较硬或尺寸较大时主要为Orowan机low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 制，其强度增量正比于第二相体积分数的二分之一次方并大致反比于第二相的尺寸。对每一种特定的第二相都存在一个临界尺寸dC，小于临界尺寸时切过机制起作用而大于临界尺寸时Orowan机制起作用，在临界尺寸附近可得到最大的强化效果。 3.第二相调节形变基体的再结晶和后续固态多型性相变行为 钢材经受塑性变形后，形变基体中将存在形变储能。形变储能是基体再结晶的驱动能，害可增大后续固态多型性相变的相变驱动能。当第二相在形变过程中以应变诱导析出的方式沉淀析出后，将有效钉扎位错使之不容易发生回复和再结晶，从而显著推迟再结晶的发生。大量试验结果表明，微合金碳氮化物的应变诱导沉淀一旦发生，形变奥氏体的再结晶过程就被显著推迟。应变诱导沉淀的第二相阻止形变奥氏体基体再结晶过程的同时，将使基体的形变储能得以保存，若继续进行形变，则形变储能将不断累积。形变储能可明显增大奥氏体相的自由能， 生铁素体相变时，形变储能将有效促进铁素体相的形成，使在随后冷却过程中发 铁素体相形成的温度比平衡温度A3明显升高或使确定温度下的铁素体形成量明显大于平衡形成量;同时，应变诱导析出第二相后，奥氏体基体化学成分的变化将增高奥氏体相的自由能，从而进一步促进铁素体相的形成;此外，由于形变基体中晶格畸变和扭折晶界的存在，可明显增大铁素体的非均匀形核率，使得形变诱导铁素体的晶粒尺寸明显细化且分布均匀。 4.第二相促进晶内铁素体形成 低碳钢中晶内铁素体的形成可在一定程度上增加铁素体的形核率从而细化铁素体晶粒并使铁素体晶粒的形状和分布有利，近年来受到广泛的关注。事实上，晶内铁素体的最大好处在于:晶内铁素体是在较高温度下形成的，碳含量及合金元素含量很少，因而具有非常高的韧塑性;晶内铁素体分割了原奥氏体晶粒，晶内铁素体的位向与晶界形核连续推进的铁素体晶粒的位向完全不一样，由此可明low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 显抑制了非等轴铁素体晶粒的形成及定向长大;韧性较高的晶内铁素体完全包围了第二相颗粒从而使其对钢材韧塑性和疲劳性能的损害显著降低甚至消除。 5(固定非金属元素 钢中一般均存在微量的非金属元素如碳、氮、氢等，它们以间隙固溶状态存在时，往往对钢材的某些性能造成严重的危害。如碳、氮间隙固溶原子往往会偏聚到位错线上形成气团，当材料承受冷加工变形时，气团将阻碍位错发生滑移运动，一旦解钉则将产生屈服伸长，这种不连续屈服现象将严重有效钢材的深冲性能，导致冷加工变形钢材的表面质量下降，对于表面质量要求很高的零件如轿车面板必须严格控制间隙固溶原子的存在。在不锈钢中，间隙固溶原子往往偏聚在晶界上，加工及使用过程中会与固溶的铬发生反应生成相应的化合物，导致晶界附近固溶贫铬而产生晶间腐蚀。 6.提高耐磨性 在材料表面具有适当分布的与基体组织良好结合的高硬度第二相颗粒对材料耐磨性的提高具有重要作用。从黏着磨损机理考虑，组织的连续性和性能的均一化会产生较大面积的相互接触和黏着，对耐磨性不利;而适当分布的硬质颗粒在磨损过程中逐渐凸出，若它们与基体之间结合较好而不会轻易脱落，则可明显减小摩擦副之间的真实接触面积而避免黏着。而从磨料磨损机理考虑，由于凸出的颗粒的硬度远高于基体材料硬度，而磨粒主要与凸出的颗粒之间发生相互作用，从而使磨损过程处于低磨损区而明显减轻磨损。显然，耐磨性提高越大。(东乔) 钢铁材料中第二相的有害作用 相关专题: 钢铁技术 时间:2012-04-17 19:44 【阿里巴巴冶金】 low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 钢铁材料中除基体相之外的所有相均可称为第二相。传统上曾将对钢材性能有害的相称为夹杂物，但在良好控制条件下很多传统意义的夹杂物如硫化锰、氮化铝等也可对钢材性能产生明显有利的作用，而在控制不好时很多传统意义的第二相如渗碳体、氮化钛也可能对钢材性能明显有害，因此，完全没有必要专门划分夹杂物，本文统称为第二相。 第二相在钢中具有十分重要的作用，其对钢的强度、韧性、塑性、深冲性、疲劳、磨损、断裂、腐蚀以及许多重要的物理和化学性能均具有重要的影响。 深入了解第二相在钢中的有害作用及其随第二相尺寸、形状、分布和体积分数的变化规律，将有助于控制第二相(特别是夹杂物)在的尺寸、形状、分布和体积分数从而尽量减轻或消除其有害作用。 1.第二相引发钢中微裂纹 根据钢中第二相发生断裂时的特征，一般可将第二相分为解聚型和断裂型。解聚型第二相与基体的结合力较弱，为非共格结合，形状多为近球形，受到外力时容易沿相界面与基体脱离(解聚)，从而产生尺寸略大于第二相颗粒尺寸的微裂纹。断裂型第二相一般与基体有较强的结合力，故多为半共格结合，由于错配度的各向异性，其形状多为片状或棒状;也有与基体非共格结合的但塑性很高的第二相，在高温塑性变形加工过程中被拉长而成为片状或棒状;它们受到外力时容易沿尺寸较小的方向发生断裂，形成尺寸略大于第二相颗粒短向尺寸的微裂纹。此外，与基体完全共格或仅存在很小错配度的半共格的第二相，当其尺寸在数十nm以下时，与基体的结合力较强且其形状多为球形，因而既不容易解聚也不容易发生自身断裂，即基本不会引发微裂纹，可称为非引裂第二相。