连铸机铸坯冷却系统优化改造研究

连铸机是当前钢铁连铸生产中的重要设备,因此连铸机生产质量对于钢材连铸质量起到了不可忽视的作用。因此新钢集团第一炼钢厂技术人员以本厂3#方坯连铸机铸坯冷却系统优化为基础,开展了连铸机设备优化研究。

钢坯冷却主要过程的作用及影响钢坯质量的因素分析

介绍了铸坯冷却过程及各环节的主要作用和影响铸坯冷却的原因,详细讨论影响铸坯质量的因素。

连铸过程中几个关键环节的设计与实现

根据连铸生产实际需要 ,对该过程中的结晶器液位控制、漏钢预报以及铸坯冷却控制等关键问题设计了一套智能化综合控制与监测系统 .在连铸生产中使用表明 ,该系统快速而准确 ,实时性能良好 ,便于实施 ,具有很高的实用价值 .

连铸后工序铸坯温度与冷却控制

在连铸产品规格大型化、品种高端化的发展形势下,连铸机除主冷却工艺(即一次冷却、二次冷却)采取的有关新技术措施外,连铸后工序的铸坯冷却(也称为三次冷却)控制技术也有了新发展。本文描述了连铸后工序的铸坯冷却工艺特点,如铸坯表面淬火技术、铸坯缓冷技术、铸坯热装轧钢加热炉技术、铸坯热送和直接轧制技术等。并就各种工艺的冶金原理、技术特点、装备特点、生产实践等方面展开了讨论。

Characteristics evolution of 6009/7050 bimetal slab prepared by direct-chill casting process

6009/7050 alloy bimetal slab was prepared by a direct-chill (DC) casting process. Homogenizing annealing, hot rolling and T6 treatment were successively performed and their effects on microstructure and properties of the slab were studied. The results reveal that the average diffusion layer thickness of as-cast slab, determined by interdiffusion of elements Zn, Cu, Mg and Si, was about 400 μm. Excellent metallurgical bonding was achieved because all tensile samples fractured on the softer 6009 alloy side after homogenizing annealing. After homogenizing annealing plus rolling, the average diffusion layer thickness decreased to 100 μm, while the network structure of 7050 alloy side transformed to dispersive nubby structure. Furthermore, subsequent T6 treatment resulted in diffusion layer thickness up to 200 μm and an obvious increase of the Vickers hardness for both 7050 and 6009 sides. The layered structure of the as-cast 6009/7050 bimetal is retained after hot rolling and T6 treatment.

Deformation and heat treatment ability of three-layer 6009/7050/6009 Al alloy clad slab prepared by direct-chill casting

Three-layer6009/7050/6009aluminum alloy clad slab was fabricated by an innovative direct-chill casting process.To study the response of the clad slab to plastic deformation and heat treatments,homogenization annealing,hot rolling,solution and aging were successively performed on the as-cast6009/7050/6009clad samples.The results revealed that excellent metallurgical bonding between7050alloy layer and6009alloy layer was achieved under optimal parameters.The clad ratio obviously decreased when the annealed sample was rolled to55%hot reduction level,and then changed slightly with further rolling.Furthermore,the content of rodlike Zn-rich phases increased significantly in7050alloy layer in the homogenized clad samples after rolling at55%,65%and75%hot reduction levels,and the higher level of hot reduction resulted in narrower diffusion layer.Subsequent solution and aging significantly improved the hardness in7050alloy layer,interfaces and6009alloy layers of the rolled samples except for the thin side for the75%hot reduction sample.

New method of direct chill casting of Al-6Si-3Cu-Mg semisolid billet by annulus electromagnetic stirring

The electromagnetic direct chill （EMDC） casting process is a welt-established production route for aluminum alloy ingot, however, the skin effect restricts the casting diameter. In order to avoid this problem, annulus electromagnetic direct chill （A-EMDC） casting process has been developed. A three-dimension finite element computational model of A-EMDC casting process was established by using ANSYS Magnetic-Nodal programs and FLOTRAN CFD programs. Microstruetures of A-EMDC casting semi-solid Al-6Si-3Cu-Mg alloy billets were investigated. Two pairs of vortexes occur within the crystallizer with opposite direction in A-EMDC. The annulus gap is advantageous to increasing circulate flow, reducing the temperature gradient as well as shallowing liquid sump depth. The microstructure obtained by A-EMDC is globular or rosette-like, and the microstructure is homogeneous in the billet.

Effect of cooling structure on thermal behavior of copper plates of slab continuous casting mold

A three-dimensional finite-element model of slab continuous casting mold was conducted to clarify the effect of cooling structure on thermal behavior of copper plates. The results show that temperature distribution of hot surface is mainly governed by cooling structure and heat-transfer conditions. For hot surface centricity, maximum surface temperature promotions are 30 ℃and 15 ℃ with thickness increments of copper plates of 5 mm and nickel layers of 1 ram, respectively. The surface temperature without nickel layers is depressed by 10 ℃ when the depth increment of water slots is 2 mm and that with nickel layers adjacent to and away from mold outlet is depressed by 7℃ and 5 ℃, respectively. The specific trend of temperature distribution of transverse sections of copper plates is nearly free of cooling structure, but temperature is changed and its law is similar to the corresponding surface temperature.

国外信息

为提高钢包滑动水口滑板的耐热冲击性及耐磨性,Hepworth耐火材料公司(HRL)开发了一种新的耐火材料——镁尖晶石。MgO滑板和镁尖晶石滑板的化学成分和物理性能见附表。

Generalized constructal optimization for the secondary cooling process of slab continuous casting based on entransy theory

Based on constructal theory and entransy theory,a generalized constructal optimization of a solidification heat transfer process of slab continuous casting for a specified total water flow rate in the secondary cooling zone was carried out.A complex function was taken as the optimization objective to perform the casting.The complex function was composed of the functions of the entransy dissipation and surface temperature gradient of the slab.The optimal water distribution at the sections of the secondary cooling zone were obtained.The effects of the total water flow rate in the secondary cooling zone,casting speed,superheat and water distribution on the generalized constructal optimizations of the secondary cooling process were analyzed.The results show that on comparing the optimization results obtained based on the optimal water distributions of the 8 sections in the secondary cooling zone with those based on the initial ones,the complex function and the functions of the entransy dissipation and surface temperature gradient after optimization decreased by 43.25%,5.90%and 80.60%,respectively.The quality and energy storage of the slab had obviously improved in this case.The complex function,composed of the functions of the entransy dissipation and surface temperature gradient of the slab,was a compromise between the internal and surface temperature gradients of the slab.Essentially,it is also the compromise between energy storage and quality of the slab.The"generalized constructal optimization"based on the minimum complex function can provide an optimal alternative scheme from the point of view of improving energy storage and quality for the parameter design and dynamic operation of the solidification heat transfer process of slab continuous casting.

Mechanism of broadening of slab in continuous casting

The mechanism of broadening of slab in continuous casting was studied by numerical simulations and experimental measurements in factories. The mechanism is derived by gradual exclusion of various factors related to the broadening of slab. It is concluded that the slab exposes to no constraint at the direction of narrow face. Because of the static pressure of molten steel, the slab deforms creepily in the direction that consequently results in the broadening of slab. The broadening of slab increases with casting speed and static pressure of molten steel. The decrease of secondary cooling intensity and strength of steel at high temperature also contribute to the broadening of slab. The micro-alloying plays an important role in improving the strength of steel and in reducing the broadening of slab.