Hot rolling technology of steel plate and strip

Traditional hot rolling technology, as the core process for sheet and strip production, has developed into a highly mature process system over a century. It possesses irreplaceable advantages in product range, thick-gauge production, and the development of high-value-added products, while simultaneously absorbing advanced concepts from short-process technologies and continuously evolving towards green and intelligent manufacturing.

Strategic Position and Technological Challenges of Traditional Hot Rolling

Core processes in the steel industry

Steel plates and strips are fundamental raw materials for modern industry, widely used in various sectors of the national economy, including automobile manufacturing, shipbuilding, oil and gas transportation, home appliance production, and construction engineering. In the entire steel production process, the hot rolling process plays a crucial role in transforming continuously cast or pre-rolled slabs into products with specific dimensions, shapes, microstructures, and properties. Statistics show that globally, hot-rolled steel accounts for over 85% of total steel production, with steel plates and strips making up more than 60% of hot-rolled products.

Traditional hot strip rolling technology is the dominant process in plate and strip steel production. Since the construction of the world’s first 1470mm wide strip hot strip rolling mill in Aslan, USA, in 1924, this technology has undergone a full century of development. Compared to traditional single-stand rolling, hot strip rolling enables continuous multi-stand operation, resulting in a geometric increase in production efficiency and a significant improvement in product quality stability. Today, a modern hot strip rolling production line can have an annual capacity of 3-6 million tons, producing products with thicknesses ranging from 0.8-25.4mm and widths exceeding 2000mm, capable of producing a wide range of high-end products from ordinary carbon structural steel to high-strength steel, pipeline steel, automotive steel, and silicon steel.

A Century of Technological Evolution

Looking back at the century-long history of hot continuous rolling technology, three important stages can be clearly identified.

The first generation of hot strip mills emerged between the 1920s and 1950s. The technological characteristics of this period included relatively small equipment sizes, with mill roll lengths ranging from 1120 to 2490 mm. Cross-rolling widening technology was used to compensate for the slab width limitation. Rolling speeds were only 10-12 m/s, with single coil weights ranging from 6 to 13.6 tons and annual production capacity of 1-2 million tons. Due to low automation levels, product quality fluctuated significantly, with the beginning and end often exhibiting tongue-like or fishtail-like shapes, and poor accuracy in thickness and width.

The second generation of hot strip mills emerged in the 1960s. In 1960, McLaurence Steel Company in the United States first used computer-controlled settings and control of the roll gap and speed of the finishing mill on its 1525mm hot strip mill, marking the beginning of the era of automation in hot strip milling. In 1961, U.S. Steel’s Great Lakes Plant first adopted speed-increasing rolling technology on its 2032mm hot strip mill, expanding the finished product thickness range to 1.5-12.7mm, with a maximum coil weight of 40 tons, and increasing annual output to 2.5-3.5 million tons. The application of micro-tension constant-weight rolling technology and automatic thickness control technology resulted in a qualitative leap in strip thickness accuracy.

The third generation of hot strip mills began leading the industry’s development in the 1970s. In 1969, the 2286mm hot strip mill at Japan’s Kimitsu plant propelled hot rolling technology towards larger scale and higher speeds. During this period, the mill’s annual output reached 6 million tons, the maximum weight of a single coil was 45 tons, the finished product thickness decreased to 0.8mm, and the rolling speed increased to 28-30m/s. The number of stands in roughing mills increased, and finishing mills generally adopted a 7-stand configuration. New technologies such as walking beam furnaces, bending roll devices, laminar flow cooling devices, and rapid roll changing devices were widely applied, and the entire production process was computer-controlled.

The contemporary challenges we face

Entering the 21st century, traditional hot rolling technology faces new challenges and opportunities. On the one hand, the rapid development of short-process technologies such as thin slab continuous casting and rolling has created a competitive advantage in the production of thin-gauge products and energy conservation and consumption reduction. On the other hand, the market demand for high-value-added products such as high-strength steel and high-grade silicon steel continues to grow, placing higher demands on the control precision and product adaptability of hot rolling technology.

