Defect healing in the axial zone of continuous-cast billet

Minimization of the metal consumption in components imposes ever-increasing structural requirements on steel. Accordingly, it is important to study the behavior of structural defects in continuous-cast billet (shrinkage pores, gas bubbles, axial porosity) during deformation. The use of laminar physical models to study the pressure treatment of metals is further developed in the present work. The influence of the strain on defect healing may be assessed by using laminar models together with defect application to the surface of layer n and the analysis of information regarding its distortion. The proposed method is applied to the deformation of continuous- cast bar billet in the first three rectangular grooves of the reduction cell in the 500/370 linear rolling mill at PAO Donetskii Metalloprokatnyi Zavod. On the basis of the experimental data, the existing healing mechanism for axial metal defects may be refined in terms of the total extension and the applied deforming forces.     

Distortion of the depression on the rear of the blank in broaching

When using continuous-cast billet in pipe rolling, it is expedient to roll the billet prior to broaching, so as to improve the structure and properties of the steel. To that end, a three-high screw-rolling mill for billet reduction has been installed at the TPA-80 pipe-rolling unit at OAO Sinarskii Trubnyi Zavod. Introduction of the new process was associated with increase in the rejection rate on account of indentations in the pipe. These indentations may be attributed to the depression formed at the rear of the billet in reduction and the subsequent formation of metallic semicircles on broaching; the semicircles break away and enter the deformation zone. The sources of the indentations on the rolled pipe are investigated. The broaching of the billet on a screw rolling mill is mathematically simulated. Recommendations are made with a view to reducing the surface defects on pipe produced by the TPA-80 unit with a reduction mill.     

Hot plasticity of microalloyed pipe steel in continuous casting and hot rolling

The influence of continuous casting and hot rolling (on a broad-strip 2000 mill) on the hot plasticity of microalloyed pipe steel (strength category X42) is investigated. A Gleeble 3800 system is used for physical modeling of the hot plastic deformation. The temperature intervals corresponding to loss of plasticity are determined in different conditions of slab cooling during continuous casting. In subsequent rolling, the loss of plasticity typical of cooling in the continuous-casting machine is not seen, and the steel is highly plastic.     

Cyclic-deformation system for the reduction of continuous-cast slabs

Introducing systems capable of profound reduction in a casting and rolling module improves the product quality, on account of the intense working of large continuous-cast slabs over the whole cross section and the production of uniform fine-grain structure of the metal, and also increases the cross section of continuous- cast billet. Analysis of the formation of nonmetallic inclusions and segregation in the axial zone of the thick rolled sheet is followed by analysis of the nonuniform deformation over the slag height in the reduction of large continuous-cast slabs at the 5000 mill at OAO Magnitogorskii Metallurgicheskii Kombinat. The structure of a cyclic-deformation system for preliminary deformation of large continuous-cast slabs is described, and its capabilities are explored. Hammers for preliminary deformation of large continuous-cast slabs are considered. Experimental data are presented for the deformation of continuous-cast steel 45 and 12Kh18N10T steel billet. The structure of the continuous-cast billet is assessed in the course of reduction on the cyclic-deformation system. The basic parameters of the system for preliminary deformation of large continuous- cast slabs are determined. The capabilities of the cyclic-deformation system are outlined in terms of increase in sheet quality. On that basis, the use of the cyclic-deformation system in the continuous-casting line for preliminary reduction of large continuous-cast slabs is recommended: it permits matching of the speed of continuous-casting and cyclic-deformation processes; and ensures 45–90% reduction in a single pass so as to obtain well-worked cast structure over the whole slab cross section. When using the cyclic-deformation system in the continuous-casting line, the continuous-cast slabs are reduced by means of the heat of the cast metal, thereby greatly reducing the energy consumption in billet production. The cyclic-deformation system may be used with thick-sheet and broad-strip mills for preliminary single-pass reduction of the hot slab, with improvement in sheet quality and reduction in the number of passes in the mills.     

