Recently, VL4-4MOD low temperature steel for LPG transport ships, developed by the Iron and Steel Research Institute of LNAG Special Steel Technology Group and mass-produced by LNAG Medium and Heavy Plate Division, achieved the world's first launch. The advent of this product marked the breakthrough of LNAG ship plate steel in terms of low temperature resistance, product thickness and strength.
The LPG carrier mainly transports petroleum hydrocarbons with propane and butane as the main components or a mixture of the two, which has very strict requirements on the material performance of the chemical tank. The service temperature is usually around -55℃, and expensive Ni-based steel plates are used. . In 2020, among the design requirements of the 5000 cubic meter LPG carrier built by CIMC, the application of VL4-4MOD products was proposed for the first time to reduce manufacturing costs, and stringent index requirements were put forward in terms of strength, low temperature toughness and service safety. .
Based on years of experience accumulated in the field of marine low-temperature steel, the marine steel project team of the State Key Laboratory of Metallic Materials for Marine Equipment and Their Applications, combined with the LNAG medium and heavy plate business unit, relying on the strategy of LNAG and CIMC The cooperation agreement is to form a project research team with CIMC. Through research and research, special composition design is adopted for the key characteristics of marine VL4-4MOD low temperature steel such as high strength, high toughness, cold crack resistance and easy welding. ，Combined with special rolling technology to obtain excellent performance and realize the stable rolling of VL4-4MOD low temperature high strength thick plate.
It is reported that this product is currently the highest toughness grade steel for C-Mn series of marine steel plates, breaking through the limits in terms of low temperature resistance, product thickness and strength. The maximum thickness of the product is 60mm, the strength of the base material and the post-weld heat treatment is higher than the existing standard by more than 50MPa, and the toughness service evaluation temperature needs to be lowered by 20℃ on the basis of the service temperature, that is -75℃.
Carrying out low-temperature steel research to meet the major needs of steel materials for ships and marine engineering in complex service environments such as low temperatures is one of the major issues that the State Key Laboratory of Metallic Materials for Marine Equipment and Their Applications has been focusing on in recent years. The mass production of low-temperature steel has achieved a breakthrough in the localization of low-temperature steel materials in China.
This time, LNAG completed the VL4-4MOD R&D and classification society certification in a short period of time, becoming the first company in the world to be qualified to produce VL4-4MOD, once again demonstrating LNAG's technological innovation capabilities.
In recent years, LNAG has achieved leapfrog development. Relying on the National Key Laboratory of Metal Materials for Marine Equipment and Its Application, it has completed the challenge of localization of high-end materials. It provides services for China’s nuclear power equipment, ultra-large oil tankers, container ships, luxury cruise ships, drilling platforms, etc. The maritime "Big Mac" provided high-end steel materials and became the trump card "main force" supporting China's nuclear power and marine equipment manufacturing.