Against this backdrop, traditional hot strip rolling technology must answer three key questions of our time: How to further improve product precision and quality stability? How to maintain product variety advantages while saving energy and reducing consumption? How to integrate into the wave of digitalization and intelligentization to achieve transformation and upgrading?

In-depth analysis of the principles of traditional hot continuous rolling process

Fundamentals of Physical Metallurgy: The Evolutionary Logic from Microscopic to Macroscopic

Hot rolling is essentially the plastic deformation of metal under high temperature conditions, accompanied by a complex evolution of its microstructure. To understand this process, it is necessary to examine the intrinsic relationship between “temperature-deformation-microstructure-properties” from the perspective of physical metallurgy.

Temperature is the most critical process parameter in hot rolling. When the slab exits the furnace, its temperature is typically between 1150-1250℃, at which point the steel is in a fully austenitic state. During roughing, finishing, and laminar cooling, the temperature continuously decreases, eventually completing the phase transformation at the coiling temperature (usually 500-700℃). The temperature trajectory determines the austenite recrystallization behavior, phase transformation products, and the final microstructure. Studies have shown that when the finishing rolling temperature is controlled at 850-880℃ and the coiling temperature at 620-700℃, relatively ideal comprehensive mechanical properties can be obtained.

Deformation is the direct driving force of the hot rolling process. During rolling, the enormous rolling force causes compressive deformation in the thickness direction of the slab, while simultaneously extending along the rolling direction and widening in the width direction. This plastic deformation not only changes the geometry of the product but, more importantly, introduces a large number of crystal defects into the material, providing energy conditions and nucleation sites for recrystallization and phase transformation. In the finishing rolling stage, the first four stands employ a concentrated reduction strategy, with a single-pass reduction rate reaching 40-50%, while the last three stands focus on shape control.

Microstructure serves as the bridge between processing technology and performance. The final mechanical properties of hot-rolled products depend on their microstructure, including grain size, phase composition, and precipitate distribution. Taking Q235B steel as an example, approximately 82% of the coils have a yield strength of 320-360 MPa, approximately 88.4% have a tensile strength of 450-490 MPa, and approximately 86.8% have an elongation of 27%-34%. Achieving these performance indicators relies on precise control of microstructure evolution.

Fine-grained strengthening is the most important strengthening mechanism for hot-rolled products. The smaller the finished product thickness, the higher the overall compression ratio, resulting in a microstructure with high-density dislocation and subgrain structures, increased effective grain boundary area, and promotion of phase deformation nucleation rate and grain refinement. Simultaneously, the larger surface temperature drop and faster cooling rate of thin strips also contribute to grain refinement. Quantitative analysis shows a clear inverse relationship between ferrite grain size and yield strength—the finer the grains, the higher the strength.

Core of process control: temperature field, deformation field, and interface behavior

The process control of hot rolling involves the coupling effect of multiple physical fields, among which temperature field, deformation field and interface behavior are the three most critical control dimensions.

Temperature field control is crucial throughout the entire hot rolling production process. From setting the furnace exit temperature to controlling temperature drop during roughing and finishing rolling, and designing the laminar flow cooling path, each step directly impacts the final product quality. In traditional hot continuous rolling processes, the initial rolling temperature is typically controlled at 1030-1150℃, the final rolling temperature at 850-880℃, and the coiling temperature at 620-700℃. The challenge in temperature field control lies in its dynamic and non-uniform nature—temperature differences exist between the slab surface and core, and between the beginning/end and the middle. This non-uniform temperature distribution leads to uneven deformation, affecting the consistency of slab shape and performance.