微裂纹尺寸越大，在外力作用下越容易发生扩展并最终导致破断失效，根据断裂力学的相关理论，只有达到临界尺寸的微裂纹才会发生扩展而导致断裂，因此，控制最大颗粒第二相的尺寸(而不是第二相的平均尺寸)从而控制最大尺寸的微裂纹使之不超过临界裂纹尺寸对提高材料的断裂强度是至关重要的。低强度钢中的临界裂纹尺寸接近mm，只要控制不产生最大尺寸为mm数量级以上的第二相颗粒就不致发生严重的脆性断裂;而超高强度钢中的临界裂纹尺寸在10μm左右，必须严格控制10μm以上尺寸的第二相颗粒的形成。大颗粒第二相的形状对微裂纹的产生具有非常重要的影响。具有尖锐棱角的脆性第二相在尖锐棱角处将发生显著的应力集中故很容易引发微裂纹;显著拉长的膜状、薄片状、线状第二相颗粒非常容易发生折断而引发微裂纹。显然，控制第二相颗粒的形状特别是大尺寸第二相颗粒的形状具有重要的意义。 2(第二相对钢的韧性的影响 第二相颗粒周围存在较高的应力场，容易引发微裂纹;另一方面，当微裂纹扩展到第二相颗粒周围时裂纹尖端应力场将与第二相颗粒周围的应力场发生相互作用，促进裂纹扩展。因此，第二相颗粒的存在均将导致钢材韧性的下降。低碳钢中，钢材的韧性通常用韧脆转折温度来表征，而将某种强化方式每提高强度1MPa相应导致韧脆转折温度提高的度数称为脆性矢量。均匀分布的细小第二相的脆性矢量约为0.26?/MPa，是除晶粒细化外脆性矢量最低的强化方式，即均low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 匀分布的细小第二相对钢材的脆性的危害相对很小;同时，由前述第二相强化强度增量的表达式可推知，第二相对钢材韧性的损害程度将正比于体积分数的二分之一次方而大致反比于其平均尺寸。 第二相对钢的塑性的影响塑性变形的本质是材料中的可动位错大规模滑移的结果，材料的塑性可分为均匀塑性和不均匀塑性两部分。实际应用的结构材料中，对材料塑性的要求主要集中于均匀塑性，因为一旦材料的塑性变形超出了均匀变形阶段而进入集中变形(颈缩)阶段，该材料实际上已失效而不能使用。但材料的非均匀塑性对其韧性和使用安全性也有重要意义。(东乔) 第二相在钢中的有利作用 1.第二相控制基体晶粒长大 晶粒细化是使钢材强度提高的同时还提高其韧性的唯一的强化机制，一直受到广泛的重视，在采用各种工艺方法使基体晶粒细化的同时，还必须有效防止晶粒长大才能保证晶粒细化的效果，而第二相钉扎晶界是最重要的阻止晶粒长大的方法。 2.第二相沉淀析出强化 基体中弥散分布的第二相颗粒可产生弥散强化作用，由于第二相通常是通过沉淀析出产生的，故也称为沉淀强化。第二相沉淀强化往往会导致钢材韧性的下降，但相对于位错强化及间隙固溶强化等其他强化方式而言，其脆化矢量较小，故第二相强化是除晶粒细化外应优先采用的强化方式。位错越过第二相颗粒的机制有切过机制和绕过机制，其强化机制分别为切过机制和Orowan机制，当第二相相对较软或尺寸很小时主要为切过机制，其强度增量正比于第二相的尺寸和第二相体积分数的二分之一次方，而当第二相较硬或尺寸较大时主要为Orowan机制，其强度增量正比于第二相体积分数的二分之一次方并大致反比于第二相的尺寸。对每一种特定的第二相都存在一个临界尺寸dC，小于临界尺寸时切过机制起作用而大于临界尺寸时Orowan机制起作用，在临界尺寸附近可得到最大的强化效果。 3.第二相调节形变基体的再结晶和后续固态多型性相变行为 钢材经受塑性变形后，形变基体中将存在形变储能。形变储能是基体再结晶的驱动能，害可增大后续固态多型性相变的相变驱动能。当第二相在形变过程中以应变诱导析出的方式沉淀析出后，将有效钉扎位错使之不容易发生回复和再结晶，从而显著推迟再结晶的发生。大量试验结果表明，微合金碳氮化物的应变诱导沉淀一旦发生，形变奥氏体的再结晶过程就被显著推迟。应变诱导沉淀的第二相阻止形变奥氏体基体再结晶过程的同时，将使基体的形变储能得以保存，若继续进行形变，则形变储能将不断累积。形变储能可明显增大奥氏体相的自由能，在随后冷却过程中发生铁素体相变时，形变储能将有效促进铁素体相的形成，使铁素体相形成的温度比平衡温度A3明显升高或使确定温度下的铁素体形成量明显大于平衡形成量;同时，应变诱导析出第二相后，奥氏体基体化学成分的变化low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore 将增高奥氏体相的自由能，从而进一步促进铁素体相的形成;此外，由于形变基体中晶格畸变和扭折晶界的存在，可明显增大铁素体的非均匀形核率，使得形变诱导铁素体的晶粒尺寸明显细化且分布均匀。 4.第二相促进晶内铁素体形成 低碳钢中晶内铁素体的形成可在一定程度上增加铁素体的形核率从而细化铁素体晶粒并使铁素体晶粒的形状和分布有利，近年来受到广泛的关注。事实上，晶内铁素体的最大好处在于:晶内铁素体是在较高温度下形成的，碳含量及合金元素含量很少，因而具有非常高的韧塑性;晶内铁素体分割了原奥氏体晶粒，晶内铁素体的位向与晶界形核连续推进的铁素体晶粒的位向完全不一样，由此可明显抑制了非等轴铁素体晶粒的形成及定向长大;韧性较高的晶内铁素体完全包围了第二相颗粒从而使其对钢材韧塑性和疲劳性能的损害显著降低甚至消除。 5(固定非金属元素 钢中一般均存在微量的非金属元素如碳、氮、氢等，它们以间隙固溶状态存在时，往往对钢材的某些性能造成严重的危害。如碳、氮间隙固溶原子往往会偏聚到位错线上形成气团，当材料承受冷加工变形时，气团将阻碍位错发生滑移运动，一旦解钉则将产生屈服伸长，这种不连续屈服现象将严重有效钢材的深冲性能，导致冷加工变形钢材的表面质量下降，对于表面质量要求很高的零件如轿车面板必须严格控制间隙固溶原子的存在。