Customer Requirement

One of our customers required forged ball valve bodies manufactured from ASTM A182 F316L material, with a chemical composition fully compliant with the applicable specification.

During production, we encountered an issue after solution annealing: the yield strength of the forged test coupons repeatedly failed to meet the minimum requirement of 25,000 psi across the entire batch, even though the material chemistry was confirmed to be within specification.

Technical Issues and Challenges

F316L is a material whose mechanical properties are highly sensitive to solution heat treatment conditions, thermal uniformity, and post-forging cooling control. We initially considered that the material might have been affected by the following factors:

• Over-softening caused by excessive solution heat treatment
• Uneven heating due to the small part size or an improper furnace-loading arrangement
• Excessive delay before quenching, which may have allowed grain growth
• Insufficient quench-water control, including unstable water temperature or excessive transfer time

Teamco's Solutions

Step 1: Confirm the Standard and Test Method

First, we confirmed that the minimum yield strength requirement of 25,000 psi was applicable to the ASTM A182 F316L material specified for this product.

We also verified that the tensile test specimens were taken from the forged test blocks and confirmed that the issue affected the entire batch rather than being limited to a single outlier.

Step 2: Review the Forging and Heat Treatment Parameters

Next, we reviewed the forging and solution heat treatment processes. The key parameters included:

• The minimum forging ratio was confirmed at 3:1 to support effective grain refinement.
• The solution heat treatment temperature was confirmed to be at least 1,040°C.
• The transfer time from the furnace to the water-quench tank had to be minimized.
• The quench-water temperature had to remain stable and properly controlled.
• The holding time had to be controlled to prevent excessive grain growth while ensuring complete carbide dissolution.
• The furnace-loading and stacking arrangement had to provide uniform heating across all parts.

Step 3: Conduct a Vacuum Furnace Heat Treatment Trial

We then conducted a comparison trial using conventional furnace heat treatment and vacuum furnace heat treatment. The primary advantages of vacuum processing included:

• A clean, oxygen-free heating environment
• Reduced surface oxidation
• Improved thermal uniformity across smaller components

The trial showed that vacuum furnace heat treatment improved the stability and consistency of the mechanical properties. However, the increase in yield strength was limited rather than significant.

This result indicated that vacuum heat treatment could improve process consistency, but it could not replace the need for comprehensive forging and heat treatment process optimization.

Step 4: Further Optimize the Manufacturing Process

Because the yield strength remained insufficient after the initial adjustments, we further optimized the manufacturing process until satisfactory results were achieved. The improvements included:

• Introducing controlled sizing deformation where permitted
• Redesigning the forging ratio and post-forging cooling process
• Reducing the transfer time from the furnace to the quench tank
• Improving quench-water temperature control
• Optimizing the furnace-loading arrangement to ensure uniform heat exposure for every component
• Controlling the final forging temperature to preserve a fine-grain structure while maintaining sufficient deformation
• Evaluating material suppliers capable of providing finer and more consistent grain structures when necessary

Results and Customer Benefits

Rather than modifying only one process parameter, Teamco implemented a comprehensive manufacturing optimization program. By following a step-by-step validation and improvement plan, we ultimately achieved the required yield strength while significantly improving production yield and process reliability.

The customer achieved the following results:

• Stable yield strength meeting the ASTM A182 F316L requirement
• Improved batch consistency and reduced variation in test results
• Better control of heat treatment quality for small forged valve bodies
• Reduced risk of rejection in API and oil and gas applications
• A more robust production process without changing the original material specification

In summary, the successful result was achieved not by changing the material chemistry, but by improving heat treatment uniformity, quench control, and forging-process stability. When combined with optimized forging and heat treatment parameters, these improvements significantly enhanced overall process reliability and mechanical property consistency.

The customer recognized Teamco's structured improvement program and determination to meet the final requirements. At Teamco, every customer commitment is treated as a top priority.