Development of AISI 416 Stainless Steel by a Small Steel Mill (Part II)
Jul 03, 2024
Heat Treatment: The product undergoes softening annealing at 750-780°C and complete annealing at 840-870°C. It cools down to 590°C at a rate of 15°C/h in the furnace, followed by air cooling. The properties after annealing are typical values under ASTM A582 condition A.
For quenching and tempering, the quenching temperature of the product is 1010°C, followed by tempering at 660-680°C. Martensitic stainless steels (e.g., grades 410, 416, 420, and 431) can be hardened through the same quenching-tempering heat treatment process as carbon steel and low-alloy steel to achieve the quenched and tempered state specified in ASTM A582 condition T. To relieve stress, the recommended temperature is 210-250°C.
Note: Tempering of this steel in the 400-580°C range should be avoided as it may result in low impact resistance.
The ultimate tensile strength is 517 MPa, the yield strength is 276 MPa, the hardness is 262 HB, and the elongation is 30%.
Other Properties of 416 Stainless Steel: The density is 7.7 gm/cm³, the thermal conductivity is 30 W/m-K, and the PREN value is 14 (pitting resistance equivalent number). 416 stainless steel has excellent corrosion resistance to acids, alkalis, fresh water, and dry air. However, its corrosion resistance is not as good as that of non-ferrous metals, austenitic stainless steels, and 430 ferritic stainless steel containing 17% chromium. These steels can be hardened to achieve maximum corrosion resistance and smooth surfaces. High sulfur content 416 free-cutting steel is not suitable for use in environments containing chlorides and marine environments. Although 416 and other martensitic stainless steels are not as corrosion-resistant as austenitic or ferritic stainless steels, they still have good anti-corrosion performance, oxidation resistance, and high strength after quenching and annealing treatments. 416 stainless steel is commonly used in parts that require extensive machining and where corrosion resistance needs to reach the level of 13% chromium stainless steel. Typical applications include motors, pumps, nuts and bolts, valves, automatic screw machine parts, washing machine parts, pillar bolts, gears, etc.
AISI 416 steel has poor welding performance. Special attention should be paid during the welding process, before welding, and when preheating parts at 200-300°C. Post-weld heat treatment is necessary to avoid welding cracks caused by very hard and brittle areas in the heat-affected zone (HAZ). Post-weld heat treatment (PWHT) can include the following types: rehardening, annealing, or stress-relief annealing at 650-675°C. AISI 416 steel can be welded with 309 austenitic stainless steel filler to improve the ductility of the weld.
AISI 416 steel can be slightly cold-worked. If large deformation cold working is required, consider using 410 steel instead of 416 steel.
Improving the machinability of stainless steel is related to the number of particles that can enhance stress, which are active in the main shear zone and contribute to the formation of chips. Improving the machining performance of steel can reduce machining costs by up to 50% and increase production efficiency by 30%, thus potentially saving total costs. Adjusting the control process of MnS inclusions in 416 steel according to different processing conditions is mainly aimed at balancing the relationship between chemical composition and standard processes of steelmaking and processing. Changes in the composition of steel and the physical properties of sulfide inclusions (such as the transition from rod-like to spherical shape, reduction in inclusion size, and more uniform distribution) can improve the machining performance of 416 steel to the highest level of material quality standards.
In some countries, almost all pistol barrels are made of 416 stainless steel, which is produced according to specific requirements and is called 416R (R for rifle). Its sulfur content is maintained at 0.13%, lower than the lower limit of 0.15% stipulated in the 416 stainless steel standard. The longitudinal tensile stress of 416 steel barrels is essentially unaffected by the presence of elongated sulfide inclusions. The transverse tensile strength (perpendicular to the direction of elongated sulfide inclusions) is not the case. Due to the presence of elongated sulfide inclusions, the high-pressure resistance of the barrel is slightly reduced. This is an important factor because if the barrel is subjected to overload pressure, it will crack along the length direction of the sulfide inclusion (along the length of the barrel), which can cause the barrel to release pressure in advance, instead of bursting like a bomb and harming the user.
From "Stainless Steel" 2024 Issue 1
Americ Energy (CHINA) Co., Ltd. stands as a prominent manufacturer and distributor of a comprehensive range of stainless steel products, designed to cater to the diverse needs of various industries. Their offerings encompass stainless steel tubes, plates, strips, and square tubes, all manufactured to uphold the highest quality benchmarks.
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