LCB is a grade of low-temperature carbon steel cast steel material in valve manufacturing. It is specially designed for low-temperature working conditions. Its core is to improve the sealing and durability of valves in extremely cold environments18. The following is a detailed description from three aspects: material properties, application scenarios and technical specifications.
1. Material properties
Standards and composition:
LCB is defined according to the American ASTM A352 standard, with a UNS number of J03303, and belongs to the category of low-temperature carbon steel cast steel. Its chemical composition is low carbon (C≤0.30%), manganese (Mn≤1.00%) and silicon (Si≤0.60%), the total amount of impurities is controlled at ≤1%, and the mechanical properties include tensile strength of 450-620MPa and elongation after fracture ≥24%, ensuring that the material is resistant to brittle cracking at low temperatures.
Temperature adaptability:
The applicable temperature range is -46℃ to +343℃ (or -46℃ to +345℃, with slight differences from different sources). The stress is released through deep cryogenic treatment process (such as cooling parts for 2-6 hours) to prevent the risk of leakage caused by low-temperature deformation.
Equivalent material:
Forgings correspond to A350 LF2 grade, and the domestic equivalent material is 16Mn steel, which is used to simplify supply chain adaptation.
2. Application in valves
Core use:
LCB is mainly used to manufacture key components of cryogenic valves, such as valve body and valve cover, and is suitable for cryogenic medium transportation systems such as liquefied natural gas (LNG), liquid ammonia, liquid oxygen, ethylene and propane.
Valve type:
Gate valve and ball valve: such as cryogenic flange gate valve (DZ41H/DZ40Y series), the pressure relief hole design prevents abnormal pressure rise in the middle cavity.
Butterfly valve: As a valve body material, it is suitable for carbon steel butterfly valve structure.
Structural optimization:
Long-neck bonnet design (neck length up to 250mm) is often used to reduce cold conduction and ensure sealing reliability below -100℃; at the same time, the valve diameter covers DN16 to DN600, meeting the needs of small and medium-sized pipelines.
3. Technical limitations and industry specifications
Applicable boundaries:
LCB is not suitable for high temperature (>343℃) or high pressure (exceeding PN16, i.e. 1.6MPa) scenarios. It is easy to cause jamming or sealing failure due to thermal expansion differences at high temperatures.
Industry standards:
Following GB12237-89 (General Specifications for Valves) and ASME B16.34 (Pressure-Temperature Ratings), it is widely used in petrochemical, liquefied natural gas storage and transportation and ship systems.
Alternative solutions:
Lower temperatures (such as -101℃) need to be upgraded to LC3 (5% nickel steel) or CF8 stainless steel, and high temperature environments use alloy steels such as WC6.