Advances in Thermomechanical Treatment for Steel Plates

Thermomechanical treatment (TMT) and thermomechanical controlled processing (TMCP) have become essential in the production of high-performance steel plates.

By combining controlled rolling and accelerated cooling, TMT enables the creation of steel plates with a unique balance of strength, toughness, and weldability properties that are increasingly demanded in modern engineering and infrastructure projects.

What is Thermomechanical Treatment?

TMT is a composite process that merges plastic deformation (rolling) with controlled thermal cycles.

Unlike conventional heat treatment, which relies solely on heating and cooling, TMT leverages the synergy between deformation and phase transformations to refine grain structure and enhance mechanical properties.

Key Principles

• Deformation Strengthening: Rolling introduces dislocations and refines grains, boosting strength and toughness.
• Phase Transition Strengthening: Controlled cooling transforms austenite into fine ferrite, bainite, or martensite, further enhancing properties.
• Microalloying: Elements like niobium, vanadium, and titanium are added to promote precipitation strengthening and grain refinement. 

Process Stages

1. Reheating: Steel is heated to dissolve previous microstructures.
2. Controlled Deformation: Rolling at specific temperatures, both in recrystallization and non-recrystallization regions.
3. Controlled Cooling: Accelerated cooling to induce desired phase transformations.
4. Optional Tempering: Fine-tuning the balance between strength and ductility.

Recent Technological Innovations (2020–2025)

Advanced Cooling Technologies

• Continuous Online Control (CLC™) and CLC-μTM: Real-time, precise control of cooling rates ensures uniform microstructure and mechanical properties across large plates. 
• Super-OLAC: Achieves nucleate boiling immediately upon cooling, bypassing inefficient phases and reducing residual stresses. 
• Reduced-Distortion Cooling: Optimized water crown profiles and advanced nozzle arrangements minimize temperature gradients and plate distortion. 

Process Optimization and Modeling

• Computational Material Design: Predicts microstructural evolution and final properties, accelerating new steel grade development. 
• Integrated Process-Metallurgical Models: Link process conditions to microstructural changes for real-time quality assurance. 

Microalloying and Alloy Design

• Trace Additions of Niobium and Titanium: Refine grain size, delay recrystallization, and enhance precipitation strengthening, enabling higher strength at lower carbon equivalents. 
• High-Purity Steelmaking: Advanced dephosphorization and vacuum degassing reduce impurities, improving toughness and weldability. 

Surface and Post-Treatment Innovations

• Surface Hardening: Techniques like laser cladding and induction hardening boost wear resistance for mining and construction applications. 
• Heat-Assisted Incremental Bending: Enables efficient shaping of thick, double-curved plates with reduced residual stress. 

Technical Advantages and Performance Characteristics

Microstructural and Mechanical Benefits

Note

• Strength & Toughness: TMCP steels achieve yield strengths up to 1300 MPa and maintain high impact toughness at sub-zero temperatures.  
• Weldability: Lower carbon equivalent values enable easier welding and reduce the risk of hydrogen-induced cracking. 
• Formability: Excellent bendability and edge-working characteristics, even after significant cold forming. 
• Fatigue & Fracture Resistance: Lower fatigue crack growth rates and higher fracture toughness due to refined microstructure. 
• Economic Benefits: Elimination of costly post-rolling heat treatments and reduced alloying requirements lower overall costs by up to 10% in large projects