Steel Alloy Guide

Steel Grade 1XXX

Here’s the detailed comparison of the common carbon steels (1010, 1018, 1020, 1040, 1045, 1050, 1065) in terms of composition, mechanical properties, and typical applications:

Chemical Composition (Key Difference: Carbon Content)

Mechanical Properties Comparison

Heat Treatment Response

Typical Applications and Selection Guide

Steel Grade 4XXX

Here’s a detailed comparison of 4130, 4140, and 4150 chromium-molybdenum alloy steels (Chromoly Steel), covering composition, properties, heat treatment, and applications:

Chemical Composition Comparison (Key Differences: Carbon Content & Alloy Ratios)

Mechanical Properties & Heat Treatment

• 4130:
  • Moderate strength (tensile strength ~850 MPa after quenching/tempering) with excellent toughness.
  • Heat treatment: Typically normalized or quenched + tempered; post-weld stress relief required.
  • Applications: Aircraft structures, race car chassis, hydraulic components.
• 4140:
  • High strength (tensile strength ~1000 MPa after heat treatment) with superior wear resistance.
  • Heat treatment: Hardness reaches HRC 28-32 after quenching + tempering; can be surface-hardened (e.g., nitriding).
  • Applications: Heavy-duty shafts, gears, drilling tools, molds.
• 4150:
  • Ultra-high strength (tensile strength ~1100 MPa) but lower ductility.
  • Heat treatment: Requires controlled quenching to avoid cracking; tempered hardness HRC 35-50.
  • Applications: High-strength springs, firearm components, impact tools.

Key Differences Summary

Selection Guidelines

• Welding + balanced strength: Choose 4130 (e.g., aircraft frames, welded structures).
• High load + wear resistance: Opt for 4140 (e.g., gears, heavy shafts).
• Extreme hardness/wear: Select 4150 (e.g., military components, high-performance springs).

Additional Notes

• 4140 vs. 4150: 4150’s higher carbon content suits extreme hardness needs but sacrifices toughness compared to 4140.
• Alternatives: For better impact resistance, consider 4340 (nickel-added, superior toughness).

Steel Q Series

Here’s a detailed comparison of Q235, Q345, and Q355 structural steels under Chinese standards (GB/T), covering composition, mechanical properties, and applications:

Basic Information & Standards

• Q235
  • Standard: GB/T 700-2006 (Carbon Structural Steel)
  • Old Designation: A3 (obsolete)
• Q345
  • Standard: GB/T 1591-2008 (High-Strength Low-Alloy Structural Steel)
  • Old Designation: 16Mn (obsolete)
• Q355
  • Standard: GB/T 1591-2018 (Replaces Q345)
  • International Equivalent: Similar to EN S355 or ASTM A572 Gr.50

Chemical Composition (Key Differences)

Mechanical Properties

Q355 vs Q345:

• Higher yield strength (355MPa vs 345MPa) with same tensile range.
• Better low-temperature toughness (stricter control of P/S content).

Typical Applications

• Q235:
  • Low-strength structures: rebar, guardrails, general bolts.
  • Not recommended for critical welded parts (no alloy strengthening).
• Q345:
  • Bridges, ships, pressure vessels, construction machinery (welded medium-high strength structures).
  • Being phased out by Q355 (new designs should use Q355).
• Q355:
  • High-rise buildings, wind turbine towers, heavy machinery (high-load & low-temperature environments).
  • Preferred for international projects (compatible with EN S355).

Key Differences Summary

Selection Guide

• Low-cost static structures: Q235 (e.g., non-load-bearing frames).
• Traditional welded structures: Q345 (for legacy projects or budget constraints).
• New designs/high demands: Always choose Q355 (superior strength, toughness, and global compatibility).

Important Notes

• Q345 phase-out: GB/T 1591-2018 replaced Q345 with Q355, though old stock may remain.
• European equivalents: Q355 ≈ S355J2 (EN). Confirm exact grade requirements for exports.

