GB 35CrMo Alloy Steel: Properties, Applications & Manufacturing Guide for Engineers

If you’re sourcing materials for high-stress parts in automotive, machinery, or construction, GB 35CrMo alloy steel is a reliable choice. As a Chinese standard low-alloy steel, it balances exceptional strength, toughness, and hardenability—making it perfect for components that can’t fail. This guide breaks down its key traits, real-world uses, and how to manufacture it, so you can make confident decisions for your projects.

1. Material Properties of GB 35CrMo Alloy Steel

GB 35CrMo’s performance is defined by its precise composition and inherent characteristics, all aligned with China’s GB/T 3077 standard (the official specification for this alloy).

1.1 Chemical Composition

The alloy’s elements work together to boost strength, durability, and heat resistance. Below is the standard composition range:

1.2 Physical Properties

These traits determine how GB 35CrMo behaves in real-world conditions (e.g., temperature changes or magnetic fields):

• Density: 7.85 g/cm³ (same as most ferrous alloys, so it’s easy to replace other steels in existing designs)
• Melting point: 1420 – 1450°C (high enough for high-temperature applications like industrial rollers or engine parts)
• Thermal conductivity: 43 W/(m·K) at 20°C (retains heat well, ideal for parts that operate continuously)
• Specific heat capacity: 465 J/(kg·K) at 20°C (stable heat absorption, preventing warping from sudden temperature swings)
• Thermal expansion coefficient: 12.1 μm/(m·K) (low expansion, critical for precision components like gears or shafts)
• Magnetic properties: Ferromagnetic (attracts magnets, useful for tools like magnetic clamps or sensors)

1.3 Mechanical Properties

GB 35CrMo’s full mechanical potential is unlocked through heat treatment (typically quenching + tempering). Below are typical values for the alloy in its optimized state, tested to Chinese standards:

1.4 Other Properties

• Corrosion resistance: Moderate (resists mild moisture and industrial oils; use zinc plating or paint for outdoor or humid environments)
• Wear resistance: Good (thanks to chromium (Cr) and heat treatment—suitable for moving parts like bearings or rollers)
• Machinability: Fair (softer in its annealed state; use high-speed steel (HSS) or carbide tools with cutting fluid to reduce tool wear)
• Weldability: Acceptable (preheat to 250 – 300°C and post-weld heat treat to avoid cracking; use low-hydrogen electrodes)
• Hardenability: Excellent (heat treatment penetrates deeply, ensuring uniform strength in thick parts like heavy machinery shafts)

2. Applications of GB 35CrMo Alloy Steel

GB 35CrMo’s mix of strength, toughness, and versatility makes it a top pick for high-stress applications across industries. Here are its most common uses, with real-world examples:

2.1 Automotive Industry

Cars, trucks, and commercial vehicles rely on parts that handle constant torque and impact. GB 35CrMo is used for:

• Shafts: A Chinese heavy-duty truck manufacturer uses it for drive shafts—its yield strength (≥835 MPa) handles 25-ton loads without bending.
• Gears: A domestic automaker uses it for transmission gears; the alloy’s fatigue strength (~520 MPa) extends gear life by 30% vs. carbon steel.
• Bolts and fasteners: High-performance pickup trucks use GB 35CrMo bolts for engine mounts—their tensile strength (≥980 MPa) resists vibration loosening.

2.2 Mechanical & Heavy Machinery

Industrial machines need parts that last through continuous use. GB 35CrMo is used for:

• Bearings: A manufacturing plant uses it for conveyor belt bearings—its wear resistance cuts maintenance downtime by 20%.
• Springs: A construction equipment maker uses it for excavator arm springs; the alloy’s elasticity (from tempering) withstands 8,000+ compression cycles.
• Rollers: Steel mills use it for rolling mill rollers; its hardness (229–286 HB) resists deformation from hot metal sheets.

2.3 Structural Components

For infrastructure and heavy-duty structures, GB 35CrMo provides reliable strength:

• Crane shafts: Port cranes use it for hoist shafts—its impact toughness (≥60 J) prevents fracture when lifting 40-ton containers.
• Bridge fasteners: Large-span highways use GB 35CrMo bolts; their corrosion resistance (with anti-rust coating) ensures long-term stability in outdoor conditions.

3. Manufacturing Techniques for GB 35CrMo Alloy Steel

To maximize GB 35CrMo’s performance, follow these proven manufacturing steps—aligned with industry best practices for low-alloy steels.

3.1 Steelmaking Processes

GB 35CrMo is typically produced using two methods:

• Electric Arc Furnace (EAF): Most common for medium batches. Scrap steel is melted with electrodes, then chromium (Cr) and molybdenum (Mo) are added to hit the target composition. EAF is flexible and reduces waste, making it ideal for custom orders (e.g., large shafts).
• Basic Oxygen Furnace (BOF): Used for large-scale production. Molten iron is mixed with oxygen to remove impurities, then alloying elements are added. BOF is faster and more cost-effective for mass-produced parts like bolts.