Deformation field control is primarily manifested in the formulation of the reduction schedule. The reduction schedule determines the path of slab thickness reduction, directly affecting rolling load, strip shape control, and microstructure evolution. A reasonable reduction schedule requires a balance between equipment capacity, product quality, and production efficiency. Modern hot strip finishing mills typically employ a seven-stand four-high mill configuration, achieving synergy between thickness reduction and strip shape control through optimized reduction distribution across each stand. During the finishing stage, strip thickness deviation can be controlled within ±30μm.

Interfacial behavior is an easily overlooked yet extremely important dimension in hot rolling. The contact interface between the rolls and the workpiece serves as a medium for force transmission, a channel for heat conduction, and a site for oxide scale formation. The interfacial friction state directly affects rolling force parameters and roll wear, while interfacial oxidation behavior determines the product surface quality. Statistics show that over 60% of product surface quality defects are related to improper control of high-temperature oxidation behavior. Therefore, effectively controlling interfacial behavior through optimization of lubrication conditions, roll surface condition, and descaling processes is a crucial way to improve the quality of hot-rolled products.

The Intrinsic Mechanisms of Organizational Evolution and Performance Regulation

The final properties of hot-rolled products depend on their microstructure characteristics, and the evolution of the microstructure is the result of the combined effects of temperature, deformation, and time.

Austenite recrystallization is the most important microstructure evolution mechanism during hot rolling. Recrystallization includes two types: dynamic recrystallization (occurring during deformation) and static recrystallization (occurring after deformation). Studies show that the dynamic recrystallization model of Q235B experimental steel can be expressed as a Z-parameter function, and the dynamic recrystallization grain size model is dd = 24.08454·Z^(-0.00727). By drawing recrystallization region diagrams, the recrystallization state of each stand during hot continuous rolling can be determined—for example, the F3 stand on a certain production line is in the partial recrystallization region of austenite, which is precisely the cause of the mixed-grain microstructure.

Phase transformation during post-rolling cooling is another crucial step in microstructure evolution. When the cooling rate is less than 0.5℃/s, austenite primarily transforms into ferrite + pearlite; when the cooling rate exceeds 0.5℃/s, bainite begins to appear in the microstructure; and when the cooling rate exceeds 20℃/s, martensite appears. Increased cooling rate lowers the phase transformation temperature, accelerates the phase transformation due to deformation, and reduces grain size. For ferrite-pearlite high-strength steels, this results in high microstructure and property stability, and excellent overall performance.

Precipitation strengthening is the primary strengthening mechanism of microalloyed steel. Adding microalloying elements such as Nb, V, and Ti to steel causes them to dissolve at high temperatures and precipitate as carbonitrides during cooling, thus pinning dislocations. Studies have shown that precipitates larger than 83 nm can lead to crack initiation. Reasonable precipitation strengthening should control the precipitate size within the 20-50 nm range; these fine precipitates can significantly improve strength without compromising ductility.

Traditional hot rolling process system and production line configuration

Full Process Analysis

The typical process flow of traditional hot continuous rolling includes: slab heating → high-pressure water descaling → rough rolling (multi-pass reversible rolling) → flying shear → finish rolling (multi-stand continuous rolling) → laminar flow cooling → coiling.

The heating process is the starting point of hot rolling. Slabs are typically heated in walking beam furnaces, with the exit temperature controlled between 1150-1250℃. The furnace employs a computer-controlled combustion system to achieve precise temperature regulation and energy optimization. Modern walking beam furnaces can control slab temperature uniformity within ±15℃, effectively reducing rolling force fluctuations caused by uneven temperature.

The descaling process is crucial for ensuring surface quality. After the slab exits the furnace, it must pass through a high-pressure water descaling device to remove the surface iron oxide scale. The descaling water pressure is typically 18-22 MPa, and multiple nozzles are arranged to achieve full coverage of the upper and lower surfaces of the slab. The effectiveness of descaling directly affects the surface quality of the finished product—incomplete descaling will cause iron oxide scale to be pressed in, forming surface defects.

