Project Description
AISI 4135 Steel Bar – Premium Cr-Mo Alloy for Oilfield & Mining
AISI 4135 is a premium chromium-molybdenum alloy steel renowned for its excellent toughness, high tensile strength, and superior hardenability. ShunFu Metal specializes in manufacturing and supplying this high-performance 4135 steel bar specifically for the demanding oil & gas and mining sectors.
As an API Q1 and ISO 9001 certified manufacturer and a trusted supplier to the world's top 10 oilfield service companies, we possess the technical authority and equipment to produce this grade with strict metallurgical control.
Backed by our extensive export experience to over 52 countries, we ensure you receive reliable materials tailored to your exact operational requirements.
Equivalent Grades
| US / ASTM | UNS | Germany / DIN | China / GB | Japan / JIS |
|---|---|---|---|---|
| AISI 4135 | G41350 | 1.7220 / 34CrMo4 | 35CrMo | SCM435 |
Key Applications
- Drill Collar Blanks (Oil & Gas): Supplied as precision-machined hollow bars or heavy-wall tubes, utilizing ShunFu Metal's BTA deep hole boring and long-distance gunhole-drilling capabilities to guarantee perfect concentricity and wall thickness uniformity. Explore our precision-machined drill collar blanks for downhole drilling assemblies.
- Valve Body Forgings (Oil & Gas): Delivered as customized forged round bars, fully heat-treated in our API-calibrated furnaces to ensure uniform fine sorbite structures capable of withstanding high-pressure fluid control environments.
- Rock Drill Steel Components (Mining): Provided as peeled or turned 4135 steel bar, precision-machined using our in-house CNC lathes and milling centers to endure severe impact and fatigue in underground mining operations.
- Pup Joints and Tool Joints (Drilling): Supplied as quenched and tempered solid bars or pre-drilled hollow bars, engineered by our metallurgy team to achieve maximum yield strength and exceptional resistance to SSCC. See our range of heavy-weight drill pipe and tool joint materials for demanding drilling operations.
Specifications & Standards
ShunFu Metal strictly organizes the production of 4135 steel bar according to the following international standards, and our fully equipped metallurgical laboratory can issue corresponding material test certificates tailored to your specific project requirements.
- ASTM A29 / A29M : Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought
- ASTM A322 : Standard Specification for Steel Bars, Alloy, Standard Grades
- EN 10083-3 : Steels for quenching and tempering — Part 3: Technical delivery conditions for alloy steels (as 34CrMo4)
- GB/T 3077: Alloy Structure Steels (as 35CrMo)
- JIS G4053 : Low-alloyed steels for machine structural use (as SCM435)
Available Sizes & Delivery
ShunFu Metal offers highly flexible supply options for 4135 steel bar. We supply hot-rolled round bars (Φ20mm – Φ150mm), forged round bars (Φ150mm – Φ800mm) featuring a high forging ratio for superior internal grain structure, and precision hollow bar solutions. Our facility is fully equipped with API-calibrated heat treatment furnaces and advanced machining tools, including BTA boring and long-distance gunhole drilling.
Delivery & Minimum Order Quantity (MOQ)
- Ready Stock: Common sizes are available from our 8,000-ton warehouse inventory, allowing for single-piece orders with a rapid 7-day delivery.
- Custom Forged/Rolled: Typically requires a 3-ton MOQ with a 30-day lead time.
- Small Batch Special Melts: Our small induction furnaces allow custom melting starting from just 3–5 tons.
- Large Volume Orders: Processed via our 30–60 ton EAF for rapid, bulk delivery.
Chemical Composition
At ShunFu Metal, we verify the chemical composition of every single heat using in-house spectrometry before pouring. This ensures that the elemental makeup of your 4135 steel bar strictly complies with specification requirements, and our team of 22 metallurgy engineers can even fine-tune the composition to meet your specific mechanical demands.
| Element | AISI 4135 (ASTM A29) | 34CrMo4 (EN 10083-3) |
|---|---|---|
| Carbon (C) | 0.33 – 0.38% | 0.30 – 0.37% |
| Manganese (Mn) | 0.70 – 0.90% | 0.60 – 0.90% |
| Silicon (Si) | 0.15 – 0.30% | ≤ 0.40% |
| Chromium (Cr) | 0.80 – 1.10% | 0.90 – 1.20% |
| Molybdenum (Mo) | 0.15 – 0.25% | 0.15 – 0.30% |
| Phosphorus (P) | ≤ 0.035% | ≤ 0.025% |
| Sulfur (S) | ≤ 0.040% | ≤ 0.035% |
Melting & Processing
ShunFu Metal offers flexible melting routes for 4135 steel bar. Our standard process is EAF + LF + VD for excellent purity.
For stricter requirements — such as sour service drill stem components — we provide ESR or PESR, which deliver superior cleanliness and microstructural homogeneity. Customers can consult our engineering team to select the optimal melting solution for their specific oilfield application.
