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Stainless Steel - Grade 420 (UNS S42000)

Chemical Formula

Fe, <0.15% C, 12.0-14.0% Cr, <1.0% Mn, <1.0% Si, <0.04% P, >0.03% S

Topics Covered

Introduction
Key Properties
    Composition
    Mechanical Properties
    Physical Properties
    Grade Specification Comparison
    Possible Alternative Grades
Corrosion Resistance
Heat Resistance
Heat Treatment
Welding
Machining
Applications

Introduction

Grade 420 stainless steel is a high-carbon steel with a minimum chromium content of 12%. Like any other stainless steel, grade 420 can also be hardened through heat treatment. It offers good ductility in its annealed state and excellent corrosion resistance properties when the metal is polished, surface grounded or hardened. This grade has the highest hardness - 50HRC - among all the stainless steel grades with 12% chromium.

Stainless steel grades that are similar to grade 420 stainless steels include martensitic steels such as the other versions of grade 420, having vanadium, sulphur and molybdenum in their composition, and the grade 440 series. Non-standard grade 420C has carbon content that is little higher than that of grade 420.

Martensitic stainless steels are ones with high hardness and high carbon content. These steels are generally fabricated using methods that require hardening and tempering treatments. The operating conditions of martensitic steels are affected by loss of material’s strength at high temperatures, and decrease in ductility at negative temperatures.

Key Properties

The following properties are mentioned for bar products in ASTM A276. The specification may not necessarily be similar for other forms, such as forgings and plate.

Composition

The compositional ranges of grade 420 stainless steels are given in following table:

Table 1 - Compositional ranges of grade 420 stainless steels

Grade

C

Mn

Si

P

S

Cr

420

min.

max.

0.15

-

-

1

-

1

-

0.040

-

0.03

12.0

14.0

Mechanical Properties

The key mechanical properties of grade 420 stainless steels are tabulated below:

Table 2 - Mechanical properties of grade 420 stainless steels

Tempering Temperature (°C)

Tensile Strength (MPa)

Yield Strength
0.2% Proof (MPa)

Elongation (% in 50mm)

Hardness Brinell (HB)

Impact Charpy V (J)

Annealed *

655

345

25

241 max

-

204

1600

1360

12

444

20

316

1580

1365

14

444

19

427

1620

1420

10

461

#

538

1305

1095

15

375

#

593

1035

810

18

302

22

650

895

680

20

262

42

* Annealed tensile properties are typical for Condition A of ASTM A276; annealed hardness is the specified maximum.
# Tempering of this steel should be avoided in the range 425-600°C

Physical Properties

The table below provides the physical properties of grade 420 stainless steels in their annealed state:

Table 3 - Physical properties of annealed grade 420 stainless steels

Grade

Density (kg/m3)

Elastic Modulus (GPa)

Mean Coefficient of Thermal Expansion
(μm/m/°C)

Thermal Conductivity
(W/m.K)

Specific Heat 0-100°C
(J/kg.K)

Electrical Resistivity (nΩ.m)

0-100°C

0-315°C

0-538°C

at 100°C

at 500°C

420

7800

200

10.3

10.8

11.7

24.9

-

460

550

Grade Specification Comparison

The proximate grade specifications of 420 stainless steels are given in the table below: (These specifications are for functionally similar materials. Original specifications can be referred to for exact equivalents.)

Table 4 - Grade comparisons of grade 420 stainless steels

Grade

UNS No

Old British

Euronorm

Swedish SS

Japanese JIS

BS

En

No

Name

420

S42000

420S37

56C

1.4021

X20Cr13

2303

SUS 420J1

Possible Alternative Grades

The following table gives the suitable alternative grades to grade 420 stainless steels:

Table 5 Possible alternative grades of grade 420 stainless steels

Grade

Reasons for choosing grade 420

410

Only a lower hardened strength is needed.

416

High machinability is required, and the lower hardened strength and lower corrosion resistance of 416 is acceptable.

440C

A higher hardened strength or hardness than can be obtained from 420 is needed.

"Specials"

Variations of 420 are available to special order. These offer higher hardness, corrosion resistance and machinability for particular applications.

Corrosion Resistance

Under hardened conditions, grade 420 steels are resistant to fresh water, alkalis, air, foods and mild acids. The steel grades with a smooth surface finish have excellent performance. The corrosion resistance properties of grade 420 will tend to fall under annealed conditions. The corrosion resistance of grade 420 is lower than that of the grade 430 Ferritic alloys with 17% chromium, grade 410 steels and other austenitic grades.

This steel grade finds application in cutlery such as carving knives, table knives and so on. Grade 420 steels have good corrosion resistance against food, but continuous exposure of metals to unwashed food substances can lead to pitting corrosion.

Heat Resistance

Grade 420 stainless steels have a scaling resistance at temperatures of up to 650°C. However, temperatures above standard tempering temperature are not suitable for this grade.

