附录Technological Investigation on the Continuous Casting of Mid-Width Thin SlabsGAN Yong, ZHANG Bai Ting, ZHANG Hui, NI Man Sen and .JI Xiu QiuABSTRACT Continuous casting of thin slabs is a key state project for 7th and 8th fiveyear plans. On the basis of foundamental works, CISRI conducted the tests of 102 heats in Lanzhou Steel Works in the period of January 1991June 1992. Three slab assortments of 50900mm, 70900mm, 70500mm were examined. In June of 1992, 412 t steel of 46 heats were cast with the efficiency of 91. 3%. This-result meets the requirement of the state in this period. The mould, heft transfer, casting technology and factors influencing slabs qualities are investigated as well.KEY WORDS: mould, continuous casting of thin slab, technological properties1. IntroductionIt is a very important new technique which has been researched and developed recently in the world to cast thin slab continuously and transfer the slab directly to rolling mill. This technique has changed the traditional technology route of strip production with obvious advantages in terms of energy saving, lowering capital investment, productive cost ,metal lose and so on, thus it is suggested that it represents the trend of development of strip production. In comparison with the tradition alone, the productive cost and capital investment of thin slab casting line is reduced by 10%20% and 15%20%respectively. This technique is not suitable for revamping existing strip production line, but is very attractive for new steel works and medium, small enterprises to produce plate and strip. According to the literature the energy consumption per ton steel of thin slab casting line is62.8 kJ less than that of traditional one. The figure is to be reduced further when slab is hot charged and rolled directly. For thin slab itself, the advantages of thin slab casting can not be realized unless the slab is hot charged and rolled direct-1y due to small thickness and large surface.The key technique of thin slab castingdirect rolling route is the thin slab casting withthree core techniques: mould, submerged nozzle and mould powder. A breakthrough in these core techniques has been made during pilot testing. In this paper, the technological performance of thin slab caster and the study on mould shape, heat transfer, casting technology, the factors effecting slab quality, in particular, surface quality is described.4. Pilot Caster and Casting TechnologyThe caster at Lanzhou Steel Works is of verticalcurved type with a radius of 2m, metallurgical length of 4390mm. There are two types of moulds: mould of variable section for slabs of 70900 (mm), 50 900 (mm), mould of constant section for slab of 70500 (mm). The vibration amplitude is 3mm with a frequency of 0300cycle/min. The liquid steel for testing was delivered from an arc furnace of 5, in nominal capacity with a heat weight of about 10t. The tundish capacity is 4t. The main equipments and devices involved in the testing were: ladle, platform, tundish , tundish car, submerged nozzle, mould, vibration device, second cooling zone, pinch rollers, turn over device, straightening, cutting device, roller conveyer, dummy bar system, motor driving system and control system. The maximum casting speed is 4m/min. Steel grades 20MnSi, 16Mn and plain carbon steel were tested.The core parts of thin slab caster, which are characteristic for the caster, arc mould and submerged nozzle. The schematic view of the funnel type mould and nozzle is shown in figure 1 and 2.From figure 1, it can be seen, that the lower part of the mould is straight and which cross section determines the slab size. The opening of upper part is widening gradually to allow nozzle to be submerged. The design of such kind of mould is based on solidification of liquid steel and deformation of shell under the external force, and the construction of thenozzle must be matched with the mould (Figure 2). The nozzle cross section is elliptical, somewhat stretched in direction of major axis, so are the lateral outlets, which are made at on incline of a=250. The nozzles with different incline angle are used for different immersion depth.5. Study and Manufacture of MouldThe design work of a mould includes: determination of the shape and size, selection of the material to be made of, estimation of cooling intensity. All above mentioned points are essential for a rational design. The mould shape and size is determined by casting technology. 1 Determination of maximum openingThe maximum opening of the mould must meet with following three requirements: (1)Enough space for submerged nozzle; The shell solidification shrinkage of 0. 8%1.0%to be considered; The incline angle of the opening10for some mould length and slab thickness (Figure1).The calculated results for different slab width are shown in figure 3. For this test, mould of 900mm in wi