A2 Steel

Here’s a detailed technical breakdown of A2 Tool Steel properties and characteristics:

Classification: Air-hardening medium-alloy cold work tool steel (ASTM A681)

Chemical Composition (Key Elements)

Key Material Properties

• Hardness Range: HRC 58-62 (after proper heat treatment)
• Wear Resistance: Excellent (superior to oil-hardening steels)
• Toughness: Good for its hardness level (better than D2 steel)
• Dimensional Stability: Minimal distortion during heat treatment
• Corrosion Resistance: Moderate (better than carbon steels but requires protection)

Heat Treatment Guidelines

Annealing:

• Process: Heat to 850-870°C (1562-1598°F), slow cool to 500°C (932°F), then air cool
• Resultant Hardness: ~200 HB

Hardening:

• Austenitizing: 940-980°C (1724-1796°F)
• Quenching: Air cooling (primary method) or oil quenching
• Achievable Hardness: HRC 60+ (as-quenched)

Tempering:

• Recommended Range: 175-250°C (347-482°F) for maximum hardness
• Alternative: 400°C+ (752°F+) for increased toughness (reduced hardness)

Typical Industrial Applications

• Tooling: Blanking dies, forming dies, trim dies
• Cutting Tools: Shear blades, slitter knives, woodworking tools
• Precision Components: Gauges, machine parts requiring stability
• Specialty Uses: Food processing equipment (when properly polished)

Comparative Analysis with Similar Tool Steels

Advantages and Limitations

Advantages:

• Superior dimensional stability during heat treatment
• Balanced combination of wear resistance and toughness
• Air-hardening capability reduces quenching stresses
• Good machinability in annealed condition

Limitations:

• Requires corrosion protection for humid environments
• Not suitable for high-temperature applications (>400°C)
• Grinding can be challenging at full hardness

Material Selection Guidance

• For extreme wear applications: Consider D2 steel (higher chromium)
• When corrosion resistance is critical: 440C stainless steel alternative
• For complex geometries: A2 is preferred due to minimal heat treatment distortion
• Budget-conscious projects: O1 steel may offer cost savings

Note: For optimal performance, always specify:

• Required hardness range
• Surface finish requirements
• Corrosion protection needs
• Post-machining treatments

12L14 Steel

Here’s a detailed technical specification of 12L14 Steel, a free-machining leaded steel:

Classification: Low-carbon, leaded free-machining steel (ASTM A29)

Chemical Composition

Key Material Properties

• Machinability Rating: 85% (compared to 1215 steel as 100% benchmark)
• Tensile Strength: 540 MPa (can reach 700 MPa with cold working)
• Hardness: HRB 85-100 (annealed condition)
• Surface Finish: Excellent (minimal post-machining polishing required)
• Weldability: Poor (not recommended for welded applications)

Heat Treatment & Processing

• Non-hardenable: Cannot be strengthened by heat treatment
• Cold Working: Only practical method for increasing strength
• Annealing: 650-700°C (1200-1300°F) to relieve stresses
• Recommended Cutting Speed: 100-150 m/min (300-500 SFM) for turning

Typical Applications

• High-volume turned parts: Screws, bolts, nuts, fittings
• Precision components: Electrical connectors, terminals
• Small mechanical parts: Watch components, firearm accessories
• Non-structural uses: Bushings, spacers, knobs

Comparison with Other Free-Machining Steels

Advantages and Limitations

Advantages:

• Industry-leading machinability for high-speed production
• Superior surface finish quality
• Extended tool life (2-3× longer vs. non-free-cutting steels)
• Excellent for complex, precision-turned components

Limitations:

• Limited mechanical properties (not for structural applications)
• Lead content restricts use in food/medical applications
• Poor weldability and formability
• Not suitable for heat treatment

Material Selection Guidance

• For RoHS compliance: Consider 11SMnPb30 (lead-free alternative)
• When higher strength needed: 1144 stress-proof steel
• For best machining performance: 12L14 remains top choice

Processing Notes:

• Use sharp, positive-rake tools
• Avoid heavy cuts at low speeds
• Chip breakers recommended for continuous machining
• Proper ventilation required due to lead content

High Ccarbon High Alloy Mold Steel

Here is a concise English translation of the detailed comparison of the four high-carbon, high-alloy mold steels (Cr12, SKD11, S7, and A2):

Basic Classification and Standards

Chemical Composition Comparison (Key Elements)

