HSLA Steel Rolling with Integrated Normalizing for Toughness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for rolling high-strength low-alloy steel face a trade-off between strength and toughness, and require an off-line normalizing step, which increases production costs and energy consumption, especially when producing round bar steel.
Innovation Solution
A rolling method that includes sequential steps of heating, descaling, rough rolling, continuous rolling, water cooling, finish rolling, and cold hearth cooling, using a converter continuous casting billet with specific chemical components and temperature control to eliminate the off-line normalizing step, resulting in a high-toughness high-strength low-alloy steel with a fine ferrite and pearlite structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an off-line normalizing step is added during rolling, then the strength and toughness of high-strength low-alloy steel are improved, but the production cost and energy consumption increase
Solution Approach 1:
The patent combines the normalizing process with the rolling process into a single integrated operation. The steel is heated to the austenite region and then directly rolled without separate normalizing treatment, achieving both grain refinement and dimensional control in one continuous process, thereby eliminating additional energy consumption and production costs
Solution Approach 2:
The patent performs heating to austenite transformation before rolling, preparing the steel in advance with the appropriate microstructure for subsequent deformation. This preliminary heating action enables the rolling process itself to achieve the grain refinement effect that would otherwise require separate normalizing treatment
2Ease of manufacture
If conventional rolling processes are used, then the production process is simpler, but the grain size is coarser and mechanical properties are inferior
Solution Approach 1:
The patent changes key process parameters including heating temperature (to austenite region), rolling temperature control, and cooling rate to achieve fine-grained microstructure. By optimizing these parameters, the process achieves superior grain size control (9.0 or above) and mechanical properties while maintaining production efficiency
Solution Approach 2:
The patent employs micro-alloying with specific elements (V: 0.05-0.10%, Ti: 0.02-0.05%, Nb: 0.02-0.05%) combined with the base steel composition to create a composite microstructure consisting of fine ferrite and pearlite, achieving enhanced mechanical properties through compositional complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves superior mechanical properties with tensile strength over 630 MPa, yield strength over 500 MPa, and a grain size of 9.0 or above, while reducing production costs and energy consumption by eliminating the off-line normalizing step.
Implementation Method 1
the temperature of the heating first zone is 900～1050℃, the temperature of the heating second zone is 1050～1150℃, and the temperature of the soaking zone is 1150～1210℃
Implementation Method 2
first water cooling, finish rolling, second water cooling, and cold hearth cooling
Data Source
AI summary
The method for rolling a high-toughness high-strength low-alloy steel, sequentially comprising the following steps: heating, descaling, rough rolling, continuous rolling, first water cooling, finish rolling, second water cooling, and cold hearth cooling; and using a converter continuous casting billet as a raw material, the continuous casting billet comprising the following chemical components in percentage by mass: C≤0.20, Si≤0.60, Mn: 1.00-1.70, Cr≤0.30, P≤0.020, S≤0.020, V: 0.05-0.10, Al≤0.03, and N≤0.025, with the balance being Fe and inevitable impurities. By using the rolling method, the actual grain size of the high-strength low-alloy steel can be refined; the comprehensive performance of the high-strength low-alloy steel is excellent; the metallographic structure is fine ferrite and pearlite; the grain size reaches 9.0 or above; the impact energy at −20° C. is greater than 100 J, and the impact energy at −40° C. is greater than 80 J.