The roughing rolling process is the main stage for thickness reduction. A roughing rolling mill typically consists of 2-4 stands and employs a reversible rolling method. The slab thickness is reduced from 200-250 mm to an intermediate slab of 30-60 mm. The reduction rate in the roughing rolling stage accounts for more than 80% of the total deformation and has a significant impact on subsequent microstructure evolution.

The finishing rolling process is the core step that determines product precision. A finishing rolling mill typically consists of 6-7 four-high stands connected in series, employing a continuous rolling method. The strip undergoes final thickness reduction in the finishing mill, while simultaneously achieving shape control and final rolling temperature control. The thickness deviation at the finishing mill exit can be controlled within ±30μm, with a 100% success rate in strip threading.

Cooling and coiling processes are crucial for microstructure control. After finishing rolling, the strip steel undergoes a controlled cooling path via a laminar flow cooling system before finally entering the coiler for coiling. The precision of coiling temperature control directly affects the final microstructure and properties of the product. Taking X80 pipeline steel as an example, the low-temperature coiling process places extremely high demands on the precision of coiling temperature control.

Core equipment technical characteristics

The roughing mill is the first deformation device in a hot strip mill. Modern roughing mills mostly adopt a four-high reversible structure, with work rolls approximately 1000-1200 mm in diameter and support rolls approximately 1500-1600 mm in diameter. A vertical roll mill is usually installed before the roughing mill to control the slab width. The vertical rolls employ short-stroke control technology, which can control the width deviation at the beginning and end to within 10 mm.

The finishing mill is the core equipment that determines the precision of the product. A modern finishing mill consists of 6-7 four-high mill stands, with work rolls approximately 700-850mm in diameter and roll lengths up to 2300mm. The finishing mill employs a hydraulic reduction system, which offers fast response and high control precision. The configuration of roll bending and roll shifting devices significantly enhances the ability to control the sheet shape.

Laminar flow cooling systems are crucial equipment for controlling microstructure evolution. Composed of upper and lower manifolds, laminar flow cooling achieves precise control of the cooling path by adjusting the water flow rate and the number of cooling stages. The heat transfer coefficient of laminar flow cooling is a key parameter in the temperature model, directly affecting the accuracy of coiling temperature control.

The coiler is the end-of-line equipment in a hot rolling line. Coils typically employ an underground coiling method, with a drum diameter of approximately 760mm. The application of technologies such as coiling tension control and auxiliary coiling roller control ensures the uniformity of the steel coil and the quality of both the inner and outer coils.

Automated control system architecture

Modern hot strip rolling automatic control systems adopt a hierarchical architecture, typically divided into L0 equipment control level, L1 basic automation level, L2 process control level, L3 production control level, L4 production management level, and L5 enterprise management level. Among these, levels L1 and L2 are most closely related to production and product quality.

The L1 basic automation system employs a high-end PLC system, enabling rapid control of position and pressure closed-loop systems such as AGC and APC within milliseconds. This basic automation system is responsible for real-time control functions such as mill reduction, speed control, looper control, and temperature control, forming the foundation for ensuring a stable rolling process.

L2 process control systems typically consist of multiple high-performance PC servers, primarily running rolling process automation application software. The process control system is responsible for model calculation, setpoint prediction, and self-learning correction, and is the core component for achieving high-precision control.

Mathematical models are the core of process control systems. With the development of computer control technology for hot strip rolling, mathematical models have evolved from traditional engineering models to modern models based on numerical analysis and artificial intelligence. The finite element method can discretize continuous deformable bodies and solve complex problems that are difficult to solve with classical theory; neural networks have characteristics such as self-learning, self-organization, self-adaptation, and nonlinear dynamic processing, making them particularly suitable for handling complex nonlinear processes.

Global Technology Landscape: Evolution Paths and Innovation Contributions of Major Countries

United States: Origins of Technology and Sources of Innovation

The United States is the birthplace of hot strip rolling technology. In 1924, Aslan Steel in the United States built the world’s first 1470mm wide strip hot strip rolling mill, pioneering modern hot rolling of plate and strip. From the 1950s to the 1960s, the United States continued to lead innovation in the field of hot strip rolling automation—in 1960, McLaurence Steel Company first used computers to set and control the roll gap and speed of its finishing mill, and in 1961, U.S. Steel’s Great Lakes plant first adopted speed-increasing rolling technology.

