Stal nierdzewna 420 kontra stal nierdzewna 316

Today, we will discuss 420 stal nierdzewna vs 316. Both types of steel are called stainless steel, but they have fundamental differences and are used in very different applications. We will explain the differences between the two from various perspectives.

Stal nierdzewna 420 kontra 316: Classification and Microstructure

420 stainless steel is a martensitic stainless steel. Martensitic steels are characterized by a body-centered tetragonal crystal structure (bct). They are ferromagnetic at room temperature. Unlike ferritic stainless steels, martensitic stainless steels can be hardened by heat treatment, similar to non-stainless carbon steels and low-alloy steels.

316 stainless steel is an austenitic stainless steel. Austenitic stainless steels maintain a fully austenitic structure at room temperature due to the addition of nickel, an element that promotes the formation of austenit. They are typically non-magnetic in the annealed condition. Unlike martensitic steels, austenitic stainless steels cannot be hardened by heat treatment but can be cold worked. The reason for its corrosion resistance is the oxide film formed on the metal surface.

420 stainless steel vs 316: Kompozycja comparison

Element	420 Stainless Steel (%)	316 Stainless Steel (%)
Węgiel (C)	0.15 – 0.40	≤ 0.08
Chrom (Cr)	12.0 – 14.0	16.0 – 18.0
Mangan (Mn)	≤ 1.0	≤ 2.0
Krzem (Si)	≤ 1.0	≤ 0.75
Fosfor (P)	≤ 0.040	≤ 0.045
Siarka (S)	≤ 0.030	≤ 0.030
Nikiel (Ni)	≤ 0.50	10.0 – 14.0
Molibden (Mo)	≤ 0.50	2.0 – 3.0

420 stainless steel vs 316: Właściwości mechaniczne

1. Hardness. 420 stainless steel is specifically designed for high hardness and wear resistance. It can achieve hardness levels of 46-52 HRC (Rockwell C). The hardness of 316 stainless steel in the annealed state is lower than that of quenched 420 stainless steel, with a maximum value of approximately 90 HRB.
2. Wytrzymałość. 420 stainless steel has a martensitic structure, which gives it high strength and high yield strength. In the hardened condition, the 0.2% yield stress for martensitic stainless steels can exceed 1000 MPa, potentially reaching 1900 MPa. 316 stainless steel is an austenitic stainless steel with a tensile strength of 550 to 620 MPa (80 to 90 ksi) in the annealed condition. It has a significant difference between yield strength and tensile strength, and a high work hardening rate.
3. Toughness and Ductility. 420 steel has low impact strength at room temperature. It is prone to temper brittleness in the temperature range of 400-600°C (752-1110°F). Tempering at 1100°F (593°C) or higher temperatures can improve toughness, but at the expense of hardness. 316 stainless steel has excellent toughness and ductility. It retains its ductility even at low temperatures, a characteristic that is often applied in low-temperature working conditions.
4. Odporność na zużycie. 316 stainless steel is not as wear-resistant as 420 stainless steel, but it has anti-galling properties.

Odporność na korozję

420 stainless steel has moderate corrosion resistance, which is lower than that of austenitic stainless steel 316. 420 stainless steel is suitable for environments with low corrosion, such as air, fresh water, certain chemicals, and food acids. It is not recommended for use in high-stress components at low temperatures, as brittleness may occur. Stainless steel 361 exhibits good corrosion resistance in highly diluted or highly concentrated sulfuric acid¹.

Spawalność

420 is martensitic stainless steel, which has a higher carbon content than other types of stainless steel, resulting in poor weldability. 316 stainless steel exhibits good weldability and strong resistance to intergranular corrosion in the welded state; however, its corrosion resistance decreases after welding. The corrosion resistance of 316 stainless steel welds is comparable to that of forged 304 stainless steel.

Aplikacje

• 420 Stainless Steel: Its high strength, hardness, and wear resistance make it suitable for applications such as cutlery, dental and surgical instruments, nozzles, valve parts, gears, shafts, rollers, springs, knife blades, hand tools, and plastic molds. It is frequently used for plastic molds due to its combination of high strength, hardness, and corrosion resistance.
• 316 Stainless Steel: Because of its excellent corrosion resistance, particularly in chloride environments, and its good toughness and ductility, it is widely used. Applications include medical and dental devices (mechanical joints, brackets), mobile phone components (rocker key, battery lock), consumer products (watch cases, camera components, saw blade fasteners, electric toothbrush gears), and spectacles. It is also used in the food industry, architectural applications (exterior and interior cladding), chemical process equipment, and paper mill equipment. It is considered for seawater applications at elevated temperatures or high salinity.

Streszczenie

420 stainless steel performs well in applications requiring high hardness, strength, and wear resistance, but sacrifices corrosion resistance and weldability. 316 stainless steel offers resistance to pitting and crevice corrosion in chloride environments, along with good ductility and weldability, but its hardness and strength are lower than those of 420.

1. Davis, JR (red.). (1998). Metals Handbook Desk Edition (2nd ed., p. 916). ASM International. ↩︎