Hainan Steel Wholesale
Medium thick plate refers to steel plates with a thickness of 4.5-250mm, including ordinary carbon plate, high-quality carbon plate, low alloy plate, ship plate, bridge plate, boiler plate, container plate, etc. Thick plates with a thickness of 25.0-100.0mm are called thick plates, while those with a thickness exceeding 100.0mm are called extra thick plates.
Classification of medium and thick plates
Medium thick plates are classified not only by size, but also by strength, chemical composition, purpose, and delivery status. According to strength classification, the lower limit of tensile strength is generally used for classification. High strength steel plates with a tensile strength of 50kgf/cm or more are called high-strength steel plates. According to chemical composition, it is divided into ordinary steel plates and special steel plates, the latter including stainless steel plates and composite steel plates. According to their uses, they can be roughly divided into shipbuilding steel plates, welded structural steel plates, boiler and pressure vessel steel plates, low-temperature steel plates, corrosion-resistant steel plates, welded pipe steel plates, and special purpose steel plates. According to the delivery status, there are three types of steel plates:rolled steel plates, heat treated steel plates, and shot blasted and coated steel plates. Due to the needs of large structures and shipbuilding, the production of shot blasted and coated steel plates has been increasing year by year.
Medium thick plate material
The raw materials used in the medium and heavy plate rolling mill include blooming slab, continuous casting slab, steel ingot, and forged billet. The maximum width=100% of the initial rolling billet is 2300mm, the maximum thickness is 610mm, and the maximum weight is 45 tons. The development of continuous steel casting technology has not only increased the yield of medium and thick plate workshops, reduced production costs, but also improved the quality of steel plates. Therefore, the proportion of continuous casting billets used in medium and thick plate rolling mills is constantly increasing, with some reaching 100%. With the adoption of new processes, the yield rate of medium and thick plate mills from slab to finished steel plate has reached 94.2%. If there are no blooming and continuous casting slabs, flat steel ingots can be used as raw materials. Forged blanks are only used as raw materials in the production of special medium and thick plates.
The production process of medium and thick plates
The production process of medium and thick plates is usually coordinated with controlled rolling and adopts a low-temperature furnace heating system, which can save fuel consumption. The rolling process is divided into three stages:
1. Forming rolling, eliminating the influence of the surface of the slab and improving the accuracy of width=100% control, carries out 1-4 passes of rolling along the length or diagonal direction of the slab. Roll the billet to the required thickness.
2. Widening rolling is an important process that distinguishes medium and thick plates from other types of plate rolling. To achieve the required width=100% for the rolled product specifications, the slab is rotated 90 ° and rolled along the width=100% direction.
3. Precision rolling, widening rolling, and then turning 90 ° back to the original length direction of the billet, rolling to the thickness of the finished plate. Properly formulating the medium and thick plate rolling process can improve the production capacity of the rolling mill, the quality of the steel plate, and the yield. To ensure the flatness of the steel plate, in addition to taking various measures to ensure the shape of the plate, each steel plate with a thickness of less than 40mm needs to be hot straightened, and uneven cold steel plates need to be cold straightened. For cold shear finished plates, the steel plate should be cooled to below 150, cooled evenly, and the cooling speed should be appropriate; Since the use of rolling shear machines for cutting, the problem of shear bending defects has been basically solved; Adjusting the gap between the cutting edges can greatly improve the quality of the steel plate shear section. According to the quality requirements of the steel plate, ultrasonic testing should be carried out at different depths, and comprehensive testing should be conducted on the four edges of the welded pipe plate. heat