However, after the 1980s, the United States gradually lost its leading position in hot continuous rolling technology to Japan and Europe. The US steel industry faced the dilemma of overcapacity and high costs, and lagged behind in technological innovation and production line upgrades. But short-process companies, represented by Nucor, made breakthrough progress in the field of thin slab continuous casting and rolling, becoming global pioneers in short-process technology.

Japan: Ultimate Efficiency and Technological Innovation

The development of hot strip rolling technology in Japan began in the 1960s. In just a few decades, it has completed the leap from importing and assimilating technology to independent innovation, and has become one of the world’s leading countries.

The commissioning of the 2286mm hot strip mill at the Kimitsu plant in Japan in 1969 marked a new stage in the development of hot strip rolling technology towards larger scale and higher speed. In the 1970s, Japanese hot strip rolling technology continued to develop in the direction of larger scale and higher speed, with the annual output of the mill reaching 6 million tons, the maximum weight of a single coil reaching 45 tons, the thickness of the finished product decreasing to 0.8mm, and the rolling speed increasing to 28-30m/s.

Japanese companies have developed unique technological advantages in areas such as automated control of hot strip mills, roll materials, and strip shape control. JFE Steel Corporation’s Super Steel Control technology achieves micron-level thickness precision control and extremely stable mechanical properties with minimal fluctuations.

Europe: Technological Innovation and Green Leadership

Europe has played a significant role in the development of hot strip rolling technology and possesses a rich heritage in hot strip rolling process technology and equipment manufacturing.

European steel companies are at the forefront of energy conservation and carbon reduction technologies worldwide. Faced with stringent environmental regulations and high energy costs, European companies place great emphasis on developing energy-saving and emission-reduction technologies for hot rolling processes. ThyssenKrupp Steel in Germany has developed various waste heat recovery technologies, using waste heat from the hot rolling process for power generation or heating; SSAB in Sweden pioneered a “fossil-free steel” technology roadmap.

In recent years, Europe has made significant breakthroughs in short-process technology. Primetals’ ESP (Endless Strip Production) technology achieves complete continuity between continuous casting and rolling, representing the highest level of thin slab continuous casting and rolling technology. Globally, there are 14 completed or under-construction endless strip production lines with a total capacity exceeding 21 million tons.

Innovative Practices and Data Analysis of Hot Rolling Technology in China

Empirical Analysis of Process Optimization and Quality Improvement

Coiling temperature control is a key factor affecting the microstructure and properties of hot-rolled strip steel. Statistical data from Baogang’s CSP line producing Q235B strip steel shows that variations in finished product thickness and coiling temperature significantly impact yield strength—as coiling temperature decreases and finished product thickness decreases, yield strength tends to increase. A coiling temperature within the range of 650-680℃ yields better overall mechanical properties.

The ability to develop thick-gauge products is a crucial indicator of the level of hot strip rolling technology. Jiuquan Iron & Steel (JISCO), through process optimization and product structure adjustment projects, integrated CSP (Chemical Slab Rolling) with conventional hot strip rolling technology, achieving “mixed rolling” of thin and thick slabs. Product specifications expanded from 12.7 mm to 25.4 mm, and steel grades increased from 9 categories and 57 types to 17 categories and 172 types. This project saved 2 billion yuan in investment compared to building a new production line of the same scale, and increased the annual output of hot-rolled coils from 2.5 million tons to 4.5 million tons, an increase of 80%.

