EN8D Round Bars: Complete Technical Guide & Industrial Applications
Overview: What Are EN8D Round Bars?
In India, EN8D is a widely used medium-carbon engineering steel trade designation with chemical composition and properties broadly comparable to BS 970 080M40, EN 10083-2 C40, and AISI/SAE 1040. Composition and properties can vary slightly by mill, so treat these as close equivalents, not identical grades. EN8D is chosen when you need a balance of toughness, strength and machinability for shafts, fasteners and general machinery.
Ambhe Ferro Metal Processors Private Limited supplies high-quality EN8D round bars in 23.5 mm to 80 mm diameter for automotive, engineering, and manufacturing applications across India.
Technical Specifications
Chemical Composition of EN8D (typical limits)
| Element | Percentage (%) | Purpose & Impact |
|---|---|---|
| Carbon (C) | 0.40 – 0.45 | Provides strength and hardenability |
| Silicon (Si) | 0.10 – 0.40 | Improves strength and deoxidation |
| Manganese (Mn) | 0.70 – 0.90 | Enhances hardenability and tensile strength |
| Phosphorus (P) | 0.045 max | Lower P improves toughness and ductility |
| Sulphur (S) | 0.045 max | Controlled for toughness; can aid machinability |
| Chromium (Cr) | 0.20 max (residual) | Residual content; minor grain/refinement effects |
| Nickel (Ni) | 0.30 max (residual) | Residual content; contributes to toughness |
Physical & Mechanical Properties
| Property | Typical Value | Testing Standard |
|---|---|---|
| Tensile Strength | 550– 700 N/mm² | IS 1608 / ASTM E8 |
| Yield Strength | ≥ 365 N/mm² | IS 1608 / ASTM E8 |
| Elongation | ≥ 16% (on 5.65√So) | IS 1608 / ASTM E8 |
| Reduction of Area | ≥ 35% | — |
| Hardness | ~170 – 210 BHN | IS 1500 / ASTM E10 |
| Impact Strength | ≥ 34 J (Charpy V, RT) | — |
| Modulus of Elasticity | ~210 GPa | — |
| Density | ~7.85 g/cm³ | — |
Note: Mechanical properties vary with section size and processing; larger diameters can show lower UTS/YS.
After Heat Treatment (Q&T)
- Tensile Strength: up to ~1000 N/mm² (section & temper dependent)
- Yield Strength: up to ~700 N/mm²
- Hardness: ~250 – 320 BHN (typical engineering range)
- Fatigue performance: can improve substantially with appropriate Q&T and surface finish (quantify via component testing)
Available Sizes and Dimensions
Standard Size Range (Ambhe Ferro Metal Processors Private Limited)
Hot Rolled Sizes : 23.5mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, 38mm, 39mm, 40mm, 42mm, 43mm, 45mm, 46.5mm, 48mm, 50mm, 52mm, 53mm, 56mm, 58mm, 60mm, 63mm, 65mm, 70mm, 73mm, 75mm, 78mm, 80mm
Bright Sizes : 22 mm to 60 mm
Industrial Applications & Use Cases
Primary Industries Served
1) Automotive Manufacturing
- Crankshaft/Camshaft blanks
- Connecting rods
- Axle shafts
- Steering components
2) General Engineering
- Heavy-duty bolts & studs
- Gear blanks: spur, helical, bevel
- Spindles & shafts: transmission & machine tools
- Hydraulic cylinder rods
3) Industrial Machinery
- Roller shafts: paper, steel, textile
- Pump shafts: centrifugal & PD pumps
- Compressor parts: piston rods & crossheads
- Material handling: conveyor rollers & pulleys
4) Construction & Infrastructure
- Anchor & foundation bolts
- Tie rods for bridges/buildings
- Crane components: hook blocks & sheave pins
Processing Capabilities & Heat Treatment
Normalizing
- Temperature: 840 ± 20 °C; Cooling: air
- Result: refined grain, balanced properties, good machinability
Hardening & Tempering (Q&T)
- Austenitize: 830–860 °C; Quench: oil (polymer by agreement)
- Temper for target properties:
- 350–450 °C → ~28–35 HRC (≈ 280–340 BHN)
- 550–650 °C → ~220–260 BHN (higher toughness)
Surface Hardening (preferred over carburizing)
- Flame/Induction hardening: typical surface 50–55 HRC with tough core
- Carburizing: not recommended for ~0.40% C steels like EN8/EN8D; choose case-hardening grades (e.g., 20MnCr5/16MnCr5/8620) for 58–62 HRC deep cases
Machinability
EN8D offers good machinability (≈ 70% relative to free-cutting mild steel = 100%). Excellent for turning, good for milling/drilling, suitable for thread cutting, and compatible with CNC machining centres.