3.2 Heat Treatment

Heat treatment is critical to unlock GB 35CrMo’s full potential. The standard process for high-stress parts is:

1. Annealing: Heat to 820 – 850°C, cool slowly. Softens the alloy for easier machining (reduces tool wear by 35%).
2. Quenching: Heat to 830 – 850°C, cool rapidly in oil. Hardens the steel to reach tensile strength ≥980 MPa.
3. Tempering: Heat to 500 – 550°C, cool in air. Reduces brittleness while retaining strength—critical for parts like gears or shafts.
4. Nitriding (optional): Heat to 500 – 550°C in a nitrogen-rich atmosphere. Adds a hard outer layer (0.1–0.2 mm thick) to boost wear resistance (ideal for bearings).

3.3 Forming Processes

GB 35CrMo is shaped into parts using techniques that preserve its strength:

• Forging: Hammered or pressed at 1100 – 1200°C. Forging aligns the alloy’s grain structure, increasing tensile strength by 12% vs. cast parts. Used for gears, shafts, and crane components.
• Rolling: Passed through rollers to make bars, sheets, or rods. Used for basic shapes like bolts or spring blanks.
• Extrusion: Pushed through a die to make complex shapes (e.g., hollow shafts). Ideal for parts with tight tolerances, like automotive transmission components.

3.4 Machining Processes

After forming, parts are finished with precision machining:

• Turning: Uses a lathe to make cylindrical parts (e.g., shafts). Use cutting fluid (e.g., mineral oil) to prevent overheating and tool wear.
• Milling: Uses a rotating cutter to shape gear teeth or bearing races. Carbide tools are recommended for high precision (e.g., HRC 23–30 hardness).
• Drilling: Creates holes for bolts or fasteners. High-speed drills (900–1400 RPM) work best to avoid cracking.
• Grinding: Smooths surfaces to tight tolerances (e.g., ±0.01 mm for bearing inner rings). Improves wear resistance by reducing surface friction.

4. Case Study: GB 35CrMo in Industrial Conveyor Bearings

A Chinese manufacturing plant that produces steel pipes faced a problem: their carbon steel conveyor bearings failed every 3 months, causing costly production delays. They switched to GB 35CrMo—and solved the issue.

4.1 Challenge

The plant’s conveyors operated 24/7, moving hot steel pipes (up to 200°C) weighing 50 kg each. Carbon steel bearings had low wear resistance and heat stability, leading to frequent seizures and replacements.

4.2 Solution

They switched to GB 35CrMo bearings, using:

• Nitriding (520°C) to add a 0.15 mm hard outer layer for better wear resistance.
• Quenching (840°C) + tempering (530°C) to reach 850 MPa yield strength and 65 J impact toughness.
• Chrome plating to improve corrosion resistance in the plant’s humid environment.

4.3 Results

• Service life: Bearings now last 12 months—4x longer than before.
• Cost savings: Reduced maintenance costs by ¥120,000 per year (including labor and replacement parts).
• Reliability: Production downtime due to bearing failures dropped from 8 hours/month to 1 hour/month.

5. Comparative Analysis: GB 35CrMo vs. Other Materials

How does GB 35CrMo stack up against common alternatives? Below is a side-by-side comparison of key traits—helping you choose the right material for your project.

Key takeaway: GB 35CrMo matches 40Cr’s tensile strength but has better heat stability (thanks to molybdenum (Mo)), making it better for high-temperature applications. It’s cheaper than stainless steel and aluminum, making it the best value for high-stress, moderate-heat parts like conveyor bearings or truck shafts.

Yigu Technology’s Perspective on GB 35CrMo Alloy Steel

At Yigu Technology, GB 35CrMo is a staple in our product line for its reliability and versatility. We’ve supplied it to clients in automotive and machinery sectors for over 12 years, and its hardenability and fatigue strength consistently meet high-stress demands—from truck shafts to industrial bearings. We often recommend nitriding for wear-prone parts and anti-rust coatings for outdoor use, helping clients extend service life by 2–3x. For Chinese manufacturers seeking a cost-effective, high-performance alloy, GB 35CrMo remains an unbeatable choice.

FAQ About GB 35CrMo Alloy Steel

1. Can GB 35CrMo be used in high-temperature environments?

Yes—its melting point (1420–1450°C) and molybdenum (Mo) content let it perform reliably at temperatures up to 300°C. For higher temps (300–400°C), we recommend adjusting the tempering process (lower to 480–500°C) to boost heat stability.

2. What’s the difference between GB 35CrMo and GB 42CrMo?

GB 42CrMo has higher carbon (C) content (0.38–0.45% vs. 0.32–0.40% for GB 35CrMo), giving it 10% higher tensile strength. Choose GB 42CrMo for extreme-stress parts (e.g., 30-ton truck shafts), and GB 35CrMo for moderate-stress, cost-sensitive projects (e.g., conveyor bearings).

3. How to improve GB 35CrMo’s machinability?

Anneal the alloy first (heat to 820–850°C, cool slowly)—this softens it to 229–250 HB, making machining easier. Use carbide tools with cutting fluid (e.g., water-miscible coolant) and reduce cutting speed to 80–100 m/min to minimize tool wear.