In mechanical engineering courses, there are usually subjects such as Engineering Materials or Metal Processing Technology. The main purpose of these courses is to teach us how to choose materials correctly in mechanical design. Good material selection not only considers the material’s performance but also its cost-effectiveness. However, in many cases, some commonly used materials can meet most machining needs. For example, 45 steel and Q235 are widely used, but what are the actual differences between these commonly used materials? Understanding these differences will make you more confident and professional in material selection. Therefore, it is highly recommended to read through this article.
1. 45 Steel - High-Quality Carbon Structural Steel, the Most Common Medium Carbon Alloy Steel
- Main Characteristics:
- The most commonly used medium carbon heat-treated steel with good overall mechanical properties.
- Low hardenability; prone to cracking when quenched in water.
- Small parts should be treated by tempering, while larger parts should be normalized.
- Application Example:
- Used to manufacture high-strength moving parts such as turbine blades, compressor pistons, shafts, gears, racks, worm gears, etc.
- For welded parts, preheating before welding is necessary, and stress relief annealing is required afterward.
2. Q235A (A3 Steel) - The Most Common Carbon Structural Steel
- Main Characteristics:
- High plasticity, toughness, and weldability, good cold stamping performance, and certain strength.
- Excellent cold bending performance.
- Application Example:
- Widely used for parts and welded structures with general requirements, such as rods, connecting rods, pins, shafts, screws, nuts, rings, brackets, machine beds, building structures, bridges, etc.
3. 40Cr - One of the Most Widely Used Alloy Structural Steels
- Main Characteristics:
- After heat treatment, it has good overall mechanical properties, low-temperature impact toughness, and good hardenability.
- Oil quenching provides higher fatigue strength, while water quenching can easily cause cracking in complex-shaped parts.
- Good cutting performance after tempering or heat treatment, but poor weldability.
- Preheating is required before welding (100-150°C).
- Application Example:
- After heat treatment, it is used to manufacture medium-speed, medium-load parts such as machine tool gears, shafts, worm gears, spline shafts, etc.
- After tempering and high-frequency surface hardening, it is used for manufacturing parts with high surface hardness and wear resistance, such as gears, shafts, spindles, crankshafts, and valve seats.
4. HT150 - Gray Cast Iron
- Application Example:
- Gearboxes, machine tool beds, housings, hydraulic cylinders, pump bodies, valve bodies, flywheels, cylinder heads, pulleys, bearing caps, etc.
5. 35 Steel - Common Material for Various Standard Parts and Fasteners
- Main Characteristics:
- Appropriate strength, good plasticity, high cold plasticity, and reasonable weldability.
- Low hardenability; used after normalizing or heat treatment.
- Application Example:
- Suitable for manufacturing small cross-section parts that can bear larger loads, such as crankshafts, levers, connecting rods, hooks, rings, and all types of standard parts and fasteners.
6. 65Mn - Common Spring Steel
- Application Example:
- Small-sized flat and round springs, seat springs, clock springs, spring rings, valve springs, clutch springs, brake springs, cold-wound spiral springs, snap rings, etc.
7. 0Cr18Ni9 - The Most Common Stainless Steel (Equivalent to U.S. Steel No. 304 and Japanese Steel No. SUS304)
- Characteristics and Application:
- Most widely used as stainless heat-resistant steel, such as for food equipment, general chemical equipment, and energy industry equipment.
8. Cr12 - Common Cold Work Tool Steel (Equivalent to U.S. Steel No. D3 and Japanese Steel No. SKD1)
- Characteristics and Application:
- Cr12 is a widely used cold work tool steel with high carbon and high chromium content.
- It has good hardenability and wear resistance but is brittle due to its high carbon content.
- Cr12 steel is used for manufacturing cold punching molds, punches, die molds, cold-heading molds, cold-extrusion molds, and other tools.
9. DC53 - Common Japanese Imported Cold Work Tool Steel
- Characteristics and Application:
- High-strength, tough cold work tool steel, manufactured by Daido Steel (Japan).
- After tempering, it has high hardness and toughness, and good wire-cutting properties.
- Used in precision cold stamping molds, stretch molds, threading dies, cold cutting dies, punches, etc.
10. SM45 - Common Carbon Plastic Mould Tool Steel (Equivalent to Japanese Steel No. S45C)
- Application Example:
- Used in general plastic molds.