Liu Zhenyu: "Iron Man" in the laboratory

With the development of New China for more than 70 years, the mainland steel industry has become the most globally competitive industry, with steel production of nearly 1 billion tons / year for many years. As the most used metal material, steel has always been a pillar raw material for marine, transportation, energy and other industries. Although China is already a steel power, but it is not a steel power, how can we achieve the transformation from a steel power to a steel power? Liu Zhenyu, deputy director of the State Key Laboratory of Rolling Technology and Continuous Rolling Automation of Northeastern University, gave the answer, he said: "Innovate steel technology, develop new steel products, promote intelligent manufacturing, improve the quality of varieties, and lay a solid foundation for China to become a steel power, in order to support the backbone of Chinese steel." ”

Nowadays, Liu Zhenyu and his team have completed the research and development of the project of "development and application of oxidation behavior control technology in the hot rolling process of steel" after difficult research, fully realized the localization of steel hot rolling technology, and won the second prize of the 2020 National Science and Technology Progress Award.

Liu Zhenyu team

Immerse yourself in research

In 2003, Liu Zhenyu returned to Japan from Hokkaido University and returned to his alma mater, Tohoku University, to engage in research on the high temperature properties of steel materials. In 2005, in accordance with the latest environmental protection requirements, the state dismantled the original girder production line and imported a full set of new production lines from Japan, and it was found that the Japanese girder plate production line had no pickling process. In order to solve this problem, major domestic steel companies have begun to develop pickling technology. Liu Zhenyu seized the opportunity of cooperation with Angang Steel Group Co., Ltd., and spent more than a year to take the lead in developing the "pickling-free hot-rolled steel plate production technology", so that large mainland automobile enterprises got rid of the dependence on imported automobile girder plates, "its indicators can reach the level of Japan's acid-free steel".

The development of "pickling-free hot-rolled steel production technology" is the first step in the development and application of oxidation behavior control technology for the hot rolling process of steel by Liu Zhenyu and his team, and they have explored some experience. At the same time, Liu Zhenyu also developed a production technology for easy pickling hot rolled steel. The thickness of steel oxide scale was reduced from about 12 μm to 5 μm to 8 μm, the Fe2O3 content was reduced from the original 20% to less than 2%, the pickling efficiency was increased by more than 20%, the amount of acid used in tons of steel was reduced by more than 15%, and the surface quality was significantly improved after pickling. The surface defect rate of high-strength pickling board was reduced from 2.7% before the implementation of the project to less than 0.6%, which met the strict requirements of automotive companies such as BMW and home appliance companies such as Haier, and completely replaced similar foreign products. In 2008, Liu Zhenyu and his team won the first prize of China Metallurgical Science and Technology Award. In 2009, the technology of easy acid washing and hot rolling steel was rated as a landmark technology for energy conservation and emission reduction in the metallurgical industry by China Metallurgical News.

Find a breakthrough in difficulties

After 2008, with the rapid development of the high strengthening trend of steel in the mainland, gradually developing from 510MPa to 610MPa, steel forming technology has also developed from stamping to roll forming, "at this time, according to Japanese standards to control iron oxide sheet, it is not very applicable."

To this end, Liu Zhenyu led the team to do a lot of basic research work, especially to study the influence of the chemical composition of high-strength steel on oxidation behavior in the rolling process, and found that this is a multi-factor coupling problem of "deformation + atmosphere + temperature". On this basis, Liu Zhenyu started from the actual hot rolling production conditions to establish a model of the thickness of the oxide scale and the structural evolution of the hot rolling process. Finally, the team developed a precise control technology for FeO phase change kinetics suitable for hot rolling environments, which can produce 400~800MPa class pickling steel, and the amount of cold working oxide peel powder is reduced from 100mg/dm2 to 3mg/dm2.

How hard is this technology? In 2015, the United States Axle Manufacturing International Holdings Co., Ltd. bid for 800MPa grade of high-strength steel for the production of axles from all over the world, and required that after the axle is formed, the amount of powder removed per square decimeter of oxide cannot exceed 10mg. "This is a very demanding requirement, Japan's Nippon Steel Company did not dare to pick up, nor did European steel companies dare to take it." Finally, Ma'anshan Iron and Steel Co., Ltd. (hereinafter referred to as "Ma Steel") took over the contract, and they worked with Liu Zhenyu's team to successfully produce ultra-high strength grade pickling steel in 2016, with a powder loss of less than 3mg per square decimeter of oxide peel. "The requirements are much lower than those of the American axle company, so Masteel basically monopolizes the supply of this raw material for the highest strength level of the axle, and the stable supply volume is about 15,000 tons a year."

Solving the production technology problem of ultra-high-strength grade pickling-free steel is the second step in the development and application of oxidation behavior control technology for the hot rolling process of steel by Liu Zhenyu and his team, but Liu Zhenyu is not satisfied with this. He is well aware that the surface quality of steel in the mainland has always been a big gap with European and American countries, and steel often has serious surface defects such as powder, spotting, color difference, etc., which seriously damages the dynamic bearing capacity and service life of steel, and restricts the pace of mainland steel to high-end manufacturing.

