小方坯连铸结晶器锥度优化设计

随着连铸技术的进步和对产品质量要求的提高,结晶器锥度的优化设计已被越来越多的学者和生产者所关注。采用有限元方法对150 mm×150 mm方坯连铸结晶器铜管的锥度进行了优化,首先建立二维非稳态热力耦合模型,模拟计算铸坯在结晶器中的凝固收缩;通过建立三维的结晶器热力耦合模型,计算出结晶器铜管的变形,并在此基础上设计了结晶器的最佳锥度。结果表明,对于150 mm×150 mm方坯,在拉速为2.50 m/min时,应采用三锥度结晶器,并且结晶器铜管的锥度设计必须考虑铸坯的收缩和铜管的变形。     

方坯结晶器铜管三维温度场与热应力的分析

在对小方坯结晶器钢管内热流传递理论的基础上,研究了钢坯及结晶器内温度的传递规律。利用有限元法对结晶器钢管的温度场及热应力场进行了系统研究,并对不同拉速、冷却强及设计锥度的条件下铜管的温度场和热应力场进行了研究。提出了预应力结晶器设计的理论基础,提高连铸机的拉速及改善铸坯的质量,为实际生产提供了一定的理论指导。     

方坯连铸结晶器三维传热模拟

采用ANSYS有限元软件,以方坯连铸结晶器为研究对象,基于节点温度传递方法、利用ANSYS接触分析技术建立方坯连铸结晶器三维瞬态传热有限元模型,分析了结晶器内铸坯和结晶器铜壁的三维温度场及结晶器内铸坯坯壳分布规律。结果表明,弯月面区域铜壁温度较低,上口接近水缝内冷却水温度;弯月面下50 mm处结晶器铜壁温度最高,达到157℃;模型计算所得结晶器铜管高温区域形状与实际生产中下线铜管高温过烧区域形状基本一致;铸坯表面偏离角部30 mm处角部影响消失,铸坯表面温度趋于一致。     

不同工艺条件下小方坯连铸结晶器内的热力学行为

角部表面纵裂和偏离角裂纹是小方坯连铸中的常见缺陷。通过建立小方坯连铸结晶器内铸坯与铜管热-力耦合有限元模型,研究了不同拉速条件下小方坯在结晶器内的热-力学行为。计算分析了拉速、钢水过热度和结晶器锥度等工艺因素对结晶器内坯壳温度分布和塑性应变的影响。结果表明,铸坯角部纵裂和偏离角裂纹容易在结晶器下部发生;提高拉速、降低钢水过热度、采用多锥度结晶器均有利于降低亚包晶钢坯壳凝固前沿偏离角区域的拉应变及其裂纹倾向。一定条件下,高拉速有利于改善结晶器区域坯壳厚度和温度的均匀性、降低亚包晶钢小方坯连铸结晶器内常见裂纹的发生倾向。     

水平连铸φ150mm钻杆钢工艺优化

采用水平连铸工艺生产φ150mm钻杆钢时,结晶器铜套前段锥度按2.46%/m、后段石墨套按0.36%/m控制;钢水吊包温度启铸炉号为1630±5℃,连浇炉号为1605±5℃;采用一步启铸工艺;铸坯出结晶器后应采用二次喷淋冷却技术;拉速宜控制在2.0～2.3m/min,以上工艺参数是φ150mm钻杆钢生产成功的关键.     

薄板坯连铸结晶器内钢水凝固传热数值模拟

为研究薄板坯连铸高拉速下结晶器内坯壳生长过程,利用ANSYS有限元模拟软件,建立了CSP薄板坯连铸结晶器内钢水凝固传热数学模型,并通过实际测量得到的凝固坯壳厚度验证了模型的合理性。对结构用钢Q235B钢种,1 500 mm×60 mm规格在结晶器内凝固过程进行了模拟,研究了不同拉速、不同结晶器冷却水量对凝固的影响。研究结果表明,随着拉速降低,坯壳厚度增加;随着结晶器水量增大,坯壳厚度增加,模拟结果与实测结果相符合,为实际生产优化工艺参数提供了理论参考。     

结晶器及振动偏移对坯壳力学因素与铸坯质量的影响

本文对连铸生产中因结晶器及振动偏移(俗称对弧不正)而发生漏钢、裂纹等情况,从力学角度在理论上进行了论证。着重于偏移对结晶器下口处坯壳力学因素的影响。得出:①偏移量Δ的增减对坯壳强度的影响很大,Δ变动0.5～0.8mm,坯壳应力的变化为1.9～3倍;②坯壳内外表面的延伸率也随偏移量之增大而增加,根据坯壳强度及延伸率要求,提出了合适的偏移量不大于0.5mm。③在一定的Δ而拉速不同时,对坯壳强度在数值上的影响不大,Δ=0.5mm,150×1050和150×280mm两种铸坯拉速增加0.6M/min,应力仅增加了9.3％和6.4％。对延伸率的影响则更小。据此提出了若适当减小偏移量,在冶金因素相同的条件下,不但拉速可略加提高而坯壳应力反可得到降低,使现有连铸机有挖潜增产之可能。此外,文内对偏移影响结晶器的寿命问题也有所论及。     

