1.4021 Stainless Steel: Equivalents, Properties and Heat Treatment

Engineers sourcing 1.4021 stainless steel quickly discover that the same material is called by several names: X20Cr13 in EN terminology, AISI 420 in the United States, SUS420J1 in Japan and 2Cr13 in China. Understanding how these designations map to each other - and how the composition and heat treatment vary between standards - is essential for material substitution, purchasing and quality control. This article covers the equivalents, the verified composition and mechanical property data, and the practical heat-treatment rules that determine final performance.

1. What Is 1.4021 Stainless Steel?

1.4021 is a martensitic stainless steel defined in EN 10088-1 under the steel name X20Cr13. The designation decodes as: X = high-alloy steel, 20 = nominally 0.20 % carbon, Cr = chromium, 13 = nominally 13 % chromium. Martensitic grades harden by austenitising and quenching, which makes them magnetic and gives them high hardness and wear resistance. The trade-off is lower corrosion resistance than austenitic grades such as 304 - 1.4021 is corrosion resistant in mildly corrosive, dry or lubricated environments, but not in strongly acidic or chloride-rich service.

2. International Equivalents of 1.4021

Standard	Equivalent Grade	Notes
EN (Europe)	X20Cr13 / 1.4021	Defined in EN 10088-1, -2 and -3
AISI / SAE (USA)	420 (Type 420)	Closest US designation; carbon range may differ slightly by specification
ASTM (USA)	A276 Type 420	Bar and mechanical components
JIS (Japan)	SUS420J1	JIS G4303 (bars) and G4304 (plate/sheet)
DIN (Germany)	X20Cr13	Identical chemistry; legacy designation now aligned with EN
GB (China)	2Cr13	GB/T 1220; used for pumps, valves, shafts

When substituting between these designations, always compare the full chemical specification: for example, AISI 420 in ASTM A276 allows C 0.15 % min with no upper limit, while EN 10088-1 fixes 1.4021 at C 0.16–0.25 %. For critical applications, require a certificate of the delivered heat rather than relying on the nominal designation.

3. Chemical Composition (EN 10088-1)

Element (wt%)	Min	Max
Carbon	0.16	0.25
Silicon	-	1.00
Manganese	-	1.50
Phosphorus	-	0.040
Sulfur	-	0.015 (0.030 max for free-cutting variants)
Chromium	12.00	14.00
Nickel	-
Molybdenum	-

Density is 7.70 g/cm³ per EN 10088-1. The material is delivered in the annealed (soft) condition or in the quenched-and-tempered condition, depending on the product form and application.

4. Mechanical Properties

Mechanical properties depend entirely on heat treatment. The values below follow EN 10088-3 for bar and EN 10088-2 for sheet/plate delivery conditions.

Condition	Property	Value
Annealed (+A)	Hardness	≤ 223 HB
Quenched and tempered (+QT)	Tensile strength	700–850 MPa
	Yield strength (0.2 % offset)	≥ 500 MPa
	Elongation	≥ 12 %
	Hardness after tempering	up to ≈ 50 HRC (low-temperature temper)

For wear-dominated applications the part is quenched and low-temperature tempered to reach hardness of roughly 45–52 HRC; for toughness-critical parts the tempering temperature is raised and hardness is reduced accordingly.

5. Heat Treatment and Processing

Hardening (austenitising): 980–1050 °C, followed by oil or air quenching. The full hardness depends on complete dissolution of chromium carbides at the austenitising temperature.

Tempering: 150–400 °C. Tempering between roughly 450 and 600 °C should be avoided because it produces a severe loss of toughness (475 °C embrittlement / temper-brittleness range for martensitic 13Cr grades).

Weldability: limited. The 0.16–0.25 % carbon makes the weld heat-affected zone hardenable; preheating (200–300 °C) and immediate post-weld tempering are recommended, and the weld should not be used in critical service without a full heat-treatment cycle.

Machinability: fair in the annealed condition (≤ 223 HB); machinability improves with appropriate tooling and cutting parameters, and a 0.015–0.030 % sulfur variant is available for improved free cutting.

6. Typical Applications

Pump shafts, impellers, valve seats and stems

Cutlery, kitchen knives and scissors

Turbine blades and steam-valve parts

Shafts, spindles and other wear-resistant mechanical components

Medical and surgical instruments (non-implant)

Fasteners and hardware in mildly corrosive environments

Frequently Asked Questions

What is the difference between 1.4021 and 1.4034?

1.4034 (X46Cr13) carries about 0.43–0.50 % carbon versus 0.16–0.25 % in 1.4021. The higher carbon gives 1.4034 higher maximum hardness and edge retention for cutting tools, at the cost of lower toughness. Choose 1.4021 for components that need impact resistance, and 1.4034 for knives and blades.

Is 1.4021 stainless steel suitable for knives?

Yes, for kitchen and utility knives where the blade is quenched and tempered to about 48–52 HRC. It holds an edge well but is less corrosion resistant than high-chromium martensitic grades; blades must be dried after use.

Can 1.4021 be welded?

Only with care: preheat to 200–300 °C, use matching or lower-carbon filler, and temper after welding to restore toughness in the heat-affected zone. For welded fabrication, 1.4021 is often replaced by low-carbon martensitic grades such as 1.4313 or by austenitic 304 where corrosion demands it.

What is the Chinese equivalent of 1.4021?

Grade 2Cr13 in GB/T 1220, with C 0.16–0.25 %, Cr 12.0–14.0 %. It is widely used for the same pump, valve and shaft applications.

How does 1.4021 compare with 304 in corrosion resistance?

304 (UNS S30400) is far more corrosion resistant because its austenitic structure with 18 % Cr and 8–10.5 % Ni resists most neutral and mildly acidic environments. 1.4021 is limited to dry, mildly corrosive or lubricated service; in wet or chloride environments it will rust.

Which standard governs 1.4021 delivery?

EN 10088-2 covers sheet/plate and strip, EN 10088-3 covers bars, rods, wire, sections and bright products, and EN 10088-1 defines the grade itself. Deliveries include a mill certificate to EN 10204 (typically type 3.1).