Reading this guide will provide you with specific information regarding 420 SS, its unique merits, equivalent SS, different properties, forms, etc.
Delve in for more information.
What is 420 Stainless Steel?
420 alloy is a martensitic type of SS. Another name for it is UNS 42000. In both states of annealing and hardening, it remains magnetic.
Another identifiable name of 420 alloy 1.4021.
What is 420 Stainless Steel Equivalent?
Alloy UNS 42000 is a martensitic, hardenable SS that represents an adjustment of 410 SS.
Compared to 410, 420 has 12-14% chromium content minimum. This affects their different levels of resisting corrosion.
Advantages of 420 Stainless Steel
- 420 SS is magnetic.
- Has reasonable corrosion resistance features. It has resistance to alkalis, freshwater, mild acid, food, air and to ammonia, carbonic acids, detergents, vinegar, steam, crude oil, dilutes nitric acids, etc.
- Welding is possible with welding rods used.
- Machining is easy when it is in its annealed state.
- With the right process, heat treatments are easy to go through with.
- It has the finest ductility when it is annealed. However, it can be hardened to 50 HRC minimum Rockwell hardness.
Disadvantages of 420 Stainless Steel
- Resistance is lowered when annealed.
- 420 SS is able to resist corrosion more only when it is hardened.
- It has poor welding characteristics.
420 Stainless Steel Properties
Chemical Properties
Welding
This SS comes with reduced welding features. This is because it has a hardened structure.
Corrosion Resistance
For high corrosion resisting levels, hardening is required.
Resistance to Heat
420 alloy comes with a maximum of 650°C scaling temperature.
Tempering is not ideal above 650°C.
Some other elements that make the chemical properties of 420 SS include:
- Carbon 0.16 – 0.25%
- Chromium 12 – 14%
- Silicon 1%
- Manganese 1.50%
- Sulphur 0.03%
- Phosphorous 0.04%
- Iron – balanced.
Physical Properties
- 1454 – 1510°C Melting Point
- Density 7.75 g/cm3
- 55 x 10ˆ-6Ω.m Electrical Resistivity
- 200 gpa Modulus of Elasticity in Tension
- 9 W/m.K Thermal Conductivity
- It is a magnetic alloy. 420 when heat treated and annealed shows magnetic porousness.
- 420 hardens with heat treatment.
Mechanical Properties
Temper – Hardened + 350°F
- 230,000psi minimum tensile strength
- Rockwell C55 hardness
- 8% elongation in 2”
- 195000 psi typical 2% yield strength
Temper – Annealed
- Rockwell B88 hardness
- 85000 psi minimum tensile strength
- 25% elongation in 2”
- 40000 psi yield strength min 0.2% offset.
Difference between 420 vs 440 Stainless Steel
| 420 | 440 | |
| Chemical composition | 1. Contains copper in its makeup.
2. Has up to 14% chromium. |
1. No copper in its makeup.
2. Has up to 18% chromium. |
| Hardness | 1. Soft
2. Easier to shape. |
1. Harder compared to 420.
2. Not so easy to shape. |
| Corrosion Resistance | 1. Resists corrosion. | 1. Higher chromium levels makes it more corrosion resisting compared to 420. |
| Resists heat. | 1. Low heat resistance.
2. Can deform when heat temperature is too high. |
1. Higher heat resistance.
2. Doesn’t deform easily at higher temperatures. |
| Price or Cost | Cheaper due to the less chromium element in its makeup. | Expensive due to high chromium percentage. |
| Electrical properties. | 1. 550 nano-ohm meters which is at 21OC.
2. Ideal for projects where low resistivity is required. |
1. 600 nano-ohm at 21OC.
2. Provides you with high resistivity. |
420 Fabricating and Machining Properties
Heat Treatment
Process Annealing – Heating should be done to 732-788°C. Then, air cooling initiated.
Annealing – Begin by heating slowing to 816-899°C. Follow up with furnace for slow cooling.
Hardening – Begin with preheating to 982 – 1066°C then oil quench or cool with air.
Follow by tempering or stress-relief.
Machining
The chip build-up that 420 creates is tough and stringy.
Although not entirely easy to machine, machining is a delight in their annealed state.
Welding
Due to air hardening features, welding is not easy with 420 ss. It is, however, possible after 300-400 F preheating.
Cold Working
It can withstand minor cold working. Strong forming methods will lead to cracks, however.
Designations of 420 Stainless Steel
The different designations of 420 SS include:
- 1.4021
- 1.4024
- 1.4028
- 1.4029
- 1.4030
- 1.4034
The Different Forms of 420 Stainless Steel
The different forms that 420 alloy comes in will mostly include bars, round bars, square, flats, hexagon bars, foils, coils, and so on.
Different Applications of 420 Stainless Steel
Also known as surgical steel, 420 is used for common applications like:
- Surgical tools and equipment
- Parts of washing machines.
- Cutlery
- Shear blades
- Hand tools
- Bolts and nuts
- Shafts (pump, and motor), etc.
Conclusion
The smooth nature of machining and also its magnetic features represents some of the reasons why you will find its use fulfilling.
Choose to invest in quality 420 alloy to ensure your applications turn out right.
More Resources:
Stainless Steel Composition – Source: Tuolian
Stainless Steel Grade 420 – Source: AZO Materials
Stainless Steel Grades – Source: Tuolian