Quality Standards & Certifications
Standards & Cross-References
- India: IS 7283
- British (legacy): BS 970 080M40 (reference)
- Europe: EN 10083-2 C40 (quenched & tempered steels)
- USA: AISI/SAE 1040
- Germany (legacy): DIN 17200 Ck40 (reference)
Quality Assurance Measures
- Chemical Analysis: spectrometer testing heat-wise
- Mechanical Testing: UTM for tensile properties (IS 1608 / ASTM E8); hardness to IS 1500 / ASTM E10
- Ultrasonic Testing: per EN 10308 (class by agreement; routine on ≥ 40 mm)
- Dimensional Inspection: calibrated measurement (laser/GA as applicable)
- Surface Quality: visual and magnetic particle inspection
- Mill Test Certificate: EN 10204 Type 3.1
Selection Guide: Choosing the Right EN8D Round Bar
Step 1: Add Machining Allowance
- 23.5–40 mm: +2–3 mm
- 40–60 mm: +3–4 mm
- 60–80 mm: +4–5 mm
Step 2: Optimise for Cost
- Balance between standard stock sizes and machining time
- Use quantity breaks for bulk orders
Advantages of EN8D vs Alternatives
Compared to Mild Steel (EN3/EN1A)
- Higher strength allows smaller, lighter components.
- Better surface hardenability (flame/induction)
- Improved fatigue performance (depends on finish & geometry)
Compared to Case-Hardening Steels (EN32/8620)
- Lower material & processing costs where a deep hard case is not required
- Better core strength than typical carburising grades
Compared to Alloy Steels (EN24/4140)
- Generally better machinability
- Lower material cost and simpler heat treatment
Storage & Handling
Storage
- Prefer indoor storage; use elevated racks to avoid ground moisture
- Apply light oil for long-term storage (> 3 months)
- Recommended ambient: −10 °C to 40 °C; RH < 65%
Handling
- Avoid impact damage; support long bars at multiple points
- Protect finished surfaces with wrapping
Frequently Asked Questions (FAQ)
Q1: How is EN8 different from EN8D?
EN8D is a higher-quality variant of EN8 with tighter controls on elements such as C and Mn It offers more consistent properties and heat-treatment response, so it’s preferred for critical parts.
Q2: Can EN8D be welded?
Yes, with procedure control. Preheat 150–200 °C for sections > 30 mm, use low-hydrogen electrodes (e.g., E7018), keep interpass ≤ 200 °C, allow slow cooling, and consider PWHT at 600–650 °C for critical applications.
Q3: What surface hardness can I achieve?
With flame/induction hardening, typical surface hardness is ~50–55 HRC with a tough core. For 58–62 HRC deep cases, select a carburising grade such as 20MnCr5/16MnCr5/8620 instead of EN8D.
Q4: How do I calculate bar weight?
Weight (kg/m) = (π × D² × 7.85) / 4000 where D = diameter in mm Example: D = 50 mm → Weight ≈ 15.41 kg/m
Q5: What about fatigue performance?
EN8D shows good fatigue resistance; the endurance limit for polished, normalized specimens is typically ~350–400 MPa. Fatigue life can improve with Q&T, surface finish, and proper filleting. Always validate on the actual component.
Q6: What certificates are supplied?
Standard supply includes MTC to EN 10204 Type 3.1, chemical analysis, and mechanical test reports. UT per EN 10308 by agreement (standard on ≥ 40 mm; smaller sizes on request). MPI/other NDT available as required.
Ordering Information & Technical Support
Why Choose Ambhe Ferro Metal Processors Private Limited?
- Extensive Inventory: 23.5–80 mm diameters
- Quality Assurance: Can provide BIS certified material with full Traceability. Also we can provide EN 10204 Type 3.1 certification
- Technical Expertise: Guidance on grade selection, and tolerances
- Competitive Pricing: Direct mill relationships
- Flexible Delivery: Pan-Maharashtra logistics
For quotations, datasheets, or samples, contact Ambhe Ferro Metal Processors Private Limited. We can also develop custom sizes to your specifications.
We supply En8d to various national and international markets. In India, we supply En8d steel to a number of companies/industries in Mumbai (eg Vasai Virar, Mira Bhayendar, Navi Mumbai), Pune (eg. Pimpri Chinchwad, Chakan, Bhosari, Ranjangaon, etc), Aurangabad (eg. Waluj, Chikalthana, etc.), Nashik (eg. Ambad, Satpur, Sinnar, etc.), Ahmednagar, Rajkot, Ahmedabad, Thane, Umergaon, Ambernath, Rabale, Nagpur, Kolhapur, Sangli, Belgaum, Bangalore, Goa, Chennai, Dubai, etc.
