High-Performance Steel Sheet for CRT Reinforcing Bands Developed
NKK has developed a new high-performance steel sheet, designed for use in reinforcing bands for TV cathode-ray tubes (CRTs), which effectively combines magnetic shielding properties and high strength. The new cold-rolled steel sheet, which is electro-plated with a zinc-nickel alloy and features a high-tensile strength of more than 340MPa, has already been adopted by Sony for use in its WEGA series of large flat-screen TV sets.The new material offers a substantial improvement in picture quality. Because the space inside a CRT is under high vacuum, it is necessary to prevent distortion of the front screen panel, which otherwise tends to be sucked inside and become concave. Therefore,a steel-sheet reinforcing band is shrink-fitted to the edges of the panel, helping to minimize the distortion of the screen and picture, which results from shifting of the point at which the electron beam hits the screen. Larger CRTs are especially vulnerable to magnetic interference, which leads to diverting the electron beam and color distortion. Preventing this has been a major issue for manufacturers. Development of very large TV sets has also made weight reduction a key issue, prompting calls for the development of high-tensile strength steel for reinforcing heat-shrink bands. In response to Sony's requests, NKK undertook to develop a new heat-shrink band material by combining high-tensile strength and magnetic shielding properties. With conventional steels, it has been difficult to satisfy both properties at the same time. NKK succeeded in commercializing a new steel sheet that combines the two desired properties, by optimizing the steel composition and rolling/annealing conditions. The new steel sheet is available in a thickness of 1-1.2mm with a width of 900-1,000mm and is produced at the cold rolling and electro-plating lines of the Fukuyama Works. Current production levels are totaling around 1,000 tons a year, but following shipments to Sony, NKK has begun supplying samples to other customers to promote further demand and hopes to boost annual production to between 5,000 and 10,000 tons. |
