Material Characteristics and Challenges

20CrMnMo is a high-strength carburizing alloy steel widely used in manufacturing critical components such as industrial gearboxes, crankshafts, and gears. Its exceptional mechanical properties, wear resistance, and toughness make it a preferred material for heavy machinery. However, during traditional free forging processes, localized overheating in natural gas furnaces or prolonged heating can lead to coarse overheated structures within the billet. Insufficient forging pressure or improper implementation of the "triple upsetting and drawing" process may result in retained defects, severely compromising fatigue life and operational safety.

Formation Mechanism of Overheated Structures

Research indicates that during heating in the austenite region, second-phase particles in 20CrMnMo steel inhibit grain boundary migration through "pinning effects." However, as temperature increases, these particles gradually dissolve, leading to rapid grain coarsening. Post-forging cooling rate variations result in three types of overheated structures:

1. **Rapid Cooling**: Insufficient time for second-phase precipitation

2. **Slow Cooling**: Agglomerated large second-phase particles

3. **Moderate Cooling**: Dispersed precipitation stabilizing the structure

Tiangong Forging's Innovative Solution

To address persistent stabilized overheated structures, Tiangong Forging has developed a **Triple Normalizing Process**:

1. **First Normalizing**: Transforms stabilized to metastable structures

Precise temperature control (900-920℃) achieves partial dissolution of grain boundary particles without excessive grain growth

2. **Subsequent Normalizing**: Stepwise refinement

Secondary treatment at 750-780℃ reduces second-phase density, achieving final grain size ≤ ASTM Grade 6

**Contact our material engineers today for tailored forging solutions**