Advanced high strength steels for automotive industry

Advanced high strength steels for automotive industry

 

 

High-strength steel used in the automotive field can be divided into ordinary high-strength steel (High Speed Steels, HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (Ultra High Strength Steel, UHSS) according to different strengthening mechanisms. . Among them, advanced high-strength steel and ultra-high-strength steel have high strength and formability, and are important materials for lightweighting the car body and ensuring safety.

In recent decades, advanced high-strength steel for automobiles has been the focus of materials research and development. The World Steel Association divides it into three generations based on its research and development history and characteristics: the first generation of ferrite-based AHSS steel has a strong plastic product of 10 to 20 GPa·%; the second generation of austenite-based AHSS steel The strong plastic product of AHSS steel is 50-60 GPa·%. Its high alloy content and difficult production process control lead to high costs; the third generation AHSS steel improves the strength and plasticity of the first generation AHSS steel and reduces the alloy content of the second generation AHSS. Developed with two goals in mind and production cost, the third-generation multiphase AHSS steel has a strong plastic volume of 30 to 70 GPa·% through fine control of multiphase, metastable and multiscale structures.

At present, domestic steel mills already have the production capacity of advanced high-strength steels such as DP, CP, TRIP, TWIP, Q&P, and MS, which are used for internal and external covering parts, various structural parts, beams and other automotive parts. Its mechanical properties cover a very wide range, meeting the automotive requirements for strength, stiffness, collision energy absorption safety, comfort and processability, and providing more choices for automotive materials and material selection.

However, the proportion of high-strength steel in mainstream international models has exceeded 70%, of which the application proportion of independent brands is as high as 45%. As the country with the most common application of high-strength steel, China's car body usage ratio is close to 50%, and is expected to reach 60% to 65% in the future. However, the use proportion of ultra-high-strength steel and advanced high-strength steel is relatively lagging behind, currently only 5%, but it is expected to have room for three times improvement in the future.

Industry experts believe that advanced high-strength steel and ultra-high-strength steel have obvious advantages in terms of collision resistance, processing technology and cost, and can meet the dual technical needs of reducing vehicle mass and improving collision safety. From a cost and performance perspective, these two materials are currently the best choices to reduce body weight and improve crash safety.

A statistical analysis of the relevant material data of the models displayed at the "European Car Body Conference" and "China Lightweight Car Body Conference" in recent years shows that the application level of high-strength steel for passenger cars in my country has reached the world's advanced level. The average high-strength steel consumption of products displayed at the European Auto Body Conference is 56.7%, with a maximum of 73%; the average high-strength steel consumption of products displayed at the China Lightweight Car Body Conference is 62%, with a maximum of 70.4%.

From a global perspective, although the application of materials such as aluminum alloy and carbon fiber has achieved many successful cases, high-strength steel still occupies an important position that cannot be ignored in corporate material strategies. Each major OEM has its own considerations and decisions when selecting body materials and forming processes. The key factors that determine their high-strength steel material strategy are the product specifications, performance, price and supply chain support capabilities of steel companies.

Based on the above factor analysis, with the continuous development of my country's high-strength steel production technology, the varieties and strength levels of automotive steel have reached basically the same level as developed countries. my country's world-leading advantage in the development and production of third-generation steel with high strength and high plasticity characteristics has been recognized globally as one of my country's major advantages in the field of high-strength steel. This advantage will provide strong support for my country to further promote the application of high-strength steel.