Introduction: Industrial Background and Market Demand
With the growing global demand for high-strength, high-wear-resistant components in the manufacturing sector, large shaft and roll forgings are playing an increasingly prominent role in fields such as metallurgy and heavy machinery. Driven by market demand and product structure optimization, the Forging Plant has successfully overcome the production challenges associated with large-scale rolling mill roll forgings through technological innovation and by leveraging the advantages of equipment such as 5-ton handling cranes.
This article takes 30Mn2 alloy steel as an example to provide a detailed analysis of the full-process implementation plan for large-scale rolling mill roll forgings, covering everything from material selection and process design to quality inspection.
I. Material Selection Criteria for Roll Forgings
Rolls face an extremely complex stress environment under actual operating conditions: the roll surface must withstand frequent impacts and friction, while the roll neck must endure multiple alternating stresses such as torsion and shear.
To balance strength, toughness, and surface hardness, we selected alloy forged steel (30Mn2) as the base material. Compared to castings, forged steel rollers offer the following significant advantages:
Excellent comprehensive mechanical properties: Combines wear resistance with resistance to thermal cracking.
Dense microstructure: Using alloy steel ingots as the parent material ensures uniform internal quality and effectively prevents macrosegregation.
Good machinability: Through scientific heat treatment, controlled cooling performance metrics can be precisely achieved.
II. Core Technical Requirements and Specification Parameters
This production process strictly adheres to the GB/T 3077—1999 standard. The core technical parameters are as follows:
Material Grade: 30Mn2
Mechanical Properties: Ensure that yield strength, elongation, and impact energy all exceed industry agreement standards.
Dimensions: Precisely controlled according to design drawings (see Figure 1 for an example), ensuring appropriate machining allowances for subsequent processing.
III. Forging Process Design: From Theory to Implementation
3.1 Charging and Forging Ratio Control
To ensure thorough fragmentation and intergranular bonding of the internal structure, the forging ratio is set at 3.5. Based on the finished product dimensions, the minimum weight of the raw material (steel ingot) is determined to be 3.7 tons.
3.2 Hot Forging Shrinkage and Allowance Allocation
Linear shrinkage after cooling must be accounted for during high-temperature measurements. We set the post-forging shrinkage rate for 30Mn2 steel at 1.2% and, based on this, allocate a machining allowance of at least 20 mm to ensure the finished dimensions are absolutely accurate.
3.3 Standardized Process Flow
We adopt a “three-heat” production scheme:
Bling Stage: Grind 3.7-ton steel ingot → Heat → Forge into Φ320mm billet (trim sprue and small end) → Surface grinding.
Forming Stage: Return billet to furnace for holding → Drawing → Reversing and drawing → Indenting.
Finishing Stage: Finishing to Φ165mm +5mm → Box cooling → Normalizing → Cutting off ends on a sawing machine → Final inspection.
IV. Key Details of Production Operations
Temperature Control Uniformity: Our process strictly prevents the formation of “hot and cold spots” during heating to ensure the temperature difference between the interior and exterior of the billet is maintained within a reasonable range.
Three-Cut Method: During initial blanking and measurement, ensure that the length of each individual piece does not exceed 2.23 m to improve material utilization.
Concentricity Control: Monitor tolerances in real-time during forging to prevent bending deformation and ensure the concentricity requirements for subsequent finishing operations.
Hardness Control: The Brinell hardness after heat treatment must be maintained between 207 and 269 HB.
V. Quality Inspection and Results Analysis
Sampling and testing of the mass-produced 30Mn2 rollers yielded extremely favorable results:
Dimensional Accuracy: The process capability index (Cp) reached 2.0, indicating that process control is in an “optimal state.”
Surface Quality: We uniformly control the depth of surface defects within 5 mm, meeting high-standard delivery requirements.
Mechanical Properties: All measured indicators exceed the specifications outlined in the technical agreement.
VI. Conclusion
Practice has proven that this three-heat treatment process—comprising “billet preparation, rough forging, and finish forging”—combined with scientific normalizing treatment, fully meets the production requirements for large 30Mn2 roll forgings.
CYKC Group is committed to providing high-quality industrial forging solutions to customers worldwide. If you have any questions regarding roll forgings, metallurgical spare parts, or technical processes, please feel free to contact our team of experts.