telephone：0898—68660833
0898—68623308
telephone：0898—68660833
0898—68623308
1. Categories of construction steel
(1) The general length of threaded steel is 9m and 12m. The 9m long thread is mainly used for road construction, while the 12m long thread is mainly used for bridge construction. The specification range of threads is generally between 6-50mm, and deviations are allowed by the country. There are three types of rebar based on strength:HRB335, HRB400, and HRB500.
(2) Round steel is a solid strip of steel with a circular cross-section, divided into three types:hot rolled, forged, and cold drawn. The specifications of hot-rolled round steel are 5.5-250mm, and small round steel with 5.5-25mm is used for reinforcement, bolts, and various mechanical parts; Round steel larger than 25mm is mainly used for manufacturing mechanical parts or as seamless steel pipe blanks.
(3) There are only two types of wire rods for construction steel, Q215 and Q235. The commonly used specifications include 6.5mm diameter, 8.0mm diameter, and 10mm diameter. Currently, the largest wire rod in China can reach a diameter of 30mm. In addition to being used as reinforcement for building reinforced concrete, wire rods can also be used for wire drawing and mesh. (4) A screw is a threaded steel that is coiled together like a wire. Compared to threaded steel, the advantage of a screw is that the threaded steel is only 9-12 in size, and the screw can be cut freely according to usage needs. Used for hoop reinforcement, distribution reinforcement of slabs, stirrups, wall ties, etc.
2. Specification of profile steel
Steel structural components are generally recommended to directly use steel profiles, which can reduce manufacturing workload and lower costs. When the size of the steel section is not suitable or the component is large, steel plates are used to make it. There are two types of steel profiles:hot rolled and cold formed.
(1) Hot rolled steel plate
Hot rolled steel plates are classified by thickness:(a) thin plates, with a thickness not exceeding 3mm (excluding electrical steel plates); (b) medium plates, with a thickness of 4-20mm; (c) thick plates, with a thickness of 20-60mm; (d) extra thick plates, with a thickness greater than 60mm.
In the drawing, the steel plate is represented by adding a steel plate cross-section before ' - thickness x width=100% x length (in millimeters) ' , such as -12 x 800 x 2100, etc. Generally, steel plates are delivered using standard size flat plates, such as 2m * 6m and other specifications;
(2) Hot rolled section steel
Angle steel - there are two types:equal and unequal sides. Equal angle steel, expressed in terms of edge width=100% and thickness, for example, L100 x 10 is an equal angle steel with a limb width=100% of 100mm and a thickness of 10mm. Unequal angle steel is represented by the width=100% and thickness of both sides, such as L100 x 80 x 10.
Channel steel - There are two size series of channel steel in China, namely hot-rolled ordinary channel steel and hot-rolled light channel steel. The former is represented as [30a], which refers to the type where the outer height=100% of the channel steel is 750px and the thickness of the web plate is the thinnest; The representation of the latter, for example [25Q], represents an outer contour height=100% of 625px, where Q is the pinyin prefix of ' light ' in Chinese. When the same number is used, lightweight ones have a small cross-sectional area but a large turning radius due to their thin web and wide flange, which can save steel and reduce self weight. However, there are relatively few actual products in the lightweight series.
I-beam - similar to channel steel, it is also divided into the two size series mentioned above:ordinary and lightweight. Like channel steel, the centimeter of the outer contour height=100% of I-beam is the model. For ordinary types, when the model is larger, the thickness of the web plate can be divided into three types:a, b, and c. Lightweight ones are no longer classified by thickness due to their thinner wall thickness. There are two ways to represent I-beams, such as I32c, I32Q, etc.
(3) Cold formed thin-walled steel
It is formed by cold bending or molding of 0.42-6mm thick thin steel plates (as shown in the diagram). Pressed steel plate is a thin-walled profile that has been used in recent years, with a thickness of 0.4-2mm. It is used for lightweight roofing and other components.
3. Selection of Steel
The purpose of selecting steel is to achieve structural safety and reliability, while using economically reasonable materials. Therefore, when selecting steel, the following factors should be considered:
(1) The importance of structures or components;
(2) Load nature (static or dynamic load);
(3) Connection method (welding, riveting, or bolt connection);
(4) Working conditions (temperature and corrosive media).
For important structures, structures that directly bear dynamic loads, structures under low temperature conditions, and welded structures, high-quality steel should be selected.
In the guarantee project of Q235A steel, carbon content, cold bending test qualification, and impact toughness value are not necessary guarantee conditions, so they are only suitable for structures that do not directly bear dynamic effects. When used for welding structures, the quality certificate should indicate that the carbon content does not exceed 0.2%.
When selecting Q235A and B grade steel, it is also necessary to select the deoxidation method of the steel.
The steel used for connection, such as welding rods, automatic or semi-automatic welding wires, and bolts, should be suitable for the strength of the main metal.
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