Mechanical Properties
ShunFu Metal guarantees these mechanical properties by issuing comprehensive test reports from our fully equipped, accredited metallurgical laboratory prior to delivery. All test data for your 4135 steel bar is 100% traceable to the specific heat and batch number.
| Condition | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Reduction of Area (%) | Hardness (HB) |
|---|---|---|---|---|---|
| Quenched & Tempered | ≥ 980 | ≥ 785 | ≥ 12 | ≥ 45 | 269 – 341 |
| Normalized | ≥ 740 | ≥ 460 | ≥ 15 | - | ~ 229 |
| Annealed | - | - | - | - | ≤ 212 |
Heat Treatment
ShunFu Metal's heat treatment facility utilizes API-calibrated furnaces that undergo rigorous regular auditing. This guarantees exceptional temperature uniformity and process repeatability, ensuring that every 4135 steel bar achieves a fully tempered martensite or fine sorbite structure, which is highly desirable for resistance to sulfide stress corrosion cracking in oilfield environments.
| Process | Temperature Range (°C) | Cooling Method |
|---|---|---|
| Normalizing | 860 – 900 | Air cooling |
| Annealing | 800 – 850 | Furnace cooling |
| Quenching | 840 – 880 | Oil or Water quenching |
| Tempering | 540 – 680 | Air or Water cooling |
Surface Finish & Machining
Leveraging our 45 advanced cutting machines, ShunFu Metal provides exceptional surface finish and precision machining for 4135 steel bar. Depending on your product, we offer turning and milling (Ra 3.2–6.3 µm) or precision grinding (Ra 0.8–1.6 µm) with tight dimensional tolerances (h9–h11).
For hollow bars and drill collars, our factory-direct capabilities include BTA deep hole boring, CNC finishing, roller burnishing, and shot peening to enhance fatigue life. By integrating these processes in-house, we eliminate third-party delays and guarantee your machined components arrive ready for immediate downstream manufacturing.
Quality Assurance & Inspection
ShunFu Metal enforces rigorous quality control throughout the production of 4135 steel bar. Our inspection protocol includes UT, chemical analysis, mechanical testing, dimensional checks, four-quadrant hardness testing, and detailed metallographic examination.
As an API Q1 and ISO 9001 certified manufacturer, our quality management ensures uncompromising material integrity for critical oil and gas applications. We provide EN 10204 3.1 certification as standard, with 3.2 certification available upon request. We also welcome third-party inspections from agencies like SGS or TÜV to further validate our zero-defect delivery.
Packing & Shipping
With experience exporting to over 52 countries, ShunFu Metal ensures secure shipping for every order. Black-surface 4135 steel bars are tightly bundled with steel wire. Bright or precision-machined products receive a heavy anti-rust oil coating and multi-layer protective wrapping to preserve surface roughness and dimensional accuracy throughout global ocean transit.
Frequently Asked Questions
Can ShunFu Metal supply AISI 4135 steel bar to API and ASTM specifications?
Yes. Backed by our API Q1 certification and a dedicated team of 22 metallurgy engineers, ShunFu Metal strictly produces 4135 steel bar in full compliance with ASTM A29, ASTM A322, and relevant API standards, ensuring optimal performance and safety for critical oilfield tools such as drill collars and valve bodies.
What is the minimum order quantity for 4135 steel bar?
For standard sizes available in our 8,000-ton ready stock, we accept orders starting from just 1 piece with a rapid 7-day delivery. For custom forgings or special melts, the MOQ is typically 3 tons with a 30-day lead time, supported by our flexible induction and EAF melting routes.
Does ShunFu Metal provide deep-hole drilling and machining for 4135 steel bar?
Absolutely. We are equipped with state-of-the-art BTA boring and long-distance gunhole-drilling machines. This allows us to convert solid 4135 steel bar into precision hollow bars or drill collar blanks directly in our facility, saving significant secondary machining time and costs.
How does ShunFu Metal ensure material traceability for 4135 steel bar orders?
We verify the chemical composition of every single heat using in-house spectrometry before pouring. All mechanical test data is 100% traceable to the specific heat and batch number. We provide EN 10204 3.1 certification as standard, with 3.2 certification and third-party inspections from SGS or TÜV available upon request.
What melting processes are available for custom 4135 steel bar orders?
ShunFu Metal offers flexible melting routes. Our standard process is EAF + LF + VD for excellent purity. For applications requiring superior cleanliness and homogeneity — such as sour service drill stem components — we provide ESR or PESR. Our engineering team can help select the optimal route for your specific oilfield application.
Is AISI 4135 steel bar suitable for sour service and H2S environments?
Yes. When properly quenched and tempered to achieve a fully tempered martensite or fine sorbite microstructure, AISI 4135 steel bar exhibits excellent resistance to sulfide stress corrosion cracking (SSCC). ShunFu Metal's API-calibrated heat treatment furnaces ensure uniform mechanical properties throughout the cross-section, making our 4135 bars highly suitable for NACE MR0175/ISO 15156 compliant oilfield equipment.