在不锈钢中，间隙固溶原子往往偏聚在晶界上，加工及使用过程中会与固溶的铬发生反应生成相应的化合物，导致晶界附近固溶贫铬而产生晶间腐蚀。 6.提高耐磨性 在材料表面具有适当分布的与基体组织良好结合的高硬度第二相颗粒对材料耐磨性的提高具有重要作用。从黏着磨损机理考虑，组织的连续性和性能的均一化会产生较大面积的相互接触和黏着，对耐磨性不利;而适当分布的硬质颗粒在磨损过程中逐渐凸出，若它们与基体之间结合较好而不会轻易脱落，则可明显减小摩擦副之间的真实接触面积而避免黏着。而从磨料磨损机理考虑，由于凸出的颗粒的硬度远高于基体材料硬度，而磨粒主要与凸出的颗粒之间发生相互作用，从而使磨损过程处于低磨损区而明显减轻磨损。显然，耐磨性提高越大。(东乔) low rotor, until rotor of weight by steam end sliding block and Reed end rotor Bay support, in put low rotor of while should in Reed end rotor Bay at added pad sleeper, due to stator has preliminary adjustment finished, so stator within bore exists must Yang degrees, so should note adjustment makes rotor keep and stator within bore concentric, makes rotor not and coil contact. Panasonic lane hook, remove wire rope hoist, wrapped at the rotor excitation-side shoulder arc washer, and move the lifting wire rope to protect mat. Two 5T chain hoist end beam connections and welded to the rotor carriers, length adjusted for field conditions, and at the other end of the stator lifting hook or end cap end lugs connected, as shown in Figure 11.4.3-1. With Lane slightly single head upgrade rotor Reed end, keep rotor level, demolition rotor Bay or support sleepers, then slowly synchronization pull two only chain gourd, makes rotor in steam end sliding block of support Xia along arc skateboard to steam end sliding, this process in the, lane must and rotor of sliding keep synchronization, in rotor of steam end and Reed end are due hand guardianship rotor and stator Zhijian of clearance. Dang by steam end side has nursing ring protection of coil end Department into stator within bore Hou, slightly upgrade rotor Reed end, in rotor ontology following loaded into Central sliding block, its loaded into Hou must very carefully to along axis to for find are, and note observation rotor coupling in wear loaded process in the whether turned, as has should stop wear loaded, needed on Central sliding block location again for find are, while should note in Central sliding block placed yihou only allows steam end sliding block beyond stator within bore, and in Central sliding block and steam end rotor nursing ring Zhijian at least should keep must of distance ( 300MW 76mm, 1000MW is 50mm). When the steam side slider close to steam at the end of the stator bore