Thick steel plate raw material manufacturing technologies can be categorized into two types: one involves special treatment of traditional thick steel ingots and continuous casting billets; the other is the development of high-quality ingots. Methods using the first approach include JFE's forging-and-rolling process and welding composite billet method, Sumitomo Metal's continuous casting large reduction method, Nippon Steel's specified compression ratio and final pass reduction method, etc. The forging-and-rolling and welding composite billet methods are particularly practical, as they can be implemented using existing equipment. However, they have the drawback of high energy consumption due to the need for two-stage material formation. The second method includes electroslag remelting technology and directional solidification technology. Steel ingots produced using these technologies have high purity, uniform composition, and dense crystalline structures. The internal non-metallic inclusions, various segregations, and common defects such as shrinkage cavities and porosity are significantly reduced compared to traditional castings, allowing thick steel plates to be produced with smaller compression ratios. Electroslag remelting technology is complex, requires specialized equipment, and involves a significant investment. In contrast, directional solidification technology is simple and less costly, but has lower material utilization rates and high auxiliary material consumption.

We will highlight several typical production methods and their characteristics below.

(1) Continuous Casting Billet Rolling Technology: The internal quality of continuous casting slabs is excellent, with low energy consumption and high yield of finished products. The rolling of ultra-thick steel plates using ordinary continuous casting billets as raw material has been a key research focus in the production of ultra-thick steel plate processes among various manufacturers in recent years. However, due to the current thickness of ultra-large continuous casting billets at home and abroad, which generally does not exceed 320mm and is up to 400mm, production of ultra-thick steel plates thicker than 150mm often faces significant challenges due to compression ratio limitations.

(2) Large Casting Steel Billet Rolling Technology: This is the traditional production process for rolling thick steel plates domestically. Although this rolling method can ensure a certain degree of compression ratio, it is accompanied by a series of issues due to the inherent defects of the casting process: Firstly, internal segregation in large casting steel billets is almost unavoidable, leading to unreliable quality; secondly, the casting process consumes a significant amount of energy and also causes certain environmental pollution; thirdly, the yield of rolled materials is low, generally not exceeding 70%.

(3) Large-scale Molded Steel Ingot Forging Technology: This is a special thick steel plate production technique that is currently widely applied both domestically and internationally. To overcome the drawback of poor internal quality in molded steel ingots, the ingots are repeatedly forged using forging presses to improve the internal quality of the steel plates. Compared to the rolling method of production, it has lower production efficiency, higher costs, lower yield, and significant product quality variation between sheets.

(4) Electroslag Remelting (ESR) Steel Slab/Directional Solidification (DS) Steel Slab Rolling Technology: Electroslag remelting technology is a new, thick plate production method that has been introduced domestically in recent years. The raw material is large billets produced by the electroslag remelting process, which boasts very high internal quality, making it suitable for producing high-quality thick plates. However, this production process is inefficient, requiring secondary melting of the billets, consuming a large amount of energy, and leading to high production costs. Abroad, there have been reports of using directional solidification steel slabs to produce large steel slabs to address segregation issues, but problems such as high energy consumption and low yield still exist.

(5) Compound Rolling Technology: This is a technology developed by Japan's JFE for producing composite metal plates. Based on this technology, two continuous casting slabs are combined into one large billet through vacuum electron beam welding, which is then rolled to produce extra-thick steel plates. This technology has now been successfully implemented domestically by Jinan Iron and Steel through independent research and development.