管线钢边部发纹的形成与控制

边部发纹是管线钢常见的表面缺陷之一。针对管线钢轧制时出现的边部发纹,对其产生原因和控制方法进行了一系列试验研究。结果表明,管线钢边部发纹为连铸坯侧端面薄弱位置轧制过程开裂所致。轧制过程钢板上下表面变形不均匀,下表面延展小于上表面,因此下表面发纹距钢板边部较上表面远,导致下表面发纹无法正常切除。提高连铸坯加热均匀性可以缓解钢板上下表面不均匀变形,但不能完全解决下表面发纹问题。最终通过设定展宽阶段下辊速大于上辊速,缩小上下表面不均匀变形,控制钢板上表面发纹距边部15 mm以内,钢板下表面发纹距边部25 mm以内,上下表面发纹通过切边均可正常切除。管线钢的生产效率和成材率得到大幅提高。     

方坯和圆坯在菱方孔中的变形分析

 为满足钢坯连轧机在生产圆坯和方坯的需要,同时提高椭圆和圆孔型的利用率,提出“椭圆 圆 菱 方”孔型系统生产方坯的方法。通过有限元模拟分析和工业试验相结合研究了圆坯和方坯在菱方孔型中的变形规律,对比了方坯进菱孔和圆坯进菱孔轧制时的变形特点。发现圆进菱轧制时轧件的变形更加均匀,轧件的头尾尺寸超差小,菱孔的磨损更加均匀。为合理利用中间圆孔型轧制方坯工艺规程的制定提供了依据。     

φ60mm毛管凹坑缺陷成因分析及对策

穿后毛管或荒管在热轧定径过程中，由于定径工序相关参数不符合工艺要求，致使毛管头部外表面纵向780mm处产生一种类似于月牙形的凹坑缺陷。通过分析凹坑缺陷的产生原因，结合现场实践，采取减小定径辊辊缝，提高装配质量，严格控制定径工序总减径率和终轧温度，定期修复定径机标高等措施，消除了毛管的凹坑缺陷，为后续变形的冷加工提供了合格的毛管，有效提高了产品一次成材率。     

Rational controlled rolling on a 5000 pipe-blank mill at reduced temperature

Effective controlled billet rolling on the OAO MMK 5000 mill permits the production of pipe for underground pipelines (diameter 1220 mm; wall thickness 22 mm) from steel of strength category X80. The slab temperature before rolling may be reduced to 1100°C, with corresponding adjustment in the rolling energy and with the required solubility of carbonitrides of the microcomponents, so as to ensure the required strength.     

One-zone rolling of composite materials

The energy–force parameters of free rolling of a strip without its tension and rolling with one backward or forward creep zone in the deformation zone are compared. The limiting backward or forward tensions are determined, and the change in the linear sizes of a composite billet during deformation in a rolling mill is considered.     

60 kg/m钢轨热轧过程的三维有限元模拟

采用非线性有限元软件MARC/AutoForge，通过三维弹塑性热力耦合的有限元方法模拟了重轨800-I孔的变形过程，分析了轧件上等效应力、应变场、温度场和轧制力。轧件最大变形值于帽形腰腿圆弧和两侧腿尖处，在轧件中部靠近表面区域升温最大。     

Pipe rolling on a short mandrel with kinematic tension

Improvement in pipe production on a longitudinal rolling mill is proposed. The tandem longitudinal pipe rolling mill in the pipe-mill aggregate (PMA)-140 at PJSC (public joint-stock company) Sinarsky Pipe Works is considered. Currently, pipe is produced both from rolled billet (diameter 120 mm) and from continuous-cast billet. To reduce costs, it would make sense to discontinue the use of rolled billet and to produce all of the pipe from continuous-cast billet in the existing PMA-140. In order to employ continuous-cast billet, more profound reduction in the tandem mill is necessary. At present, the reduction is 1.16–1.5 in longitudinal rolling mill 1 and 1.07–1.15 in longitudinal rolling mill 2. With greater reduction, longitudinal guide marks may appear on the pipe surface. A possible approach to decreasing the pipe wall thickening in the groove taper and hence reducing the rejection rate due to longitudinal guide marks is to employ kinematic tension in rolling an oval sleeve on a short mandrel. The influence of the kinematic tension on the pipe shaping in grooves during longitudinal rolling of an oval sleeve is investigated. This method is found to diminish the thickening of the sleeve wall in the groove taper in longitudinal rolling mill 1. That lowers the likelihood of longitudinal guide marks on the pipe’s internal surface. The possibility of increasing the reduction in rolling on an automatic tandem mill is confirmed.     

