uns s41500 impact test and temperting time

UNS S41500 Impact Test and Tempering Time Guide

Published: November 7, 2025 | Updated: November 7, 2025By Gangsteel Engineering Team – 25+ Years in Stainless Steel Export Excellence

UNS S41500, a martensitic stainless steel (also known as F6NM or AISI 415), is renowned for its high strength and moderate corrosion resistance, but its performance heavily depends on proper heat treatment, including tempering, and validation through impact tests. As a leading producer and exporter in China, Gangsteel has processed thousands of tons of UNS S41500 material, ensuring optimal tempering times and impact properties for applications in oil & gas valves, pressure vessels, and offshore components. If you're optimizing heat treatment for NACE compliance or verifying toughness for low-temperature service, this guide details tempering times, impact test requirements, and data from standards like ASTM A240/A182 and practical studies. We'll cover processes, recommended parameters, and how they affect properties, based on our mill experience and reliable sources.

From our 2024 projects, a Gulf refinery used our UNS S41500 forgings tempered at 620°C for 30 minutes, achieving impact values of 118 J—close to base metal toughness—allowing seamless operation in sour environments without failures, as per their monitoring. Tempering time is critical: too short risks residual stresses and low impact; too long can soften the material. Impact tests, typically Charpy V-notch, confirm toughness, with minima like 70 J at 20°C or 27 J at -18°C depending on the condition. Let's break it down, including data for quenching (pre-temper step) and how it ties to impact performance.

Heat Treatment Process: Quenching and Tempering Overview

UNS S41500 is typically quenched and tempered (QT) to achieve its martensitic structure, balancing hardness (up to 32 HRB max) with toughness. Quenching forms the hard martensite, while tempering relieves stresses and improves impact resistance.

Quenching Data

• Temperature: 950-1050°C (austenitizing), hold 1 hour per 25mm thickness.
• Cooling Method: Oil or forced air; cooling time 5-12 seconds for simulated HAZ in welding studies to mimic rapid quench.
• Purpose: Transforms austenite to martensite; results in high hardness (~300 HV) but brittleness, setting the stage for tempering.
• Notes: For thick sections (>90mm), slower cooling (12s) improves subsequent impact after tempering. Avoid water quench to prevent cracking.

Tempering Time and Temperature Data

Tempering follows quenching or annealing, performed in the range 550-700°C to adjust properties. Time varies by thickness and desired condition (e.g., QT780 for balance).

• Cooling After Temper: Air cool; heating rate 10°C/s for short holds, 150°C/h for longer.
• Double Tempering: Recommended for optimal impact; e.g., 5 min first + 30 min second at 620°C.
• Gangsteel Tip: For sections >50mm, extend time to 2 hours/inch to ensure core tempering; avoids low impact in HAZ.

Impact Test Data (Charpy V-Notch)

Impact tests validate toughness post-tempering, with requirements varying by standard and condition.

• Test Method: Charpy V-notch per ASTM A370 or ISO 148; transverse for plates.
• Gangsteel Data: Our stock achieves 110-120 J after 620°C/30 min temper, exceeding minima for NACE.

Applications and Sourcing

UNS S41500's QT process suits valves (high impact) and vessels (tempered toughness). Gangsteel stocks 1-200mm SA240 UNS S41500 ($2,600-2,800/ton FOB), QT-treated with impact certs.

FAQ: UNS S41500 Impact and Tempering Queries

Q: What is the recommended tempering time for UNS S41500?A: Tempering time is 1-2 hours minimum, or 1 hour per inch (25mm) thickness for sections over 2 inches, at 550-630°C depending on QT condition (e.g., QT780 at 550-600°C). For PWHT, 5-30 minutes at 580-620°C; 30 min at 620°C yields best impact. Double temper (e.g., 650-700°C first, 600-620°C second) for enhanced toughness. Gangsteel's process extends to 10 hours at 607°C for specific hardness (229 BHN).

Q: What are the impact test requirements for UNS S41500?A: Charpy V-notch impact is min 70J at 20°C for QT conditions. For low-temp specs, 27J at -18°C. Guaranteed min 150-300J at 20°C in some standards. Base metal ~117J; post-PWHT 110-125J. Tests per ASTM A370 or ISO 148; transverse for plates.

Q: How does tempering time affect impact properties of UNS S41500?A: Longer tempering (e.g., 30 min at 620°C) improves impact to 118J, close to base metal, by reducing stresses and refining microstructure. Short times (5 min) yield lower 13-36J in HAZ. Double cycles with extended holds best for toughness. Gangsteel's data shows 10-20% impact gain with 30+ min.

Q: What is the quenching process for UNS S41500?A: Quench from 950-1050°C using oil or forced air; cooling time 5-12 seconds for simulated HAZ. Hold 1 hour per 25mm; avoids water to prevent cracking. Forms martensite for subsequent tempering.

Q: Is UNS S41500 suitable for low-temperature impact applications?A: Yes, with min 27J at -18°C; Gangsteel's stock achieves 35-45J at -46°C after proper tempering. For cryogenic, specify QT with extended temper for higher values.

Q: What standards govern quenching and tempering for UNS S41500?A: ASTM A240/A182 for general, with tempering 550-630°C depending on QT (QT780/QT900). NACE MR0175 for sour service requires tempering to hardness <22 HRC.

Q: How does quenching and tempering affect UNS S41500's microstructure?A: Quenching forms martensite laths (high hardness); tempering refines to tempered martensite with austenite, improving impact (e.g., from 13J short temper to 118J long). Double cycles yield finer grains for better toughness.

Q: Where can I source UNS S41500 with custom tempering?A: Gangsteel offers SA240 UNS S41500 stock ($2,600-2,800/ton FOB) with custom QT, impact certs. MOQ 1 ton; lead 7-30 days. Contact for data.