42CrMo Alloy Steel Automotive Crankshaft

Product Overview

The crankshaft is the heart of any internal combustion engine, converting the linear reciprocating motion of pistons and connecting rods into rotational motion. Our precision forged and machined crankshafts are designed to withstand extreme mechanical and thermal stresses while maintaining dimensional stability and fatigue resistance. We offer both forged steel crankshafts for high-performance applications and cast crankshafts for standard automotive use.

All our crankshafts are custom manufactured based on customer drawings or samples. We work closely with automotive engine manufacturers to optimize crankshaft designs for strength, weight, and manufacturability. Every crankshaft undergoes precision CNC machining, induction hardening, and dynamic balancing to ensure reliable, smooth operation.

Material Options & Chemical Composition

We offer a wide range of steel and cast iron materials for crankshaft manufacturing:

Material Grade	Equivalent Standards	Key Properties	Typical Applications
42CrMo	AISI 4140, EN 1.7225, 42CrMo4	High strength, good toughness, excellent hardenability	Automotive, agricultural, industrial engines
35CrMo	AISI 4135, EN 1.7220	Good strength and toughness, weldable	Medium-duty engines, compressors
4130	AISI 4130, EN 1.7218, 25CrMo4	Good weldability, toughness, moderate strength	Racing engines, aircraft, high-performance
EN-GJS-700	ASTM A536 80-55-06, Ductile Iron	Good damping, cost-effective, castable	Passenger cars, light commercial vehicles
ADI (Austempered Ductile Iron)	EN-GJS-1400, ASTM A897	High strength, good fatigue, cost-effective	Automotive, heavy-duty engines
50CrMo4	AISI 4150, EN 1.7228	Very high strength, good fatigue resistance	Heavy-duty diesel engines, marine

Manufacturing Process

1. Raw Material Preparation

We source high-quality steel billets from certified suppliers. Each batch is verified with chemical analysis and ultrasonic inspection to ensure material quality and internal soundness before forging.

2. Forging

The crankshaft is forged using either open-die forging or closed-die forging depending on volume and complexity. Forging aligns the grain flow with the crankshaft geometry, significantly improving fatigue strength compared to machined-from-solid crankshafts.

3. Rough Machining

The forged crankshaft undergoes rough machining on CNC lathes and machining centers to remove excess material and establish basic dimensions. This includes turning of main journals and crank pins, and milling of counterweights.

4. Heat Treatment

Crankshafts undergo quenching and tempering to achieve the required mechanical properties. Typical heat treatment for 42CrMo includes austenitizing at 850-870°C, oil quenching, and tempering at 550-650°C to achieve 28-32 HRC.

5. Induction Hardening

Main journals and crank pins are induction hardened to 55-62 HRC for wear resistance. The hardened depth is carefully controlled to optimize the balance between surface hardness and core toughness. Fillet rolling may also be applied to improve fatigue strength.

6. Finish Machining

The crankshaft undergoes precision finish machining including grinding of all journal surfaces to Ra 0.4-0.8μm, milling of keyways, drilling of oil passages, and tapping of threaded holes. Tight tolerances of ±0.005mm are maintained on critical journal dimensions.

7. Dynamic Balancing

Every crankshaft undergoes two-plane dynamic balancing on precision balancing machines per ISO 1940 standards (G2.5 or G6.3 grade). Material is removed from counterweights as needed to achieve the required balance quality.

8. Surface Treatment & Inspection

Finished crankshafts undergo surface treatment (phosphating, painting, or anti-rust coating) and comprehensive quality inspection including dimensional CMM inspection, magnetic particle testing, ultrasonic testing, and hardness verification.

