High Strength Low Alloy Steel Plate

Regular quality steel plate
It is mainly the ordinary quality of C steel, which is applicable to plates with a maximum C content of 0.33 %. Plates of this quality are not expected to have the same degree of chemical uniformity, internal soundness, or freedom from surface defects which is associated with structural quality, ship building quality, armour quality or pressure vessel quality plate. Regular quality normally has standard composition ranges and is not usually produced to mechanical property requirements. Regular quality is analogous to merchant quality in case of steel bars since there are normally no restrictions on deoxidation, grain size, check analysis, or other metallurgical factors.

Ship building quality steel plate
Several qualities of steels are used for shipbuilding. These are (i) different grades of mild steels, (ii) HSLA steels, (iii) TMCP steels, (iv) normalized rolled steels, (v) high strength steels (HSS), (vi) new anti-corrosion steel plates for crude oil tankers which contribute to higher performance in ships through improved corrosion resistance, (vii) clad steel plates for chemical tankers, and (viii) stainless steels. The steels are to meet various shipbuilding requirements, such as reduction in welding man-hours, shortening of welding lines, elimination of cutting steps, stabilization of fabricated part quality and reduction in control costs.

Pressure vessel steel plate
Steel plates intended for fabrication into pressure vessels are to conform to specifications different from those of similar plate intended for structural applications. The major differences between the two groups of specifications are that pressure vessel plates are to meet requirements for notch toughness and have more stringent limits for allowable surface and edge defects. The specifications requirements for pressure vessel steel plates required to be met are given in various standards. All of the steel plate specifications are furnished according to both chemical composition limits and mechanical properties. Mechanical tests of pressure vessel steel plate involve a minimum of one tensile test for each as-rolled plate or a minimum of two tensile tests for quenched and tempered plates. The mechanical property requirements are given in the various standards.

Armour quality steel plate
Armour steel is basically a HSLA or low alloy structural steel which has been treated to have property of very high resistance to penetration. This property to the steel is normally imparted by the heat treatment usually by the thermo mechanical treatment. It is well known that the resistance to penetration of steel can be improved by increasing its texture intensity which can be obtained by thermo-mechanical treatment. The mass effectiveness of the armour increases with the hardness of the material. However, very hard armour tends to be brittle and to shatter when hit. The main alloying elements of the armour steel are Ni, Cr, and Mo.