Core Performance Comparison

Typical Applications

• Cr12:
  • High-load stamping and drawing molds (e.g., silicon steel sheet punching)
  • Not recommended for impact conditions (high risk of brittleness)

• SKD11
  • Precision blanking molds, thread rolling dies, cutting tools (preferred Japanese alternative to D2)
  • uitable for applications requiring a balance of wear resistance and moderate toughness
• S7
  • Impact tools (chisels, hammers), hot work molds (e.g., die casting insert blocks)
  • High-toughness applications (e.g., repeated impact)
• A2:
  • Complex-shaped cold work molds, precision gauges (e.g., gages)
  • Precision components requiring minimal heat treatment distortion

Heat Treatment Key Points

• Cr12/SKD11: Quenching temperature: 980-1050°C (oil quenching), high-temperature tempering (above 500°C) required to reduce brittleness
• S7: Quenching temperature: 930-955°C (air or oil quenching), tempering temperature 200-400°C
• A2: Quenching temperature: 940-980°C (air hardening), tempering 175-250°C

Selection Suggestions

• Extreme wear resistance + low impact → Cr12 (but design to prevent cracking)
• Wear resistance + moderate toughness → SKD11 (superior comprehensive performance to Cr12)
• High impact load → S7 (sacrifices some wear resistance)
• Precision molds + low distortion → A2 (significant air-hardening advantage)

Additional Notes

• SKD11 vs. Cr12: SKD11 improves toughness over Cr12 by adding molybdenum/vanadium to refine grain size.
• Environmental Alternatives: For chromium-free options, consider high-speed steels (e.g., M2) or powder metallurgy steels (e.g., ASP-23).

High Speed Ttool Steel

Here’s a professional comparison of SKH9, M2, H11, and H13 high-speed tool steels and hot-work die steels:

Classification & Positioning

Performance Radar Chart (5-point scale)

            Thermal Resistance
              ↗-----↖
Red Hardness ★★★★★ | SKH9/M2 | Wear Resistance ★★★★★
          ★★★☆ |  H11   | ★★★☆
          ★★★★ |  H13   | ★★★★
              ↖-----↙
              Toughness

Note: SKH9/M2 for cutting, H11/H13 for hot-work applications

Composition & Microstructure

Operational Limits

Test condition: 600°C↔water quenching until cracking

Failure Mode Analysis

• SKH9/M2 Tools:
  ▸ Main failure: Crater wear
  ▸ Solution: Apply AlCrN coating
• H13 Dies:
  ▸ Main failure: Heat checking
  ▸ Improvement: Optimize mold temperature uniformity

Technological Advances

• Powdered SKH9: Grain size up to ASTM 12 (vs 8-10 conventional)
• Nano-coated H13: TD (VC) treatment extends life 3-5x
• M2 Alternative: PM HSS (e.g., ASP2030) for precision tools

Selection Decision Tree

Cutting application required?
├─ Yes → Need extreme red hardness?
│   ├─ Yes → Choose SKH9/M2
│   └─ No → Consider cost-effective HSS (e.g., M35)
└─ No → Operating temp >500°C?
    ├─ Yes → Select H13
    └─ No → Choose H11 (lower cost)

Key Differentiators

• SKH9 vs M2:
  ▸ SKH9 has stricter S/P control (≤0.025%)
  ▸ M2 has wider quenching range (1210-1240°C vs SKH9’s 1220-1230°C)
• H13 Enhancements:
  ▸ ESR-refined H13: 30% better isotropy
  ▸ Nb-modified H13 (0.06%Nb): 2x thermal fatigue life

Mold Steel

Here is the detailed comparison and analysis of the mold steels 3Cr2Mo (P20), 718, S136, 4Cr13, and 3Cr13:

Basic Classification and Standards

Chemical Composition Comparison (Key Elements)

Core Performance Comparison

Typical Applications

• 3Cr2Mo (P20):
  • General plastic molds (ABS/PP), low-demand die casting molds
  • Features: Low cost, direct machining possible (no heat treatment required)
• 718:
  • High-gloss plastic molds (PC/PMMA), medium-sized die casting molds
  • Features: 2-3 times longer life than P20
• S136:
  • Transparent part molds (lenses, medical devices), corrosive environments
  • Features: Mirror finish polishable to Ra ≤ 0.01μm
• 4Cr13/3Cr13:
  • Medical instruments, food molds (rust prevention with limited budget)
  • Differences: 4Cr13 is harder, 3Cr13 is more impact-resistant