Quality Control & Testing

We maintain rigorous quality control at every stage of production to ensure that every crankshaft meets or exceeds customer specifications:

• Chemical Analysis: Spectrometer analysis of every heat, with full material test certificates (EN 10204 3.1)
• Mechanical Testing: Tensile strength, yield strength, elongation, impact, and hardness testing per ASTM A370 / ASTM E23
• Dimensional Inspection: CMM (Coordinate Measuring Machine) inspection of all critical dimensions and geometric tolerances
• Dynamic Balancing: Two-plane dynamic balancing per ISO 1940 (G2.5 or G6.3)
• Non-Destructive Testing (NDT): Magnetic particle testing (MT), ultrasonic testing (UT), liquid penetrant testing (PT)
• Hardness Testing: Rockwell hardness verification on journals and core material
• Surface Roughness: Surface roughness measurement on ground journal surfaces
• Ultrasonic Inspection: Full volume ultrasonic inspection for internal defects

Applications

Our crankshafts are used in a wide range of industries and applications:

• Automotive: Passenger cars, light trucks, commercial vehicles, buses
• Agricultural: Tractors, harvesters, irrigation pumps, farm equipment
• Construction: Excavators, bulldozers, cranes, concrete mixers
• Marine: Ship engines, boat engines, outboard motors, generators
• Power Generation: Diesel generators, standby power, cogeneration
• Industrial: Compressors, pumps, mining equipment, material handling
• Racing & Performance: Motorsports, high-performance engines, custom builds
• Motorcycles: Motorcycle engines, ATVs, snowmobiles, personal watercraft

Why Choose Huayong for Your Crankshafts?

• Complete In-House Capability: From forging to final CNC machining and balancing â€?all under one roof
• Material Expertise: Experienced in alloy steels, ductile iron, and ADI materials
• IATF 16949 & ISO 9001 Certified: Automotive-grade quality management system
• Induction Hardening: Precision induction hardening for wear-resistant journal surfaces
• Dynamic Balancing: Precision two-plane balancing for smooth engine operation
• Custom Manufacturing: All crankshafts made to your exact drawings and specifications
• Competitive Pricing: Factory-direct pricing with no middleman markup
• Fast Response: Quotations within 48 hours, technical support 24/7

Engineering Design Tips for Precision Castings

1. Wall Thickness Design

Maintain uniform wall thickness throughout the casting to minimize shrinkage porosity and thermal stress during solidification. Avoid abrupt section changes; use gradual transitions with fillet radii of at least 2-3mm. Minimum wall thickness for investment casting is typically 2mm for small parts and 3mm for larger components.

2. Draft Angles

Design with minimum 1° draft angle for external surfaces and 1.5° for internal surfaces to facilitate wax pattern removal from the die and ceramic shell breakdown. Deeper features may require additional draft.

3. Fillet Radii

Always use generous fillet radii at internal corners (minimum R2-3mm) to reduce stress concentration and improve castability. Sharp corners are prone to cracking and porosity during solidification.

4. Machining Allowance

Allow 2-3mm machining allowance per surface for CNC operations. Critical sealing surfaces and precision bores may require additional allowance. As-cast tolerances of ±0.1mm per 25mm are achievable with investment casting.

5. Surface Finish Considerations

Investment casting provides Ra 1.6-3.2μm as-cast surface finish. For applications requiring smoother surfaces, specify polishing, electropolishing, or machining in the drawing requirements.

Frequently Asked Questions

Q: What materials can you cast?

A: We work with stainless steel (304, 316, CF8, CF8M), carbon steel (WCB), alloy steel, duplex steel (2205), heat-resistant alloys, copper alloys, and specialty alloys. Custom compositions available per specification.

Q: What is the typical lead time?

A: Standard lead time is 30-45 days for production orders and 15-20 days for prototype/sample quantities. Rush service may be available depending on current production load.

Q: Can you provide material test certificates?

A: Yes, every heat comes with EN 10204 3.1 material test certificates including chemical composition and mechanical properties. Third-party inspection (Lloyd's, BV, SGS) available upon request.

Q: What is the minimum order quantity?

A: Our standard MOQ is 100 pieces, but we can accommodate smaller prototype orders with negotiable pricing. Tooling cost is amortized over production volume.

Q: Do you offer CNC machining services?

A: Yes, we provide complete in-house CNC machining including turning, milling, drilling, tapping, and grinding. We can deliver fully finished, ready-to-assemble components.