Improving Yield Strength Consistency of ASTM A182 F316L API Forging Valve Bodies
The in-depth examination and experimentation from forging ratio to quenching temperature
With the main capability of serving oil & gas customers the metal parts used in API applications, forging is one of Teamco’s major production capabilities to produce high strength valve metal parts. We can forge carbon steel and stainless steel valve metal parts to fulfill customer’s applications. Before proceeding machining to achieve the customer designs, we must first ensure that the forging quality meets the international standards, including both chemical compositions and physical properties. Heat treatment is usually the key procedure to achieve the required physical features, such as Tensile Strength, Yield Stregth and Hardness, etc. In some situations the Charpy V-Notch Impact Test will be required. We had an experience of forging the valve body in ASTM A182 F316L material which failed to consistently meet the ASTM minimum requirement of 25,000psi yield strength after solution heat treatment. The chemical composition was fully compliant. We realized that for such Austenitic stainless steel, function of the solution annealing was not basically for raising the strength. However, the mechanical testing repeatedly showed insufficient yield strength, resulting in product rejection and reduce production yield. A comprehensive metallurgical investigation was conducted to identify the root causes and optimize the entire forging and heat treatment process. Eventually the problem was overcome.
| Case: | Improving Yield Strength Consistency of ASTM A182 F316L API Forging Valve Bodies |
|---|---|
| Customer Country: | USA |
| Application: | Oil & Gas, API Application |
| Product Name: | Ball Valve Body 0.5” ~ 2” NPT F316L |
| Materials: | Hot Forging |
Customer Requirement
One of our customer required forged ball valve bodies made from ASTM A182 F316L material, with chemical composition fully compliant with the original specification. We faced an issue that after the solution annealing , the yield strength repeated failed to meet the minimum requirement of 25,000psi across the batch by testing the forged test coupons, even though the material chemistry itself was confirmed to be within specification.
Technical Issues or Challenges
F316L is a material with mechanical properties highly sensitive to solution treatment conditIon, thermal uniformity and post-forging cooling control. We initially presumed that the material may have been:
Over-softened by excessive solution heat treatment.
Unevenly heated due to small part size and improper loading arrangement.
Kept too long before quenching, allowing grain growth.
Kept too long before quenching, allowing grain growth.
Affected by insufficient quench water control, including water temperature stability and cooling transfer time.
Affected by insufficient quench water control, including water temperature stability and cooling transfer time.
Teamco Solutions
Step 1: Confirm the standard and test method<br>First, we confirmed that the 25,000psi minimum yield strength was the applicable ASTM A182 F316L requirement for this product requirement. We also verified that tensile samples were taken from the forged block and that the problem affected the entire batch, not just a single outlier piece.
Step 2: Review forging and heat treatment parameters
Next, we reviewed the forging and solution heat treatment process:
Next, we reviewed the forging and solution heat treatment process:
-The forging ratio was confirmed at 3:1 min. which effectively refines the grain structure.
-The solution treatment temperature was confirmed to be at least 1040°C.
-The transfer time from furnace to water quench tank needed to be very short.
-The quench water temperature had to be controlled stable.
-To control the grain size the holding time could not be excessive while maintaining complete carbide dissolution.
-Furnace loading and stacking were arranged properly to make sure the even heating across parts.
Step 3: Introduce vacuum furnace heat treatment for trial
We then conducted a trial comparison between the conventional furnace and vacuum furnace heat treatment. The key advantages of vacuum processing were:
-Clean, oxygen-free heating environment.
-Clean, oxygen-free heating environment.
-Reduced surface oxidation.
-Better thermal uniformity across small parts.
The trial showed that vacuum furnace heat treatment helped improve strength stability, but the increase in yield strength was limited rather than dramatic. This indicated that vacuum heating could improve consistency, but it was not a complete substitute for process optimization.
The trial showed that vacuum furnace heat treatment helped improve strength stability, but the increase in yield strength was limited rather than dramatic. This indicated that vacuum heating could improve consistency, but it was not a complete substitute for process optimization.
The trial showed that vacuum furnace heat treatment helped improve strength stability, but the increase in yield strength was limited rather than dramatic. This indicated that vacuum heating could improve consistency, but it was not a complete substitute for process optimization.
Step 4: Adjust the process when strength was still insufficient
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We further optimized the manufacturing route before we obtained fully satisfying result:
-Added controlled sizing deformation where allowed.
-Redesigned the forging ratio and post-forging cooling flow.
-Improved quench transfer time and water temperature control.
-Tightened furnace loading layout to ensure every part received uniform heat exposure.
-Control the final forging temperature to preserve fine grain structure while maintaining proper deformation.
-If necessary, we would need to select material suppliers capable of providing finer and more consistent grain structures.
-If necessary, we would need to select material suppliers capable of providing finer and more consistent grain structures.
Customer Benefits
- <p>Rather than modifying only one process parameter, a comprehensive manufacturing optimization program was implemented. By following this step-by-step validation and improvement plan, we eventually obtained the satisfactory yield strength. Our production yield and process reliability were substantially improved. The customer achieved:</p>
- Stable yield strength meeting the required ASTM A182 F316L target.
- Better batch consistency and lower test-result dispersion.
- Improved control of heat treatment quality for small forged valve bodies.
- Reduced risk of rejection in API and oil & gas applications.
- A more robust production process without changing the original material specification.
- <p>In summary, the successful result was achieved not by changing the material chemistry, but by correcting heat treatment uniformity, quench control, and forging-process stability. When combined with optimized forging and heat treatment parameters, the overall process stability and mechanical property consistency were significantly improved. The customer was impressed about our improvement program and determination to achieve the final requirements. Teamco treats every commitment as the top priority.</p>