1.2316 Steel Forging Process: Forging Ratio, Upsetting and Drawing Explained

Many mold shops buy 1.2316 steel by checking only chemical composition and delivery hardness. However, the forging route has a direct influence on center density, grain structure, segregation, ultrasonic test results, heat-treatment uniformity, and final mold life. Two blocks with the same grade and certificate can behave very differently if one received sufficient forging deformation and the other did not.

This article explains the practical 1.2316 steel forging process, including the difference between hot rolling and forging, the importance of forging ratio, repeated upsetting and drawing, temperature control, post-forging annealing, and the records a buyer should request.

Hot Rolling vs Forging: The 80 mm Process Boundary

In the production route described by the source document, approximately 80 mm is used as a practical boundary. Round bars and plates at or below this size can be produced by hot rolling, while thicker sections should be forged. The reason is deformation penetration.

Hot rolling is efficient for small sections. Heated billets pass continuously through rolls, providing high productivity and consistent dimensions. However, the total deformation at the center is limited as section thickness increases. Forging uses a hammer or hydraulic press to apply much greater reduction, allowing deformation to reach the core, break down the cast dendritic structure, and close internal looseness.

For large mold blocks, insufficient center deformation may leave segregation or shrinkage defects that are not visible on the surface. A large hot-rolled section may look acceptable externally while carrying a higher risk of internal discontinuities and uneven heat-treatment response.

Why Forging Ratio Matters for 1.2316 Steel

Forging ratio compares the original ingot cross-sectional area with the final forged cross-sectional area. A ratio of at least 4:1 is used as a practical minimum in the source manufacturing route. This means the starting ingot area is at least four times the final section area, providing enough deformation to improve the internal structure.

For example, a finished 1.2316 plate measuring 300 x 800 mm in cross section should originate from an ingot with enough cross-sectional area to achieve the specified reduction. If the ratio is too low, grain refinement and center consolidation may be incomplete. The consequences can include coarse grain, carbide segregation, hardness variation after heat treatment, local collapse, premature cracking, and inconsistent polishing.

When sourcing large 1.2316 blocks, ask the supplier for the forging process record. A professional record should identify ingot size, finished size, the calculated forging ratio, heating practice, and the major deformation steps.

Upsetting and Drawing: How the Core Is Worked

Upsetting compresses the ingot in the axial direction and increases its cross section. This forces metal to flow outward and subjects the center to compressive strain. Drawing then elongates the upset billet toward the required shape. One upsetting and drawing sequence forms one working cycle.

Repeated cycles are used for thicker sections because deformation is more difficult to transmit to the center:

• Up to about 100 mm: one upsetting and drawing cycle may be sufficient.
• About 100-200 mm: two cycles are commonly applied.
• About 200-400 mm: three cycles provide stronger center consolidation.
• Above about 400 mm: five cycles or a project-specific heavy-forging route may be required.

These values are process guidance rather than a substitute for engineering calculation. Ingot geometry, press capacity, alloy condition, temperature, and final shape all affect the actual schedule. For large plates, cross-direction working also improves isotropy compared with simple one-direction forging.

Forging Temperature for 1.2316 Steel

1.2316 is a martensitic stainless mold steel with a narrower forging window than many low-alloy steels. A typical starting range is about 1100-1150 deg C, while final forging should generally remain above about 850 deg C. Continuing deformation below the lower limit can increase cracking risk because transformation and loss of hot ductility have begun.

Temperature control becomes more difficult as the section grows. The surface loses heat quickly while the center remains hotter, creating a large temperature gradient. Operators must control reheating, deformation rate, bite size, and transfer time. Surface temperature alone is not enough to prove that the core is in the correct forging window.

Post-Forging Annealing Is Essential

Forging is not the end of the process. The steel should be annealed to reduce residual stress, soften the structure, and prepare it for pre-hardening or customer machining. Without proper annealing, the block can distort or crack during machining and later heat treatment.

The source route uses heating around 860 deg C followed by controlled furnace cooling. The exact schedule must be adjusted to section size and furnace conditions. A successful annealing cycle can reduce the forged hardness to approximately 20-25 HRC and significantly improve machinability.

How Buyers Can Verify the Forging Route

• Request the starting ingot size and finished section size.
• Confirm the calculated forging ratio and deformation route.
• Ask how many upsetting and drawing cycles were used for the section.
• Review heat-treatment and hardness records.
• Require ultrasonic testing for large or critical mold blocks.

Ultrasonic testing does not replace correct forging, but it helps confirm that no unacceptable internal discontinuities remain. The testing standard and acceptance level should be stated in the purchase order.

Frequently Asked Questions

Can hot-rolled 1.2316 steel below 80 mm be used?

Yes. For smaller sections, hot rolling can provide suitable quality and good cost efficiency. Forging is not automatically better when the section does not require it.

Is three-cycle upsetting and drawing better than two cycles?

For sections above about 200 mm, the extra working can improve center density, flow-line distribution, and uniformity. The benefit should be confirmed through the actual forging record and ultrasonic test results.

How is the forging ratio checked?

Calculate the ratio from the starting ingot cross section and the final forged cross section. Do not rely only on a verbal claim; ask for traceable process records.

Keyspark Steel can review the forging ratio, section size, delivery condition, and ultrasonic testing level required for your DIN 1.2316 plate, block, or round bar project.