Heat Treatment and Machinability

Selection Decision Guide

Do you need corrosion resistance?
├─ Yes → Do you need mirror finish?
│   ├─ Yes → Choose S136
│   └─ No → Choose 4Cr13/3Cr13 (depending on hardness requirements)
└─ No → What is the mold life requirement?
    ├─ <500,000 cycles → P20 (most economical)
    ├─ 500,000-3,000,000 cycles → 718
    └─ >3,000,000 cycles → Consider H13 or other advanced materials

Cost and Life Balance

Special Notes

• Differences between 718 and P20:
  • 718 adds nickel, improving thermal fatigue resistance by 30%
  • 718 has lower sulfur content (≤0.001% vs P20’s ≤0.005%), resulting in better polishability
• Alternatives to S136:
  • Cost-effective: German 1.2083 (X40CrMoV15)
  • High-end: Japanese PD613 (super mirror finish)
• Stainless Steel Selection:
  • 4Cr13 is suitable for high-hardness rust prevention applications (e.g., surgical instruments)
  • 3Cr13 is suitable for rust prevention parts that require bending (e.g., cutlery molds)

Bearing Steel

Detailed Characteristics of GCr15 Bearing Steel

GCr15 is the most commonly used high-carbon chromium bearing steel in China (equivalent to the international standard SAE 52100). It is specifically designed for rolling bearings, featuring high hardness, excellent wear resistance, and good fatigue life. Below are its key characteristics:

Chemical Composition (%)

Core Performance

• Hardness: After quenching and low-temperature tempering: HRC 61-65
• Wear Resistance: High carbon content and chromium carbides provide excellent rolling wear resistance.
• Contact Fatigue Life: Capable of withstanding over 10⁷ cycles of cyclic loading (superior to ordinary high-carbon steels).
• Dimensional Stability: Minimal deformation after low-temperature tempering (150-180°C), suitable for precision bearings.

Heat Treatment Process

• Spheroidizing Annealing (Pre-treatment):
  • Temperature: 790-810°C → slow cooling to 700°C → furnace cooling to 600°C, then remove from furnace.
  • Objective: To achieve spheroidal pearlite (hardness ≤207 HB) for easy machining.

• Quenching:
  • Temperature: 830-850°C (oil quenching or salt bath quenching).
  • Microstructure: Martensite + residual austenite (5-10%) + undissolved carbides.

• Tempering:
  • Temperature: 150-180°C (hold for 1-2 hours).
  • Purpose: To relieve stress, stabilize dimensions, and maintain high hardness.

Typical Applications

• Rolling Bearings: Inner and outer rings, balls, rollers (e.g., automotive wheel hub bearings).
• Precision Parts: Gauges (gauge blocks), machine tool spindles, hydraulic pump rotors.
• Tools: Cold stamping dies, cutting tools (applications requiring high wear resistance).

Comparison with Other Bearing Steels

Machining and Precautions

• Machinability: Good machinability in the annealed state, but grinding is required after quenching.
• Weldability: Very poor (high carbon content leads to a tendency for cold cracking, welding is not recommended).
• Rust Prevention: Chromium plating or phosphating is required (chromium content is insufficient for rust prevention).

Failure Modes and Improvements

• Common Failures:
  • Contact fatigue spalling (surface-originated).
  • Solution: Increase material purity (e.g., vacuum degassing during smelting).
• Upgraded Version:
  • GCr15SiMn: Addition of Si/Mn, suitable for larger-sized bearings (enhanced hardenability).

International Equivalents and Selection

• US Standard: SAE 52100 (almost identical composition)
• European Standard: 100Cr6 (EN ISO 683-17)
• Japanese Standard: SUJ2 (JIS G4805)

Selection Suggestions:

• For conventional bearings: Prioritize GCr15 (best cost-performance ratio).
• For large-sized/high-load bearings: Choose GCr15SiMn.
• For high-temperature environments: Select M50 or CSS-42L (cobalt-based alloy).

