🔧 Weldability of 35CrMo Alloy Steel

✔ Carbon Equivalent (Cₑq) & Weldability:
35CrMo alloy steel has a carbon equivalent of approximately 0.60–0.72%, which means it requires controlled welding procedures to avoid cracking and brittleness. It is not considered a free-machining or easy-to-weld steel, but it is weldable with the correct approach.

✔ Preheat & Interpass Temperature:
A preheat temperature between 300–750°F is recommended depending on part thickness. During multi-pass welding, interpass temperatures should be maintained above 300°F to prevent rapid cooling and cracking in the heat-affected zone.

✔ Recommended Welding Consumables:
Use low-hydrogen electrodes compatible with Cr-Mo steels, such as AWS E8018-B2 or E8018-B3. These filler metals offer good ductility, toughness, and resistance to hydrogen-induced cracking.

✔ Post-Weld Heat Treatment (PWHT):
A stress-relief heat treatment between 1100–1400°F is highly recommended after welding. This process helps reduce residual stress, soften the heat-affected zone (HAZ), and improve long-term performance under impact and fatigue loading.

✔ Additional Welding Best Practices:
Keep all weld surfaces clean and free from rust, oil, and moisture
Use stringer beads instead of weave beads to limit heat input
Clean slag between weld layers in multi-pass welds
Avoid welding in damp or windy conditions to prevent porosity

⚙️ Summary:
35CrMo is a high-strength alloy steel with excellent toughness and fatigue resistance. While it requires careful welding practice, it performs exceptionally well in applications involving shock, rotation, and impact loading.