结晶器铜管的失效分析

针对结晶器铜管在生产中出现的硬度不均、表面＂桔子皮＂、脱方现象,秦皇岛首钢长白结晶器有限责任公司采用调整加热温度和保温时间的方法,保证硬度符合标准,并解决了铜管裂纹和难以加工问题;控制铜管的变形量〉15%,消除了铜管的＂桔子皮＂现象;采取时效处理使铜管不在出现脱方现象。     

φ150 mm钻杆钢水平连铸工艺优化

采用水平连铸工艺生产φ150 mm规格钻杆钢时,结晶器锥度前段铜套按2.46%／m、后段石墨套按0.36%／m控制;钢水吊包温度启铸炉号按1630.4±5℃控制,连浇炉号按1605±5℃控制;采用一步启铸工艺;铸坯出结晶器后应采用二次喷淋冷却技术;拉速宜控制在2.0～2.3 m／min范围,以上工艺参数的正确掌握是φ150 mm规格钻杆钢生产成功与否及铸坯椭圆度控制的关键.     

Ф150mm钻杆钢水平连铸工艺优化

采用水平连铸工艺生产φ150 mm规格钻杆钢时,结晶器锥度前段铜套按2.46%／m、后段石墨套按0.36%／m控制;钢水吊包温度启铸炉号按1630.4±5℃控制,连浇炉号按1605±5℃控制;采用一步启铸工艺;铸坯出结晶器后应采用二次喷淋冷却技术;拉速宜控制在2.0～2.3 m／min范围,以上工艺参数的正确掌握是φ150 mm规格钻杆钢生产成功与否及铸坯椭圆度控制的关键.     

K4169合金离心铸管工艺模拟及试制研究

采用ProCAST软件对K4169合金的离心铸造工艺进行了模拟研究。通过分析浇注速度、铸型转速、浇注温度及铸型温度对离心铸管充型及凝固行为的影响,获得了外径56 mm/内径38 mm的K4169合金离心铸管最佳制备工艺参数。在此工艺参数条件下,K4169合金离心铸管可实现连续稳定充型,离心铸管壁厚差为0.2 mm,内表面疏松比例小于3%,且柱状晶平均宽度为1.7 mm。结合模拟结果对K4169合金离心铸管进行试制,所制备的离心铸管显微组织中柱状晶占比80%,且晶粒组织细小,因而离心铸管具有优异的高温塑性。     

基于铜包铝复层圆坯水平连铸的数值模拟与试验研究

利用Fluent TM模拟软件研究芯部铝液浇注温度、拉坯速度等工艺参数对水平连铸铜/铝复层铸坯温度场、液相率及流场的影响,并进行试验验证。结果表明,芯部铝液浇注温度越高,与铜管接触的铝液温度越高,液穴深度越深,铝铜之间越易发生反应;拉坯速度越快,铝液液穴深度越深,液态铝与铜管壁接触时间越长。铝液浇注温度控制在710~730℃,拉坯速度为200mm/min时可以获得优质的铜/铝复层铸锭,模拟结果与试验结果具有较好的一致性。     

圆坯连铸结晶器锥度的优化设计

建立了φ180mm圆坯二维热应力模型。根据φ180mm圆坯的数学传热模型,结合实测的边界条件计算出不同拉速下铸坯的收缩规律;建立了结晶器二维热应力模型,计算不同拉速下结晶器的温度场和变形量,从而设计出不同拉速下φ180mm圆坯的连铸结晶器锥度。结果表明,结晶器的最优锥度为多锥度的抛物线曲线,结晶器的锥度随着拉速的升高而减小。     

热型连铸准单晶铜杆的工艺及性能

利用现有的水平连铸设备,改冷铸型为加热铸型,并在此基础上对电解铜（纯度99．95％）进行了水平连铸试验。在纯铜热型连铸过程中,当铸型出口温度为1135℃、拉铸速度为74mm／s、冷却距离为20mm时,能够拉铸出准单晶铜棒材。试验后对准单晶铜的电阻率和力学性能进行了测试分析,结果表明：与国家标准纯铜线T2M相比,准单晶铜的电阻率与国家标准相当;准单晶铜的抗拉强度与国家标准相比降低了26．6％,伸长率最大增加了76％。因此,准单晶铜具有较优异的塑性加工性能和较低电阻率,并且生产率较高。     

