(1) rolled H-beam steel is commonly used in domestic and foreign high-rise steel buildings, for beams, columns, braces and other components can be applied. H-beam has the following advantages: 1), very useful to improve the bearing flange width around the weak axis direction. 2), upper and lower edges parallel flange plates for easy connection structure. 3) higher than the H-beam welding quality, the price is low. (2) H-beam Category: Rolled H-beam steel for structural steel Q235 carbon steel, low alloy steel Q345 and Q390 steel, and specify its quality level. 1) wide flange (HW): This series can be used as columns and beams, its flange wide cross-section aspect ratio of 1: 1. Weak axis radius of gyration relatively large load capacities for good. Sectional specification: 150x100 ~ 600x300mm. 2) in the flange (HM): This series can be used as columns and beams, its flange width than the width of flange (HW) narrower sectional aspect ratio of 1: 1.3 to 1: 2, sectional specification: 150x100 ~ 600x300mm. 3) narrow flange (HN): This series is often used as beams, its narrow flange, also known as H-shaped steel beam type, cross-sectional aspect ratio of 1: 2 to 1: 3, with good flexural capacity, section height 100 ~ 900mm. 4) with H-shaped steel pile (HP): This series is often used as steel piles, the aspect ratio of 1: 1, the cross-section specifications: 200x200 ~ 500x500mm, and most of these H-beam flange thickness with the web. (3) Q235 and Q345 steel quality levels and ensure that the project 1, quality grade quality steel grade Q235 Q235 steel and ensure that the project is divided into A, B, C, D four, the minimum quality requirements for a Class A, to D grade highest. 1) Q235A grade steel to ensure project A, mechanical properties ensure that the project: have a yield point, tensile strength, and elongation B, the chemical composition to ensure that the project: carbon, manganese, silicon, sulfur, phosphorus five, but three When qualified mechanical properties, carbon, manganese content may not be as delivery conditions, but it should indicate their content quality specification. 2) Q235B, C, D grade steel ensure that the project A, mechanical properties ensure that the project: the yield point, tensile strength, elongation, V-notch impact toughness, cold performance of five, including the impact test temperature toughness, for B, C, D grade steel respectively 20 ℃, 0 ℃ and -20 ℃, D grade test temperature test case of negative temperature; B, the chemical composition to ensure the project: carbon, manganese, silicon, sulfur, phosphorus five, and content of residual elements should also be eligible. Five assurance projects, mainly in the sulfur and phosphorus content level of distinction B, C, D grade steel, D level was the lowest. In addition, to ensure that all Eligible five, carbon and manganese content lower limit may as delivery conditions.