Chrome Moly DIN 1.7225 Alloy Steel Bars

Product Description

W.Nr. 1.7225 (standardized as 42CrMo4 under EN 10083-3) is arguably the most widely used Chromium-Molybdenum alloy structural steel in European engineering. When specified in bar stock—whether hot-rolled, forged, or bright-drawn—it serves as the absolute benchmark for high fatigue strength, toughness, and torsional wear resistance.

It is the direct European equivalent to the ubiquitous AISI 4140, but with slightly tighter parameter windows for manganese, sulfur, and phosphorus to ensure higher material cleanliness and more predictable heat treatment response.

1. Chemical Formula (EN 10083-3 / DIN 1.7225)

The balance of chromium and molybdenum gives 1.7225 bars its characteristic hardenability and thermal stability:

2. The Dimension vs. Strength Rule (+QT Condition)

When purchasing 1.7225 bars in the standard Quenched & Tempered (+QT) condition, it is critical to realize that its mechanical performance transitions depending on the cross-sectional size ($d$). Because it doesn't contain nickel (unlike 1.6565), its through-hardening depth shows a distinct profile across larger bars:

3. Alternative Supply States

Depending on the machining plan, 1.7225 bars are distributed in several key structural delivery conditions:

• Soft Annealed (+A): Heat treated to drop hardness below 241 HBW. This is the standard state if you are doing extensive material removal (long drill passes, complex spline hobbing, deep milling) to save tooling cost.

• Treated to Improve Shearability (+S): Softened slightly up to a max of 255 HBW to allow industrial cold-shearing or cold-heading without causing structural cracks.

• Pre-Hardened (+QT): Pre-treated to approximately 28 to 34 HRC. It allows component creation via direct machining, bypassing final quenching lines and avoiding dimensional warping.

4. Technical Processing Realities

• Surface Modification: 1.7225 responds beautifully to surface treatment. While its core remains tough at $\sim30\text{ HRC}$, its skin can be induction-hardened or nitrided up to 50–55 HRC to act as a high-wear bearing surface for pins, journals, or gear teeth.

• Welding Limitations: Due to high crack sensitivity under quick thermal cooling, 1.7225 is classified as poorly weldable. For repair or assembly work, you must preheat the block to $200^\circ\text{C} - 300^\circ\text{C}$ and perform immediate Post-Weld Heat Treatment (PWHT) to temper the newly formed brittle martensite zone.

5. International Equivalents

When reviewing or replacing 1.7225 stock from varying regional sources:

• USA: AISI 4140 / SAE 4140

• Japan: JIS SCM440 / SCM440H

• France (AFNOR): 42CD4

• United Kingdom: BS 708M40 (Classic EN19)

• China: GB 42CrMo / 42CrMoA

• Russia: GOST 38KhM (38ХМ) or 42KhM (42ХМ)