Round bar aisi 4140

AISI 4140 is a chromium-molybdenum alloy steel known for its high toughness and fatigue strength. You must verify the chemical composition (Chromium 0.80-1.10%, Molybdenum 0.15-0.25%) and mechanical properties such as tensile strength (typically 850-1000 MPa) and yield strength. Ensure the supplier provides a Mill Test Certificate (MTC) to EN 10204 3.1 standards to guarantee traceability and material integrity.

The delivery condition significantly impacts price and usability. You should specify whether you need the bars in Annealed (softened for machining), Quenched and Tempered (QT) for high-strength applications, or Hot Rolled state. QT (Quenched & Tempered) bars are the most common for industrial components as they offer the best balance of hardness (28-32 HRC typically) and ductility.

For precision machining, request Cold Drawn or Centerless Ground bars which offer tighter tolerances (e.g., h9 or h11). If the material is for heavy forging, Hot Rolled bars with a black surface are more economical. Always confirm the straightness tolerance (usually 1mm/m to 3mm/m) to prevent issues during automated CNC feeding.

When sourcing via Made-in-China.com, you may encounter equivalent grades. The most common matches are DIN 42CrMo4 (1.7225), JIS SCM440, and GB 42CrMo. Ensure the supplier confirms that the specific melt meets the ASTM A29 standard if your project strictly requires the AISI designation.

Steel fraud often involves substituting 4140 with cheaper carbon steel (like 1045). To prevent this, mandate a third-party inspection (SGS or TUV) to perform a PMI (Positive Material Identification) test and a spectrochemical analysis before the balance payment is made. Never rely solely on digital copies of certificates.

Steel prices fluctuate based on raw material costs (iron ore, molybdenum). Negotiate based on theoretical weight vs. actual weight to avoid overpaying. For large orders, try to lock in a fixed price for a 30-day window and request volume-based discounts (typically 5-10% for orders exceeding 20 tons).

To prevent rust during sea freight, bars must be oiled/slushed and wrapped in corrosion-inhibitor (VCI) paper or plastic film. For LCL (Less than Container Load) shipments, ensure the bars are packed in wooden crates or steel-strapped bundles with lifting eyes to prevent bending or surface scratching during port handling.

Utilize Secured Trading Services provided by Made-in-China.com to ensure your funds are protected until the shipping documents are verified. Always verify the supplier's Business License and Export Qualification to ensure they are a legitimate manufacturer or a reputable Tier-1 agent rather than a small trading shell.