Base Metal Preheat Temp. Postheat °F °C Low carbon Steel (up to 40%C) for thin sections only Not Required Not Required Air Cool Low Carbon Steel (up to 40%C) for thick sections only High Carbon Steel (over 40%C) for thin sections only Low Alloy Steels (up to 10% alloy) for thin sections only 200-600 93-315 Slow-Cool High Carbon Steels (over 40%C) for thick sections only Low Alloy Steel (up to 10% alloy) for thick sections only 300-600 148-315 Slow-Cool Air-Quench Steels 1100-1200 593-648 Slow-Cool High Chromium-Nickel (Austenitic) Stainless Steels (304, 309, 316, etc.) thin sections only Not Required Not Required Air-Cool High Chromium-Nickel (Austenitic) Stainless Steels (304, 309, 316, etc.) thick sections only 200-500 93-260 Slow-Cool High Chromium-Nickel (Martensitic) Stainless Steels (410, 416, 420, etc.) thick sections only 400-600 204-315 Maintain at 400°-600° for 4 hrs. per 1 inch thickness, then reduce heat 50° F (10°C) till cool. High Chromium-Nickel (Ferritic) Stainless Steels (430, 442, 446, etc.) thick sections only 200-600 93-315 Maintain at 200°-600° for 4 hrs. per 1 inch thickness, then reduce heat 50° F (10°C) till cool. High Temperature Nickel Alloys (400, 600, 601, 718, etc.) 200-500 93-260 Stress Relieve