"The medium and thick plates produced in the mainland have a characteristic, and there is basically no big problem in terms of performance, but the surface quality of the products is relatively poor, and it is difficult to enter the international high-end market." Liu Zhenyu found through research that more than 70% of the surface quality problems are caused by improper oxidation control in hot rolling production. Therefore, if the oxidation behavior of the hot rolling process can be controlled, the surface quality problem of the steel can be solved to the greatest extent.

"At first, no one paid much attention to this matter, and it was felt that the surface quality could be solved by grinding." Liu Zhenyu told reporters that the international standard is to prohibit local grinding and one-time molding. Because if there is a local defect, the service life of the steel plate should be reduced by more than 30%, in other words, it is forbidden to produce any defects on the surface.

"We have done a lot of work, but the theoretical basis is the same, and it is all a multi-factor coupled oxidation behavior study of the hot rolling process." On this basis, Liu Zhenyu has developed a production technology for medium and thick plates with high surface quality. Taking Tangshan Iron and Steel Group Corporation (hereinafter referred to as "Tangshan Steel") as an example, before the technical research, the medium and thick plates produced by Tangshan Steel are supplied to Japanese high-end construction machinery manufacturing enterprises, and they will be returned 100%. Liu Zhenyu and the team after technical research, so that the production technology of high surface mass medium and thick plate in Tang steel to achieve industrialization, "such as Komatsu Machinery, Kobe Steel, their annual construction machinery steel basically 90% of the order from Tang Steel, basically formed a complete exclusive product." Liu Zhenyu proudly said that all the medium and thick plates produced by the enterprise can meet the needs of major national projects.

Shake hands with big data

In the "Guidelines for the Development of Key Common Technologies in the Industry (2017)", the Ministry of Industry and Information Technology clearly emphasized the need to strengthen the time-space tracking synchronization of big data in the steel process and the in-depth mining and analysis of big data, so as to achieve the goals of intelligent design of steel materials, customized manufacturing of products, prediction of steel microstructure performance, merger of steel grades and coordinated optimization of process parameters of the whole process of steel.

Liu Zhenyu and the team responded positively, they cooperated with Baosteel Meishan Company, Angang Steel and other enterprises to carry out in-depth research on big data preprocessing technology based on hot-rolled sheet and strip industry, starting from the actual hot-rolled production conditions, to establish a model of the thickness and structural evolution of the oxide scale in the hot rolling process; based on big data drive, the machine learning and intelligent optimization theory were applied to the dynamic optimization of model parameters, to achieve high-precision model development, and to build a hot-rolled oxidation intelligent control system. It has developed an intelligent steel manufacturing technology with organizational performance prediction and optimization as the core, which effectively solves the contradiction between the current large-scale production of steel enterprises and the personalized needs of users.

However, when the intelligent manufacturing technology of steel was first promoted, many technical personnel of steel companies did not trust it, so Hesteel Group Co., Ltd. organized a rolling experiment for Liu Zhenyu's team. The experiment cost 25 tons of steel and was worth 400,000 yuan. The results showed that the detected scale thickness and the results predicted by the ARTIFICIAL system were exactly the same. So far, the intelligent manufacturing technology of steel has been very smoothly applied in major steel enterprises, and the standardized control of the thickness of the oxide scale of a series of steel grades has been reduced by more than 15%, and the on-site one-time debugging has been successfully carried out and supplied in batches. "With this technology, we can reverse optimize the corresponding rolling process according to the needs of users in the process of controlling oxidation behavior." The intelligent steel manufacturing technology developed by Liu Zhenyu is not only widely used in China, but also exported to other countries, reaching the international leading level. This is also the third step in the development and application of oxidation behavior control technology for the hot rolling process of steel by Liu Zhenyu and his team.

Up to now, the complete set of control technology developed by Liu Zhenyu and his team with completely independent intellectual property rights has been applied to 19 steel enterprises such as Angang Steel, Hegang, TISCO, Baowu, Masteel, Liansteel, etc., including 45 production lines such as hot continuous rolling, medium and thin slab continuous casting and rolling, thin slab continuous casting and rolling, and medium and thick plate high-speed wire rod. The intelligent control system of steel oxidation behavior was successfully applied to the hot continuous rolling production line of Hyundai Iron & Steel 2# in South Korea, realizing the dynamic tracking and optimal control of oxidation behavior. As a common technology in the field of hot rolling, this technology can be promoted to different hot rolling production lines, covering a production capacity of more than 500 million tons per year, with good promotion and application prospects.

In the past 15 years, Liu Zhenyu has focused on doing one thing, researching the quality control technology of steel materials, leading the team to continuously innovate, solving many bottleneck problems faced by the steel industry, and has won 2 second prizes of the National Science and Technology Progress Award, 9 first prizes and 6 second prizes at the provincial and ministerial levels, more than 40 invention patents, and more than 300 papers.

In the future, Liu Zhenyu will continue to fight with the team in the wave of key technology development in the steel industry, exert his greatest strength, and hand over a satisfactory report card for the transformation of the mainland into a steel power.