Alloy Structural Steel

Basic Classification and Standards

Chemical Composition Comparison (Key Elements)

Mechanical Properties Comparison (After Quenching and Tempering)

Heat Treatment Process

Typical Applications

• 40Cr: Shafts, gears, bolts (e.g., automotive half-shafts) — Best cost-performance ratio
• 35CrMo: Petroleum drilling tools, high-temperature bolts (operating temperature ≤500°C)
• 42CrMo: Heavy machinery gears, connecting rods, high-pressure valves (high-load components)
• 40CrNiMo: Aircraft engine crankshafts, armor plates (extreme impact environments)
• 38CrMoAl: Precision screws, machine tool spindles (surface hardness ≥1100 HV after nitriding)

Key Properties Comparison

Selection Decision Tree

Do you need ultra-high surface hardness?
├─ Yes → Choose 38CrMoAl (nitriding treatment)
└─ No → Type of load?
    ├─ Static/medium load → 40Cr (economical)
    ├─ Dynamic load/medium-high temperature → 35CrMo/42CrMo
    └─ Extreme impact → 40CrNiMo

Special Notes

• 42CrMo vs 40CrNiMo: 40CrNiMo has significantly better low-temperature toughness (-40°C) due to its nickel content compared to 42CrMo.
• Nitriding Advantage of 38CrMoAl: Nitriding layer depth 0.3-0.5mm, surface hardness ≥65 HRC, improved corrosion resistance.
• Alternative Materials: For higher heat resistance: Choose 34CrNiMo6 (European standard, operating temperature ≤550°C).

Fatigue Life Comparison (10⁷ cycles stress):
40CrNiMo > 42CrMo > 35CrMo > 38CrMoAl > 40Cr

Spring Steel

Here’s a detailed comparison of the two spring steels, 65Mn and 60Si2Mn:

65Mn

Composition Characteristics

• Main Elements: Carbon (0.62%~0.70%), Manganese (0.90%~1.20%). A high-carbon manganese steel with minimal silicon (Si) content.
• Alloy Simplicity: Relies on manganese for hardenability enhancement.

Mechanical Properties

• Hardness & Strength:
• After quenching + tempering: HRC 45-55, tensile strength 800-1000 MPa.
• High elastic limit but lower than 60Si2Mn.
• Toughness: Relatively low; prone to brittleness under high stress or low temperatures.

Processing Characteristics

• Heat Treatment:
• Moderate hardenability; critical oil-quenching diameter ~15-20mm (water quenching risks distortion/cracking).
• Tempering range: 400-500°C (produces troostite structure).
• Machinability: Poor cold-forming properties; usually requires hot forming or annealing.

Typical Applications

• Low-cost springs (e.g., clutch springs, brake springs), agricultural tools, small leaf springs.
• Suitable for low-to-medium stress applications with no stringent fatigue life requirements.

60Si2Mn

Composition Characteristics

• Main Elements: Carbon (0.56%~0.64%), Silicon (1.50%~2.00%), Manganese (0.60%~0.90%).
• Role of Silicon: Enhances elastic limit, tempering stability, and delays decarburization.

Mechanical Properties

• Hardness & Strength:
• After quenching + tempering: HRC 45-55, tensile strength 1000-1200 MPa.
• Higher elastic limit and better anti-relaxation properties than 65Mn.
• Toughness: Improved due to silicon, but large sections may still exhibit brittleness.

Processing Characteristics

• Heat Treatment:
• Superior hardenability; critical oil-quenching diameter ~25-30mm.
• Tempering range: 450-520°C (silicon resists temper softening).
• Machinability: Good hot-forming performance, but silicon increases decarburization risk (controlled heating atmosphere required).

Typical Applications

• High-stress springs (e.g., automotive leaf springs, heavy-duty machinery), safety valve springs.
• Ideal for large cross-sections or applications demanding high fatigue resistance.

Comparison Summary

Material Selection Guide

• Choose 60Si2Mn for: High fatigue life, anti-relaxation needs, or larger cross-sections.
• Opt for 65Mn when: Cost is critical, or for low-stress/small components with simple processing.

Note: Both steels are susceptible to temper embrittlement (250-400°C range); rapid cooling after tempering is recommended.