Heat Treatment

Annealing – Grade 420 stainless steels can be heated at temperatures from 840 to 900°C, followed by slow furnace cooling at 600°C and then air-cooling.

Process Anneal – Grade 420 can be annealed at 735 to 785°C and air-cooled.

Hardening – This process involves heating grade 420 steels at 980 to 1035°C, followed by air or oil quenching. Oil quenching is usually preferred for heavy metal sections. Tempering is performed at 150 to 370°C to achieve high hardness and good mechanical properties. Grade 420 should not be tempered between 425 and 600°C.

Welding

Grade 420 stainless steels are welded using welding rods, coated with grade 420 metals, to achieve high-strength joints. During the process, steels are pre-heated at 150 to 320°C and post-heated to 610 to 760°C. In the “as welded” condition, parts are welded using grade 309 filler rods to achieve ductile joints. However, grade 309 electrodes or rods are recommended for welding grade 420 steels by AS 1554.6.

Machining

Grade 420 steels can be easily machined in their annealed state, but they are difficult to machine having a hardness greater than 30HRC. One of the most readily available machined alternatives is the free-machining grade 416 steels.

Applications

The key applications of grade 420 stainless steels include:

  • Shear blades
  • Needle valves
  • Surgical equipment
  • Cutlery

 

Date Added: Oct 23, 2001 | Updated: Apr 25, 2014
Comments
  1. Blu Krome Blu Krome United States says:

    Don't use 309 filler metal to weld onto ferritic steels. The carbon in the ferritic steel will be attracted to the higher chromium content in the 309 and during PWHT and service temps >800F the carbon will diffuse into the 309 and create a carbon-denuded zone at the fusion zone. The differences in the CTE will create a fatigue crack that will propagate along that narrow, carbon-denuded zone. When it breaks, and someday it will break, uninformed observers will swear it was a bad weld because it will look like lack of fusion. Not necessarily so; but definitely a poor choice of filler metal. If you want more ductility in the weld, use 410NiMo filler metal. Avoid austenitic/ferritic joints when possible, and when not possible then try to match the Cr contents and the CTEs. In such cases consider these filler metals: Inco 82/182, Hastelloy W, EPRI P87.

    • Joe McCrink Joe McCrink United States says:

      Will the Carbon migrate during welding as well as during the PWHT that you are discussing above? I regularly weld 410 SS in the hardened condition with 309L and see excessive corrosion in the HAZ about 1cm  away from the weld. Is there any correlation between what I'm seeing and what your discussing. Thanks

  2. Soubhagya Ranjan Soubhagya Ranjan United States says:

    My question is that here the carbon % is 0.15, which is coming under low carbon steel catagory. For this catagory heat treatment is not applicable but in above it is written that this 420-ss material is hardened by heat treatment. So kindly tell me how it is possible.

    Thanks,
    Soubhagya

    • Baljeet Poulastya Baljeet Poulastya India says:

      Mr. Soubhaya only carbon in the steel is not responsible for getting hardened.No doubt it is a low carbon grade but with very specific %age of Cr & Mn i.e. 12-14 & 1 respectively makes it a martensitic stainless steel.

    • William Richard William Richard United States says:

      The amount of chromium and nickel will affect hardness as well

  3. Anil Gupta Anil Gupta Nepal says:

    Dear Sir,

    We have imported Martensitic/ Magnetic stainless steel plate Grade. ASTM: UNS 41500/ Euronorms: 1.4313-X3CrNiMo13.4, size: 20x 1200x 2400 mm -- 4 nos. supplied by a shanghai based Chinese manufacturer.

    In this regard's we would like to acknowledge you that the materials has been carried out test from our end user. And found some serious issue as following.

    Chemical Test (%): C = 0.01, Mn = 0.4, Ni = 4.2 rest is same as per manufacturer test report. and quite acceptable.

    But we had a serious issue about mechanical test it found very bad as following.

    Mechanical Test: Y.S = 1172.334 N/mm2, UTS = 1114.494 N/mm2, El = 1.04 % only. Doesn’t match to manufacturer test report found very hard materials and Elongation is very low (please find attachment the mechanical test report from our end user).

    We don't understand that even the chemical test found satisfactory then why the mechanical test going wrong with the very high YS, UTS with very low elongation. Our end customer says that it may have poor manufacturing process during HRAP. (Hot rolled annealing pickled)

    They don't accept the materials as is it condition. Can you please advise us what we will may do to get the materials softer to get right % of elongation to obtain.

    Note: This steel plate is imported for maintenance job of fancies design hydro power turbine
    (Runner).

    Looking forward for your kind support.


    With Regard’s

    Anil Gupta (M.D)
    M/s. Project & Industrial Sales
    Hospital line, Butwal-10, NEPAL
    Email: anilguptaproject@gmail.com

  4. William Richard William Richard United States says:

    I would like to know how the forming process impacts the end product. I am currently using 420 that is turned, ground and polished. I am hoping to switch to coiled 420. Will I gain or lose attributes such as micro fractures, strength, or anything?
    Thanks,  Bill

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