What is age hardening ? This is a type of heat treatment process also known as precipitation hardening. It uses controlled heating and cooling to alter the microstructure of the material to strengthen and harden the metal alloy. It improves the performance of critical stainless steel pipes and stainless steel pipe fittings.
What is Age Hardening : Main Steps
Age hardening is divided into two main steps. First, the alloy is heated, which is called solid solution treatment, and it dissolves all the alloying elements. Then, the material is rapidly cooled, which is called quenching, and the alloying elements are “trapped” in solution. Next, the material is reheated to a lower temperature, which is called aging. The trapped elements form fine particles, which impede dislocation motion, which strengthens the material.
What is Age Hardening: Why it Matters
Age hardening significantly increases tensile strength and improves yield strength, making the metal more ductile.
Age hardening increases the hardness of the material and improves wear resistance. This is critical for components such as valve trim or pump shafts.
Age hardening increases fatigue life, allowing the material to withstand repeated stress cycles.
The process is tightly controlled and ensures that the passive layer remains intact to be able to maintain corrosion resistance.
Age Hardening VS Other Methods
| Method | Primary Mechanism | Typical Materials | Result |
|---|---|---|---|
| Age Hardening | Precipitation of particles | PH Stainless Steels,Nimonic Alloys | High Strength, good Ductility |
| Work Hardening | Plastic deformation, cold work | Austenitic SS, Copper | High Strength, less Ductility |
| Heat Treatment | Microstructure change | Carbon steels, some SS | Hardness, wear resistance |
Age-hardenable Nimonic Alloys
| Grade | Key Properties | Use in Piping |
|---|---|---|
| Nimonic 80A | High strength, creep resistance | Gas turbine parts, bolts |
| Nimonic 81 | Enhanced creep strength | Furnace components, bolts |
| Nimonic 90 | High creep/stress rupture strength | Hot work tooling, springs |
| Nimonic 115 | Extreme high-temp strength | High-performance turbine blades |
| Nimonic 901 | Good strength at moderate high temp | Jet engine rotors |
Products and Applications for Age Hardened Stainless Steel
- Forged Fittings: Elbows, tees and flanges can be age-hardened for use in high-pressure systems.
- Valve Fittings: Valve seats and stems are made of age-hardened stainless steel, which is resistant to wear and galling and ensures long-term sealing.
- Pump Shafts: These components require high strength and fatigue resistance, which is provided by age-hardening.
- High Pressure Pipes: Age-hardened pipes and tubes are used in critical pipelines to withstand extremely high pressures.
Sourcing Age Hardened Stainless Steel
A complete Material Test Report (MTR) is required. It verifies the precise composition of the alloy and ensures its performance.
Work with specialized suppliers of stainless steel pipe and fittings. They understand these alloy steels and can ensure proper fabrication and quality control,and are ISO 9001 and CE-PED certified.
This alloy is difficult to machine and requires special tools. Specific welding techniques are essential to ensure the integrity of the weld.
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