圆坯表面网状裂纹产生原因及控制

分析了结晶器铜管在没有划伤的情况下连铸圆坯表面网状裂纹发生的原因。指出网状裂纹一方面由于初生坯壳冷却不均引起奥氏体晶粒粗大,基体中的铜元素在奥氏体晶界富集,降低了晶界结合力,诱发晶间裂纹;另一方面,由于浇铸过程液面不稳,保护渣卷入富集在在奥氏体晶界,产生应力集中点,形成裂纹发源地。通过确保结晶器对弧对中、浸入式水口的插入深度及对中、平稳的浇铸液面及合适的保护渣等方面的措施确保了网状裂纹得到根治。     

Casting a Small-diameter Tin Wire by the OCC (Ohno Continuous Casting) Process

Abstract

Tin wires of 2 mm dia have been cast by the horizontal OCC process at speeds between 0.02 m/min and 4.2 m/min. It was found that unlike the casting of larger diameter rods, it was possible to continue casting, even if the solid-liquid interface existed outside the mould. If the mould exit temperature and the mould-cooler distance were maintained at 267°C and 2 mm respectively, the solid-liquid interface was located at the mould exit when the casting speed was 0.35 m/mln. However, when the casting speed exceeded about 1.2 m/min, the cast surface of the wire deteriorated and exhibited a matted appearance due to the formation of ridges. With a casting speed of 4.2 m/min, the solid-liquid interface location was estimated to be about 4 mm outside the mould. A calculated temperature distribution within the solidifying strand revealed that the solid-liquid interface entered the cooling water when the casting speed was 1.2 m/min. Thus, in order to obtain a cast wire with a high surface finish, the strand should be solidified outside the cooling water. Casting parameter values corresponding to the condition where the solid-liquid interface reaches the mould exit were considered to be critical co-ordinates for runout (breakout). When the solid-liquid interface is located between the mould and the cooling water, tight control of the casting process, and in particular control of the metal head, is essential in order to avoid dimensional instability and runout of the liquid metal.     

The Horizontal Ohno Continuous Casting Process: Process Variables and Their Effects on Casting Stability

Abstract

Temperature profile measurements within a heated mould have been made during continuous casting of pure tin rod of 8.5 mm dia in an attempt to obtain an understanding of the influence of process variables on the position of the solidification front. It has been established that process variables such as casting speed, mould temperature and cooling position have a sensitive effect on the position of the solidification front. It varies linearly with casting speed for a given cooling position and mould temperature. The change in position of the solidification front in turn exerts a significant effect on the surface quality of the cast strand. It has been demonstrated that the solidification front should be brought well within the mould in order to obtain good dimensional and casting stability.     

Preparation of helicopter rotor counterbalance component by means of permanent-mold casting

Copper alloy was adopted to prepare helicopter rotor counterbalance component by means of permanent-mold casting. Process parameters were determined on the basis of theory calculation and computer numerical simulation. Through controlling mould temperature, pouring temperature and speed, the defects, such as gas cavity, shrinkage porosity, cold shut, can be effectively avoided. The results show that the best process parameters for smeking are as follows： pouting temperature is 1 100 ℃, pouring time is 14 s and opened mould time is 6 min. Mixture of 90% charcoal powder and 10% fluorite were selected as covering agent and 0.01% phosphorus copper acts as oxidizer. The density of rotor counterbalance component after casting in permanent-mold is 99.91% of its theory density. Mechanical properties are as follows： σb=315 MPa, σ0.2=143 MPa, δ=25%, HB=950. The mass deviation is between -5 g and ＋5 g, the curved surface distortion is less than 0.20 mm, and the largest tolerance of sectional thickness can be controlled between -0.10 mm and ＋0.10 mm.     

Forming method of axial micro grooves inside copper heat pipe

The high-speed oil-filled ball spinning and drawing process was put forward to manufacture the axially grooved heat pipe with highly efficient heat-transfer performance, and the forming mechanism of micro-grooves inside the pipe was investigated. The key factors influencing the configurations of micro-grooves were analyzed. When the spinning depth varies between 0.4 mm and 0.5 ram, drawing speed varies from 200 mm/min to 450 mm/min, rotary speed is beyond 6 000 r/min and working temperature is less than 50 ℃, the grooved tubes are formed with high quality and efficiency. The ball spinning process uses full oil-filling method to set up the steady dynamic oil-film that reduces the drawing force and improves the surface quality of grooved copper tube.