Mold Assembly: The “Heart of Creation” in Modern Industry and the Frontier of Technological Innovation

Cooling water flows at a speed of 6-10 meters per second through precision-designed slits only 3.5-4 mm wide, solidifying molten metal exceeding 1500°C into shape within a distance of less than one meter. This process unfolds daily in metallurgical and chemical plants worldwide.

The mold assembly is a core component in continuous steel casting equipment and chemical crystallization processes. In the metallurgical field, it is known as the “heart of the continuous caster,” responsible for solidifying high-temperature molten steel into cast billets of specific cross-sectional shapes.

In the chemical industry, crystallizers are crucial equipment for producing high-purity chemicals and functional materials, determining the particle size distribution and purity of the final products.

01 Application Fields: From Steel Metallurgy to Fine Chemicals

Mold assemblies have extensive applications in the industrial sector, primarily divided into two major directions: metallurgical continuous casting and chemical crystallization. Although the processes differ between these fields, both rely on the precise control of phase transitions provided by crystallizers or molds.

In the metallurgical industry, the mold assembly is the core equipment of the continuous casting production line. It receives molten steel from the tundish and solidifies it into a sturdy solidified shell with the designated cross-sectional shape. Its performance directly affects the dimensional accuracy, surface quality, and internal structure of the cast billet.

In the chemical field, crystallizers are key equipment for producing high-purity chemicals, pharmaceutical raw materials, and functional crystalline materials. According to statistics, the global mold assembly market is maintaining steady growth, with its size expected to continue expanding by 2031. It involves multiple application sectors, including metallurgy, chemicals, pharmaceuticals, and papermaking.

02 Core Components: Complex Systems and Precision Parts

Whether for metallurgical or chemical applications, a complete mold assembly is a highly integrated, complex system where multiple precision components work in coordination.

The main components of a metallurgical mold assembly include the mold copper tube, outer water jacket, diversion water jacket, sealing devices, and foot rollers. The mold copper tube, which directly contacts the molten metal, is responsible for rapid cooling and solidification.

These components are precision-machined and assembled to ensure exact fitting. The design of the cooling water channels directly impacts heat exchange efficiency, while the choice of wear- and corrosion-resistant materials determines the equipment’s service life.

Chemical crystallizers come in various types based on their working principles, such as the Draft Tube Baffle (DTB) crystallizer and the Forced Circulation (FC) evaporative crystallizer.

Taking the DTB crystallizer as an example, it consists of five basic components: the crystallizer vessel, bottom-mounted axial flow pump, baffle, circulation pump, and heat exchanger. The design of the baffle is particularly critical as it separates fine crystals from coarse ones, enabling precise control over crystal quantity.

03 Technological Frontiers: From Design Innovation to Intelligent Development

Mold technology is undergoing a transformation from traditional manufacturing toward intelligent and green development. The 14th Annual Conference on Industrial Crystallization Science and Engineering Technology held in 2025 clearly stated that industrial crystallization technology is moving toward “intelligent, green, and low-carbon” development.

In the metallurgical field, multi-stage mold technology represents a significant innovation. Traditional molds mostly feature foot roller structures below the mold outlet, whereas multi-stage molds install copper plates with spring compression devices on the billet surface below the mold outlet.

This design enhances support and cooling for the initial solidified shell exiting the mold. By intensifying spray cooling on the billet corners, it also reduces the risk of corner cracks and breakouts.

The independently developed continuous crystallization equipment and intelligent control system by the National Engineering Research Center of Industrial Crystallization Technology at Tianjin University mark China’s gradual reduction in reliance on imported technology in the high-end chemicals sector. The team has achieved a series of breakthrough results over more than four decades of R&D, spanning new crystallization process development and intelligent crystallization equipment design.

04 Materials and Manufacturing: Key Factors Determining Performance

The performance of a mold assembly largely depends on its material selection and manufacturing processes. The inner wall material of metallurgical molds is primarily made from copper-based alloys, including pure copper, copper-silver alloys, phosphorus deoxidized copper, copper-beryllium alloys, and chromium-zirconium-copper alloys.

The selection of these materials mainly considers their good thermal conductivity, sufficient wear resistance, mechanical strength, and hardness.

To improve wear resistance and smoothness, thereby reducing the billet withdrawal resistance, some molds have coatings applied to the copper wall surface, typically chromium plating, or nickel, tungsten, iron plating, or a three-layer plating of nickel, nickel-phosphorus alloy, and chromium.

An innovative manufacturing process involves using metal additive manufacturing (3D printing) to build solid entities, leaving several cooling channels within the steel and/or copper base plates. This integrated continuous casting mold component achieves a metallurgical bond between the steel and copper base plates, ensuring application performance and extending service life.

05 Fault Prediction: Intelligent Safety Technology

Modern mold assemblies are also equipped with advanced safety monitoring systems, particularly breakout prediction systems. Currently, there are three main monitoring methods: monitoring friction force, detecting changes in heat transfer, and measuring via copper plate thermocouples.

Among these, the copper plate thermocouple measurement method boasts relatively high accuracy. It works by installing multiple thermocouples on the mold. The temperature values from these thermocouples are transmitted to a computer system, which triggers an alarm if they exceed set limits.

This method can not only predict sticker-type breakouts but also warn against crack-related breakouts, slag inclusion breakouts, billet depression, and can intuitively display the solidification status of the solidified shell within the mold. This information can be integrated into a billet quality prediction system, enabling comprehensive process monitoring and quality control.

In a multi-stage mold, four brackets, each equipped with copper plates, are connected to the lower part of the mold shell via flanges. Each copper plate on these brackets is positioned against the face of the billet below the mold.

This design allows each copper plate to press against the billet surface during casting through force generated by springs, enhancing support while improving heat flow transfer.

From the rotating roller tables on continuous casting lines in steel plants to the precision crystallization tanks in the cleanrooms of pharmaceutical companies, these seemingly unrelated equipment share different evolutionary forms of the same core technology.

Industrial crystallization technology—this “‘chip’ for the high-quality development of new chemical materials”—is growing its own roots and branches in the soil of Chinese manufacturing.