Cooling process optimization is crucial for the development of high-end products. For high-end products such as X80 pipeline steel that require low-temperature coiling, the accuracy of traditional mechanistic models for calculating water-cooling heat transfer coefficients is limited, making it difficult to meet control requirements. By constructing a temperature prediction model that integrates data and mechanisms, and using artificial neural networks to predict heat transfer coefficients, the coiling temperature prediction error can be reduced by 5℃, the mean square error by 76.8%, and the average relative error by 49.5%.

Exploration of digital and intelligent transformation

Digitalization and intelligentization are important directions for the development of hot strip rolling technology. The deep application of digital technologies such as the Industrial Internet of Things, big data analysis, digital twins, and artificial intelligence is driving hot strip rolling production lines towards intelligence and greening.

In the realm of process control optimization, data-driven models have replaced traditional mechanistic models, leading to a significant improvement in control precision. A temperature prediction model—which integrates both data-driven and mechanistic approaches—calculates internal heat transfer within steel strips by solving one-dimensional heat conduction differential equations, while simultaneously employing a data-driven model to predict heat transfer coefficients, thereby substantially enhancing the accuracy of surface heat transfer calculations.

Regarding closed-loop quality control, digital technologies have facilitated a transition from reliance on empirical judgment to precise prediction. By establishing predictive models for mechanical properties, strip shape, and other parameters, product quality can be forecast in real-time during the rolling process; this enables early warning of potential quality defects and allows for the dynamic adjustment of process parameters.

In the domain of intelligent equipment operation and maintenance, predictive maintenance technologies—driven by condition monitoring and data analytics—enable the early identification of equipment failure risks, thereby reducing unplanned downtime. Furthermore, regarding energy efficiency improvements, energy consumption optimization technologies powered by big data analytics can pinpoint specific process stages exhibiting abnormal energy usage, thereby guiding efforts to conserve energy and reduce consumption.

Practical application has demonstrated the remarkable effectiveness of these digital technologies. The production efficiency of technical personnel involved in the hot rolling process has increased by over 30%, while the comprehensive finished product yield rate has reached 97.02%.

Comparison and Integration of Traditional Hot Continuous Rolling and Short-Process Technology

Comparison of the advantages of the two technical approaches

Traditional hot rolling and thin slab continuous casting and rolling are the two major technical routes in the field of hot rolling of plate and strip, each with its own advantages.

The advantages of traditional hot continuous rolling are mainly reflected in the following aspects: First, it has strong adaptability to various products, and can produce a wide range of products from ordinary carbon structural steel to high-strength steel, pipeline steel, silicon steel, stainless steel and so on; Second, it has a wide range of specifications, especially in the production of thick products (>12.7mm) which is irreplaceable; Third, it has high technical maturity, rich operation and maintenance experience, and good product quality stability.

The advantages of continuous casting and rolling of thin slabs are mainly reflected in the following aspects: First, the process is compact, with the production line length shortened by 60%-80% compared to the traditional process, resulting in a significant reduction in floor space and civil engineering investment; Second, energy saving and consumption reduction, with energy consumption per ton of steel reduced by more than 30% compared to the traditional process; Third, outstanding production capacity for thin specifications, enabling stable production of ultra-thin specifications that are difficult to achieve with the traditional process; Fourth, the billet solidification speed is fast, and the grain refinement effect is good, which is conducive to improving product performance.

Mutual learning and technological integration

The two technological approaches are not mutually exclusive, but rather develop together through mutual learning. Traditional hot continuous rolling continuously absorbs advanced concepts from short-process technologies, making continuous improvements in areas such as furnace optimization, descaling processes, and finishing rolling molds. Thin slab continuous casting and rolling, on the other hand, has achieved breakthroughs in expanding its product range, extending to high-end products such as high-grade silicon steel, high-strength steel, and pipeline steel.

The latest achievement in technological integration is the completion and commissioning of a combined CSP and conventional hot strip rolling production line. The world’s first high-efficiency integrated CSP and conventional hot strip rolling production line was built at Jiuquan Iron & Steel Group in 2026. This line adds a thick slab roughing mill unit to the middle section of the existing CSP heating furnace A line, integrating cutting-edge technologies such as roughing mill cascading and transverse furnace insulation, achieving “mixed rolling” of thin and thick slabs. This innovative model breaks the constraints of traditional single-mode production lines, providing a replicable and referable solution for the transformation of similar production lines worldwide.

