Multidimensional Classification Analysis of Stainless Steel Wheels

1. Classification Methods for Stainless Steel Wheels

Stainless steel wheels come in a wide variety. The Chinese standard GB/T 20878-2007 includes over 140 types, while in practical use, there are more than 200 types. Due to differences in composition, properties, and applications, stainless steels are classified in several ways, generally as follows:

(1) Classification by Main Chemical Elements
According to the primary elements or special alloying elements in the steel, stainless steels can be generally classified as:

• Chromium stainless steel (represented by Cr13 series)

• Chromium-nickel stainless steel (represented by Cr18Ni8 series)

• Chromium-nickel-molybdenum stainless steel

• Chromium-nickel-manganese stainless steel

• High-nitrogen stainless steel

• High-molybdenum stainless steel

(2) Classification by Metallographic Structure
This is the most traditional classification method. The microstructure of stainless steel is closely related to its chemical composition and heat treatment condition. Based on whether phase transformations occur during heating or cooling, and the main microstructure at room temperature, stainless steels are classified as:

• Martensitic stainless steel

• Austenitic stainless steel

• Ferritic stainless steel

• Austenitic-ferritic (duplex) stainless steel

(3) Classification by Carbon Content and Harmful Impurities
Based on carbon and harmful impurity content, stainless steels can be divided into:

• Standard stainless steel

• Low-carbon stainless steel

• Ultra-low-carbon stainless steel

• High-purity stainless steel

(4) Classification by Corrosion Resistance
Stainless steels may be categorized as:

• Stress corrosion-resistant stainless steel

• Pitting corrosion-resistant stainless steel

• Erosion-resistant stainless steel

(5) Classification by Service Environment
Based on the working medium and environment, stainless steels can be categorized as:

• Nitric acid-resistant stainless steel

• Sulfuric acid-resistant stainless steel

• Urea-resistant stainless steel

• Seawater-resistant stainless steel

(6) Classification by Economized Alloying Elements
Due to the cost and scarcity of certain elements, many countries have developed grades that minimize the use of expensive alloying elements, such as:

• Nickel-saving stainless steel

• Nickel-free stainless steel

• Chromium-saving stainless steel (e.g., steels where silicon or aluminum substitutes part of the chromium)
  Typical examples include Cr-Mn-N and Cr-Mn-Ni-N stainless steels.

(7) Classification by Special Alloying Elements
Based on specific alloying elements, stainless steels can be classified as:

• High-silicon stainless steel

• High-molybdenum stainless steel

• High-nitrogen stainless steel

(8) Classification by Functional Characteristics
According to functional properties, stainless steels can be categorized as:

• Cryogenic and ultra-low-temperature stainless steel

• Non-magnetic stainless steel

• High-strength stainless steel

• Superplastic stainless steel

• Free-machining stainless steel

• Heat-resistant stainless steel

2. Classification Method in National Standards

According to GB/T 13304.1-2008, stainless steels are divided into five major categories based on their metallographic structure:

(1) Austenitic Stainless Steel
Mainly consists of austenitic structure with face-centered cubic (FCC) crystal structure (γ phase). These steels are non-magnetic but may develop slight magnetism after cold working. They are primarily strengthened through cold deformation.

(2) Ferritic Stainless Steel
Mainly consists of ferritic structure with body-centered cubic (BCC) crystal structure (α phase). These steels are magnetic and cannot be hardened by heat treatment but can be slightly strengthened through cold working.

(3) Austenitic-Ferritic (Duplex) Stainless Steel
Contains both austenitic and ferritic structures, with the minor phase typically accounting for more than 15% by mass. These steels are magnetic and can be strengthened through cold working.

(4) Martensitic Stainless Steel
Has a martensitic structure, is magnetic, and its mechanical properties can be adjusted through heat treatment.

(5) Precipitation-Hardening Stainless Steel
The base structure is austenitic or martensitic. These steels can be hardened (strengthened) through precipitation hardening (also known as aging treatment), and are commonly used for forged stainless steel wheel components.