SteelWhat is 420 steel and what is it used for? Stainless steel for molds
420 stainless steel is a stainless mold steel. In this guide we explain what 420 stainless steel is, its chemical composition, hardness, how it is heat treated, what it is used for and the sizes we stock.
What is 420 stainless steel?
Hardenable high-chromium (~13%) martensitic stainless steel that combines good corrosion resistance with high hardness after quenching. Supplied annealed; quenches and tempers to 48–54 HRC. For injection molds for corrosive plastics, high-gloss molds and inserts.
Chemical composition of 420 stainless steel
This is the typical composition of 420 stainless steel (AISI 420 / EN-DIN 1.2083 / JIS SUS420J2 standard):
| Element | Contents | What for? |
|---|---|---|
| Carbon (C) | 0.36 – 0.42 % | Hardness and wear resistance |
| Silicon (Si) | 1.00 % max. | Deoxidizer |
| Manganese (Mn) | 1.00 % max. | Hardenability |
| Chromium (Cr) | 12.50 – 14.50 % | Corrosion and wear resistance |
| Phosphorus (P) | 0.030 % max. | Impurity, kept low |
| Sulfur (S) | 0.030 % max. | Impurity, kept low |
Hardness and heat treatment of 420 stainless steel
The typical working hardness of 420 is 48 – 54 HRC (quenched). It is supplied annealed and is quenched and tempered to 48–54 HRC. As a martensitic stainless steel (about 13 % chromium), it resists corrosion, ideal for corrosive plastics and high-gloss molds. You can see the full overview in our article on heat treatments for steel, and hardness scales in steel hardness.
What is it for? Applications of 420
420 stainless steel is mainly used in:
- Injection molds
- PVC molds
- Plastic molds
- Blow molds
- High-gloss molds
- Mold cavities
- Mold inserts
- Mold cores
- Extrusion dies
Forms and sizes we carry
At NAT MAC we stock 420 stainless steel in these forms and sizes:
| Package size | Sizes |
|---|---|
| Round bars | Ø 1" – 4" (Ø 25 – 102 mm) |
| Plates | 1/2" – 10" (13 – 254 mm) |
If you need a particular size, tell us which one and we will gladly source it for you.
420 equivalents and standards
420 stainless steel is also identified by these standards: AISI 420 / EN-DIN 1.2083 / JIS SUS420J2. You can see how to read them in our article on steel standards.
In summary
- 420 is a stainless steel for molds
- Typical composition: C 0.36 – 0.42 and Cr 12.50 – 14.50, plus alloying elements
- Typical working hardness: 48 – 54 HRC (quenched)
- Ideal for molds for corrosive plastics and high-gloss molds
- We carry it in round bar (1" – 4") and plates (1/2" – 10"), cut to size
Why buy your 420 stainless steel at NAT MAC?
We have more than 54 years of experience as an industrial supplier and ISO 9001 certified quality. We carry a wide range of tool grade steels and help you choose the right one for your tool or mold.
- Quality 420 Steel, backed and traceable
- Material cut to the size you need
- Technical advice on choosing the right grade
- Wide range of tool-grade steels in stock
- On-time deliveries and competitive prices
Tell us what tool or mold you are going to make and in what dimensions, and we will recommend the right grade and form. Request your free quote.
Sources: data sheet from our NAT MAC catalog (composition, sizes and applications) and public industry references for working hardness. Values are for reference and may vary by standard, heat and treatment.
