Principle and Process of Continuous Casting Steel

Author: Chief Editor: Cai Kaiké / et al
Publisher:
Publish Date: 2002-08-01
Features:
Fragment: Statistics show that the continuous casting ratio of steel production in 26 countries and regions worldwide has exceeded 90%. The average continuous casting ratio of global steel production has increased from 33.8% in 1981 to 62.9% in 1991. In recent years, continuous casting has also been widely applied in special steel plants. It is reported that in 1991, Japan's continuous casting ratio for ordinary steel was 98.6%, and for special steel, it was 81.6%, with stainless steel continuous casting ratio close to 100%. It should be noted that from the development history of continuous casting in major steel-producing countries worldwide, the former Soviet Union started early in the research of continuous casting technology and conducted extensive research on theory, process, equipment, and product quality. Before the 1970s, it was at the forefront of the world. However, due to the dominance of open-hearth steelmaking in the former Soviet Union and the slow development of oxygen converter steelmaking, the progress of continuous casting was limited. After the 1970s, industrialized countries such as Japan, the United States, France, and Germany caught up. Especially Japan, which introduced continuous casting technology from the former Soviet Union and other countries in the late 1960s, promoted its application through emphasis on digestion and research and development. Before the 1970s, Japan primarily installed continuous casting machines in electric furnace steel plants, mainly producing small billets. In 1970, the continuous casting ratio was only 5.6%. However, the two energy crises in the 1970s accelerated the rapid development of continuous casting technology. By 1980, Japan's continuous casting ratio increased to 59.5%, and by 1991, it reached 94.4%. In 1991, the continuous casting ratios of the four largest steel companies in Japan were: Nippon Steel 98.9%, JFE Steel 98.7%, Kawasaki Steel 97.7%, and Sumitomo Metal 94.9%, achieving nearly full continuous casting. Currently, Japan's continuous casting equipment has approached saturation. The continuous casting technology in the United States was developed in cooperation with Swiss company SMS and Japanese manufacturers. Before the 1980s, its development was slow. In 1980, the continuous casting ratio was only 20.3%. After 1980, increased investment was made in continuous casting, with a focus on building large steel plants with slab,, and composite continuous casting machines. By 1991, the continuous casting ratio had risen to 75.1%. Several fully continuous casting plants also emerged. Statistics show that by 1992, over 30 large steel plants worldwide had achieved full continuous casting. It is also worth noting that in recent years, significant breakthroughs have been made in the strip casting and rolling (SCR) process, which is considered a major high-tech development in the steel industry. The traditional process for producing hot-rolled sheets involved: continuous casting slab (150–250 mm thick) → rough rolling mill (reduced to 40–70 mm) → finishing rolling mill → coil (2–10 mm). In contrast, the SCR process uses thin slab (40–70 mm) → finishing rolling mill → coil. Compared to the traditional process, this new process has a shorter production line, simplified equipment, lower investment costs, higher yield, reduced energy consumption, significantly lower production costs, and clear economic benefits. Many companies worldwide are now competing to research and develop new processes, such as Germany's SMS company's CSP (Compact Strip Production) process, Mannesmann-Demag's ISP (Inline Strip Production) process, and Italy's Danieli, Austria's Voest-Alpine, and other companies have independently developed new processes. U.S. companies Nucor and Italy's Arvedi have already built complete production lines using this new technology and achieved excellent results. It is expected that new types of steel plants incorporating melt reduction, ultra-high-power electric furnaces (DC arc furnaces), ladle refining, thin slab casting, and compact hot rolling mills will continue to emerge worldwide.
1.1.2 Development of Continuous Casting Technology in China
China began experimental research on continuous casting in 1957. In 1958, a vertical two-strand continuous casting machine was built at Chongqing Iron and Steel No. 3 Plant to cast 175×200 mm billets, becoming the first to use a 500-ton flying shear for billet cutting. In 1960, a 140×140 mm square billet vertical continuous casting machine was built at Tangshan Iron and Steel Plant. On June 24, 1964, an arc-shaped slab and square billet dual-purpose continuous casting machine was completed at Chongqing Iron and Steel No. 3 Plant, one of the earliest arc-shaped continuous casting machines used in industrial production. It was the first to use a 1,500-ton pendulum shear for billet cutting. In 1967, a 10-meter-radius arc-shaped continuous casting machine was built at Chongqing Iron and Steel, one of the largest at the time. It could cast 250–300×1500–2100 mm slabs and 3-strand 300 mm or 4-strand 250 mm. The above four continuous casting machines are still in normal production.