The continued evolution of traditional hot rolling

Faced with competition from short-process technologies, traditional hot strip rolling is continuously evolving in the following directions:

First, there is the trend towards high-end products. Traditional hot continuous rolling mills are leveraging their product range advantages to expand into high-end product areas such as high-grade silicon steel, ultra-high-strength steel, and high-performance pipeline steel. The development of high-grade non-oriented silicon steel and oriented silicon steel requires addressing issues such as corrugated defects caused by coarse columnar crystals in the cast billet and the surface quality of high-Si steel.

Secondly, the process has been streamlined and made more efficient. Production efficiency has been continuously improved through measures such as optimizing the roughing mill, upgrading the finishing mill model, and improving roll changing technology. The application of continuous heat treatment and cross-cutting processes has increased the rolling line speed to 12 m/s.

Third, intelligent control. New-generation information technologies, such as digital twins and machine learning, are driving the evolution of traditional hot strip rolling towards intelligent control. Temperature prediction models based on data and mechanism fusion, and mechanical property prediction models based on machine learning, have significantly improved control accuracy and quality stability.

Fourth, we are promoting green production. Through measures such as improving the efficiency of heating furnaces, recovering and utilizing waste heat, and recycling laminar flow cooling water, we are continuously reducing process energy consumption and fresh water consumption. The water recycling rate of advanced hot rolling mill production lines has reached over 98%.

Conclusions and Outlook

in conclusion

First, traditional hot rolling is a complex process involving the coupling of multiple fields: temperature, deformation, microstructure, and properties. The core of its process control lies in the coordinated regulation of the temperature field, deformation field, and interfacial behavior. A deep understanding of the principles of physical metallurgy is the theoretical foundation for achieving rational design of hot rolling processes.

Second, the development of global hot strip rolling technology has gone through the technological evolution from the first generation to the third generation. The United States is the origin of the technology, Japan has promoted the development of large-scale and high-speed rolling, while China has developed from the introduction and assimilation of foreign technologies to independent innovation.

Third, traditional hot rolling has irreplaceable advantages in terms of product range, production of thick specifications, and development of high value-added products. At the same time, it is absorbing the advanced concepts of short-process technology and is continuously evolving towards green and intelligent directions.

Fourth, digitalization and intelligentization are important directions for upgrading traditional hot rolling technology. The application of technologies such as digital twins and machine learning can significantly improve process control accuracy and quality stability. Temperature prediction models that integrate data and mechanisms can reduce coiling temperature prediction errors by more than 5°C.

Fifth, traditional hot strip rolling and short-process technology are learning from each other and developing in an integrated manner.

Technology Outlook

Looking ahead, traditional hot strip rolling technology will continue to develop in the following directions:

First, more precise process control. Data-driven and mechanism-based modeling methods, and machine learning-based predictive control technologies, will drive hot strip rolling process control towards higher precision. The accuracy of coiling temperature prediction, thickness control, and shape control capabilities will continue to improve.

Second, higher quality and more advanced products. The rapid development of strategic emerging industries such as new energy vehicles and high-end equipment manufacturing will continue to increase the demand for high-strength steel, ultra-high-strength steel, and high-grade silicon steel, driving traditional hot strip rolling towards high-end applications.

Third, greener and lower-carbon production. The research and application of technologies such as furnace waste heat recovery, laminar flow cooling water recycling, and hydrogen heating will promote energy conservation and carbon reduction in hot strip rolling processes.

Fourth, more intelligent control. The deep integration of digital technologies such as the Industrial Internet of Things, big data, digital twins, and artificial intelligence will drive the intelligent development of hot strip rolling process control, achieving adaptive optimization of process parameters and precise control of product quality.

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