ASTM A387 Grade 5 Class 1 is a high-performance chromium-molybdenum alloy steel plate characterized by excellent high-temperature performance, hydrogen corrosion resistance, and weldability. It serves as a critical material for high-temperature pressure vessels in demanding applications within industries such as petrochemical and power generation.

Key Features and Advantages

1. Excellent high-temperature strength: It has strong resistance to creep and stress rupture at high temperatures.

2. Good resistance to hydrogen corrosion: Chromium can form a stable oxide layer, effectively resisting hydrogen attack in high-temperature hydrogen environments.

3. Moderate oxidation resistance: Its oxidation resistance lies between that of carbon steel and stainless steel.

4. Post-weld heat treatment required: Proper post-weld heat treatment must be performed to ensure the performance of welded joints and relieve stress.

This material is specifically used for manufacturing equipment that operates in high-temperature, high-pressure, and corrosive environments, particularly in the petrochemical and coal chemical industries:

1. Petrochemical industry: Reactors, heat exchangers, and hydrocracking units, which perform excellently in hydrogen environments at 350–480°C.

2. Power industry: Boiler drums and steam pipelines, resistant to high-temperature oxidation and creep.

3. Coal chemical industry: Coal gasifiers and synthesis towers, resistant to corrosive media such as hydrogen sulfide.

4. Nuclear energy sector: Certain nuclear pressure vessel components, which must meet stringent quality control and non-destructive testing requirements.

Welding Precautions

1. Preheating: Preheating must be performed, typically in the range of 150-200°C (300-400°F), to prevent cold cracks.

2. Welding Materials: Low-hydrogen electrodes such as AWS A5.5 E/S 8018-B2 or E/S 8015-B2 are commonly used.

3. Post-Weld Heat Treatment (PWHT): Mandatory requirement. PWHT is typically conducted at 650-700°C (1200-1300°F), with the holding time determined based on thickness.