Japan's steel companies have the production capacity of the general strength level of the ship plate production capacity, but with the ship load of the upgrade, the general strength level of the ship plate has been far from meeting the requirements, therefore, high-strength level ship plate ratio rise. At present, the proportion of Japanese shipbuilding industry using high strength grade ship plate has reached about 70%. In 2006, the Japanese steel companies for the market demand, focus on the expansion of high-level ship plate and other high value-added products, and in the development of high-strength ship plate to play their own technical and technical characteristics, to develop a variety of high-strength marine steel plate.
1, Nippon Steel Corporation hull with ultra-fine grain steel plate "HIAREST"
In order to improve the safety of large ships in accidents such as impact and large-scale earthquakes, Nippon Steel developed new steel grades with good brittleness crack crack performance equivalent to EH36 for hull. The main feature of this steel is in the process of heating the ferrite structure, the ferrite grain superfine. The 25 mm thick steel plate produced by this method has a very fine grain size and an average grain diameter of only 2 microns. In the case of 10% plastic deformation, the steel sheet with such a structure still has good crack-preventing performance in low temperature environment of 40 degrees Celsius, while the traditional EH36-class ship plate is only in the case of plastic deformation, Only with such a performance.
2, JFE company high-strength ship plate
(1) large wire energy welding steel plate
In order to improve the efficiency of shipbuilding, the general use of welding wire energy to increase the method. JFE has developed a new JFE EWEL technology to improve the toughness of HAZ (weld affected area). The core of this technique is to suppress the formation of ferrite in HAZ austenite by microalloying, and to optimize the composition design by ultra-cooling technology (Super-OLAC). On the basis of this technology, JFE has developed a marine yield strength of 390 MPa large container ship plate and 355 MPa low temperature F grade steel plate (mainly for LPG ship), 390 MPa level line energy of 68Kj / mm.