Stainless Steel Grade 420J2 - High Hardness Tool Grade

Grade Overview and Equivalents

420J2 is a martensitic stainless steel with a nominal chromium content of 13%, designed for applications that need high hardness combined with moderate corrosion resistance. It is standardized in Japan under JIS G4303 as SUS420J2. Close equivalents are produced in other national systems, and each is specified with its own standard.

Designation cross-reference

Standard	Designation	Steel name
JIS G4303	SUS420J2	-
EN 10088	1.4034	X46Cr13
ASTM	Type 420 high-carbon variant	-
GB/T 1220	4Cr13	-
GOST	40X13	-

Note that the EN and GB grades carry slightly higher carbon than JIS SUS420J2, which shifts their maximum hardness. Always compare the exact composition when substituting.

Chemical Composition

Chemical composition, wt%

Element	SUS420J2 (JIS G4303)	1.4034 (EN 10088)	4Cr13 (GB/T 1220)
C	0.26–0.40	0.43–0.50	0.36–0.45
Si	≤1.00	≤1.00	≤0.60
Mn	≤1.00	≤1.00	≤0.80
P	≤0.040	≤0.040	≤0.040
S	≤0.030	≤0.030	≤0.030
Cr	12.00–14.00	12.5–14.5	12.00–14.00
Ni	≤0.60	-	≤0.60

Mechanical Properties and Hardness

In the soft-annealed condition the grade is machinable and formable. The values below are the specified minimums or maximums commonly stated for the annealed condition in the corresponding standards.

Mechanical properties, annealed condition

Property	SUS420J2	1.4034	4Cr13
Tensile strength, MPa	≥740	≥750	≥750
Yield strength, MPa	≥300	≥300	≥300
Elongation, %	≥15	≥12	≥12
Hardness, HBW	≤217	≤217	≤217

The value of this grade lies in its response to hardening. After oil or air quenching from the austenitizing range and tempering, hardness can reach approximately 50 HRC or higher depending on section size and tempering temperature. The exact response must be verified from the mill certificate and by hardness testing after heat treatment.

Heat Treatment

Typical practice is to austenitize at about 950–1010°C, quench in oil or air, and then temper between 150°C and 350°C to obtain the required hardness and relieve quenching stress. Higher tempering temperatures reduce hardness but improve toughness. Because the grade is air-hardening in thin sections, distortion control is important for precision parts. Always confirm the recommended cycle with the material supplier or a qualified heat treater for the specific product form and section.

Applications

420J2 is used wherever a combination of hardness, moderate corrosion resistance and low cost is required. Typical parts include knife blades and cutlery, scissors, surgical and dental instruments, shafts and spindles, valve seats and stems, plastic injection moulds, measuring tools and general wear parts. It is not intended for strongly corrosive or chloride-rich environments, where austenitic grades are required.

Frequently Asked Questions