420 Round Bars / SS420 Bar / AISI 420 Bar / SAE 420 Bars

Product Description

AISI 420 Stainless Steel (Martensitic)

AISI 420 (also known as SS420 or SAE 420) is a high-carbon martensitic stainless steel. It is essentially a higher-carbon version of AISI 410, designed to be hardened through heat treatment to provide both high strength and excellent wear resistance.

In its hardened state, it achieves its peak corrosion resistance and can reach a hardness of up to 50 HRC.

International Designations & Equivalents

The 420 series is standardized globally, appearing under various regulatory frameworks:

Typical Chemical Composition

The carbon content determines the specific sub-grade (e.g., 420 "A" vs "B" vs "C"), which dictates the maximum achievable hardness.

• Chromium (Cr): 12.0% – 14.0%

• Carbon (C): 0.15% – 0.40% (depending on specific grade)

• Manganese (Mn): $\le$ 1.0%

• Silicon (Si): $\le$ 1.0%

• Iron (Fe): Balance

Mechanical Properties & Condition

AISI 420 round bars are typically supplied in the Annealed condition (Condition A) for easier machining, then hardened by the end-user.

Key Performance Attributes

• Corrosion Resistance: It is resistant to fresh water, mild acids, alkalis, and air. However, it is not suitable for marine environments or highly chloride-rich settings. It must be in the hardened and polished condition to achieve maximum resistance.

• Wear Resistance: Due to the high carbon content, it is highly resistant to abrasion and metal-to-metal wear.

• Magnetic Properties: Unlike 300-series (austenitic) stainless steels, AISI 420 is magnetic in all conditions.

• Machinability: Excellent in the annealed state. It is comparable to high-carbon tool steels but can become gummy if not handled with proper chip breakers.

Common Applications

AISI 420 round bars are preferred for components requiring a combination of high strength and moderate corrosion resistance:

1. Surgical & Dental Instruments: Used for forceps, scalpels, and needles due to its ability to hold a sharp edge and withstand sterilization.

2. Valves & Pumps: Ideal for needle valves, pump shafts, and internal valve trim where erosion resistance is critical.

3. Fasteners: High-strength bolts and nuts used in mildly corrosive industrial environments.

4. Cutlery: Professional-grade knife blades and shears.

5. Industrial Tooling: Bushings, shear blades, and plastic molds.

Processing Notes

• Welding: Generally not recommended due to its air-hardening characteristics. If welding is necessary, significant pre-heating (approx. 250°C) and post-weld annealing are required to prevent cracking.

• Heat Treatment: Harden at 980–1035°C followed by oil or air quenching. Tempering should be avoided in the 425–600°C range to prevent "temper embrittlement."