浅析三辊开坯轧机实现大压下、大延伸的方法

为提高三辊开坯轧机的轧制能力 ,莱钢锻压厂对传统的开坯工艺进行改造 ,将六角—方孔型与箱形孔良好衔接 ,并设计了能够共轭轧制的大延伸六角孔 ,从而实现了开坯轧制大压下、大延伸 ,以及成品单出与自动咬入 ,提高了轧制节奏。     

Producing Structural-Steel Bar from Continuous-Cast Billet

The expanded use of continuous-cast billet in the production of structural-steel bar is considered. The quality of 135 × 135 mm continuous-cast billet produced on a standard continuous-casting machine and the bar derived from it is evaluated. At more recently built plants, the production of quality bar from continuous- cast billet requires total extension of the order of 6–7. On the basis of the analysis developed in the present work, it is possible to determine the maximum critical bar cross section such that the required properties are ensured.     

连铸薄板坯的质量

分析了薄板坯连铸的凝固机理，对薄板坯连铸时容易出现的缺陷和影响因素进行了讨论。     

DEFORMATION DURING HOT ROLLING OF IRON POWDER COMPACTS

Abstract

Iron powder was compacted at three different pressures and heated to two temperatures, 900° and 1000°C, for 20 min before hot rolling. Metallographic examination indicated three stages in the deformation process of hot rolling. These were: restacking and rearrangement of particles during entry into the mill, followed by localized deformation and folding-over of the particles, and finally bulk deformation leading to elongation and recrystallization of the grain structure.     

转炉坯轧制建筑结构用无缝钢管工艺研究

针对转炉连铸坯轧制建筑结构用无缝钢管的炼钢工艺及轧管工艺进行了研究;根据建筑结构用管各钢种的机械性能要求,制定了相应的控冷、控轧的工艺,实现了转炉坯轧制建筑结构用无缝钢管的大批量生产。     

保温罩对热轧中间坯温度的影响分析

针对保温罩投入使用后精轧区域中间坯头尾温差扩大以及带钢氧化铁皮缺陷增多等问题进行了分析。结果表明,保温罩投入使用后,中间坯温度升高,精轧机需要通过降低轧制速度来命中终轧温度,导致精轧轧制时间延长,是造成上述问题的主要原因。借助有限元模拟中间坯温度变化情况,根据模拟结果优化加热工艺,解决了上述问题,同时实现了节能降耗,提升了精轧轧制稳定性。     

Analysis of rolling load generated by pair crossed rolling mill

Abstract

Although a pair crossed rolling mill has a very high control capability of strip crown, a frictional force always occurs in the strip width direction between the strip and the work rolls. An analysis of rolling load was carried out, considering the shear deformation of strip cross-section caused by the frictional force. From the examination of the calculated results for a large-scale mill for production, the following conclusions were obtained: (a) the cross angle hardly influences the rolling force and torque, (b) the thrust force on the roll induced by the frictional force decreases as a result of shear deformation, (c) the thrust factor, i.e. the thrust force divided by the rolling force, is little influenced by the strip deformation resistance and the friction coefficient between the work rolls and the strip during hot rolling, (d) the thrust force applied to the rolls during hot rolling is 3–6% of the rolling force for the cross angle of 1° and this is not an obstacle related to the design of rolling mills.     

无键联接过盈量的合理选择及应用

三辊轧机安全接手法兰 (二 )与主减速机低速齿轮轴采用的是无键联接装配。为了实现二者的有效联接 ,对三辊轧机安全接手法兰 (二 )的受力进行了分析 ,并合理选择二者的装配过盈量 ,以最大可能地减少或者消除法兰 (二 )在低速轴上的转动角度 ,在包容件不发生塑性变形的情况下 ,实现了二者的有效配合     

热轧钢坯加热中的逆问题

提出为保证热轧钢坯进入轧机前温度分布符合工艺要求，需要建立出炉钢坯输送过程传热数学模型，经计算获得出炉钢坯应有的温度分布。将理论计算结果与炉内局部强化加热的供热方法相结合，使钢坯进轧机的温度分布均匀性有明显的改善，满足了工艺的要求，提高了产品轧制质量。