Comparison of 410 and 420 Stainless Steel: Low-Carbon vs Medium-Carbon Martensitic Grade

410 and 420 are basic martensitic stainless steels, with the core difference being carbon content. 410 is low-carbon (C<=0.15%), focusing on toughness and weldability; 420 is medium-carbon (C=0.16-0.35%), focusing on hardness and wear resistance. Both are magnetic, suitable for different strength and wear resistance requirements.

	410 Stainless Steel	420 Stainless Steel
	C<=0.15, Si<=1.00, Mn<=1.00, P<=0.040, S<=0.030, Cr=11.50-13.50, Fe=Balance	C=0.16-0.35, Si<=1.00, Mn<=1.00, P<=0.040, S<=0.030, Cr=12.00-14.00, Fe=Balance
	Tensile Strength >=515MPa, Yield Strength >=310MPa, Elongation >=20%, Hardness <=45HRC	Tensile Strength >=725-820MPa, Yield Strength >=520-620MPa, Elongation >=12-15%, Hardness 48-57HRC
	-20℃ to 400℃ (continuous service)	-20℃ to 300℃ (continuous service)
	SUS410 (JIS), EN 1.4006, UNS S41000	SUS420J1/J2 (JIS), EN 1.4021/1.4028, UNS S42000/S42020

: 1. Hardness & wear resistance: 420's medium carbon content leads to higher hardness (48-57HRC) and excellent wear resistance; 410's low carbon content results in lower hardness (<=45HRC) and poor wear resistance. 2. Toughness: 410 has better toughness (impact toughness >=40J) and is not easy to brittle fracture; 420's toughness is poor (impact toughness >=15-25J), prone to chipping. 3. Weldability: 410 has better weldability, preheating not required for thin plates; 420 needs preheating to 200-300℃ before welding to avoid cold cracking. 4. Machinability: 410 is easier to machine in annealed state; 420's higher carbon content increases cutting resistance.

: 410 is suitable for components requiring medium strength, good toughness and weldability, such as low-pressure valve bodies, pump casings (clean water), hydraulic system components, food machinery brackets, and surgical instrument accessories. 420 is suitable for components requiring high hardness and wear resistance, such as kitchen knives, scissors, plastic mold cores, valve stems, mechanical seal rings, and textile machine parts.

Q1: What heat treatment process is suitable for 410 to balance strength and toughness? A1: Quench at 950-1000℃, oil cool + temper at 200-300℃, air cool; hardness can reach 35-40HRC, with good balance of strength and toughness; avoid tempering at 350-500℃ to prevent temper brittleness.

Q2: Why is 420 not suitable for components requiring high toughness? A2: Its medium carbon content leads to high hardness after heat treatment, but low toughness; in impact load environments, it is prone to chipping or cracking; for example, 420 kitchen knives are sharp but easy to chip if dropped.

Q3: Can 410 be used in food contact applications? A3: Yes. After passivation treatment with 20% nitric acid solution, it meets food safety standards; it is suitable for food machinery parts that do not contact strong acids for a long time, such as mixing tank brackets and conveying rollers.

Q4: What is the corrosion resistance difference between 410 and 420? A4: Similar, both have moderate corrosion resistance in dry environments; 420's slightly higher chromium content (12-14%) makes its corrosion resistance slightly better than 410 (11.5-13.5%); both are prone to rust in humid or chloride-containing environments.

Q5: How to select between 410 and 420? A5: Choose 410 if toughness, weldability and machinability are the main requirements; choose 420 if hardness and wear resistance are the core requirements and impact load is small.