EN 10305-1 42CrMo4 Precision Seamless Steel Tube Cold Drawn Steel Tube BK Condition

EN 10305-1 is the European standard for seamless cold-drawn precision steel tubes. It specifies technical delivery conditions for tubes used in applications requiring close dimensional tolerances, smooth surface finish, and consistent mechanical properties.

The standard covers tubes manufactured from various steel grades, with 42CrMo4 being the most popular choice for high-strength, high-pressure components.

42CrMo4 (also known as 1.7225 or AISI 4140) is a chromium-molybdenum alloy steel known for:

• High tensile strength
• Excellent toughness
• Good fatigue resistance
• Superior hardenability

When supplied under EN 10305-1, 42CrMo4 tubes are delivered in the cold-drawn and stress-relieved (BK) condition – ready for precision machining and demanding applications.

The manufacturing process for EN 10305-1 42CrMo4 precision tubes follows strict quality controls to ensure consistency and reliability.

Step 1 – Mother Tube Production

A solid, round billet of 42CrMo4 steel is heated and pierced to create a hollow seamless shell – the "mother tube."

Step 2 – Pickling & Phosphating

The mother tube is chemically treated to remove scale and apply a lubricant coating. This prepares the surface for cold drawing.

Step 3 – Cold Drawing

The tube is pulled through a die and over a mandrel to achieve precise dimensions. Multiple drawing passes may be used. Cold drawing improves dimensional accuracy, increases strength through work hardening, and produces a smooth surface finish.

Step 4 – Stress Relieving (BK Condition)

After cold drawing, the tube is heat-treated at a controlled temperature (typically 450–600°C) to remove residual stresses from drawing while maintaining improved mechanical properties. Unlike full annealing, stress relieving avoids complete softening.

Under EN 10305-1, tubes can be supplied in several delivery conditions. For 42CrMo4, BK is the most common.

BK condition provides:

• Dimensional accuracy to ISO 8448 (or better)
• Surface roughness typically ≤ 0.8 µm Ra
• Residual stresses reduced by 80–90%
• Good machinability without full softening

EN 10305-1 references the material specifications from EN 10297-1 for 42CrMo4. The chemical composition is tightly controlled to ensure consistent hardenability and mechanical properties.

Note: EN 10305-1 does not specify a free-cutting version. For precision tubes, sulfur is kept low to ensure clean material suitable for non-destructive testing and high-pressure service.

Why 42CrMo4? The combination of chromium and molybdenum gives this grade superior hardenability and strength compared to plain carbon or simple chromium steels.

The mechanical properties of EN 10305-1 42CrMo4 tubes depend on the delivery condition (BK) and the wall thickness. Below are the minimum guaranteed values per the standard.

*Values are minimum requirements per EN 10305-1. Actual values can be higher depending on cold drawing reduction and stress relieving parameters.*

Important: The BK condition is designed for machinability, not final service strength. After machining the tube into a cylinder barrel or component, most customers perform a final quench and temper heat treatment to achieve the full strength potential of 42CrMo4.

Actual tolerances vary by diameter and wall thickness. Please consult our technical team for your specific size requirements.

Primary Use: Hydraulic cylinder barrels

Other Applications:

• Mechanical engineering components
• Heavy-duty vehicle parts
• Oil & gas equipment
• General high-strength mechanical parts

Quick Pick:

We take quality seriously. Every EN 10305-1 42CrMo4 tube we supply is backed by comprehensive testing and traceability.

We supply all tubes with:

• EN 10204 Type 3.1 – Mill test certificate (chemical and mechanical results)
• EN 10204 Type 3.2 – Available upon request (third-party verified)
• Full traceability – Heat number stamped on each tube

EN 10305-1 requires that tubes be free of laminations, cracks, scale (rust), and significant surface defects. For hydraulic cylinder applications, we pay special attention to ID surface finish – typically achieving Ra ≤ 0.8 µm to ensure long seal life.

Ready to order or have technical questions? Our team is here to help.

Please provide the following information for a fast and accurate quote:

• Quantity (pieces or meters)
• Dimensions (OD × wall thickness × length)
• Grade (42CrMo4)
• Standard (EN 10305-1)
• Delivery condition (BK – standard)
• Certification required (3.1 or 3.2)
• Delivery location