MACHINING STRUCTURAL STEEL (GB 8731-88)
Structural steel is a special type of steel used in the construction of buildings and other structures. Structural steel components typically comprise one or more of the following materials: hot-rolled steel, cold-rolled steel, galvanized steel and pre-painted steel. It is important that the steel is properly machined in order to ensure the integrity and safety of the structure.
This article describes the machining of structural steel according to the Chinese National Standard GB 8731-88 for machining of structural steel building components. This standard determines the size, shape and surface finish of structural steel components, as well as the requirements for process control, inspection and testing.
The first step in machining structural steel is to select the appropriate grade of steel. The selection of the grade should be based on the desired properties and strength of the component that is to be constructed. The grade should also be appropriate for the type of machining process that is to be used. For example, when performing turning operations on structural steel, the grade should be selected depending on the severity of the turning operations.
Once the grade has been selected, machining can begin. This includes cutting, turning and milling operations. All machining operations must be performed within specified tolerances for the size and profile of the component. The cutting tool should be made of a material that is suitable for the grade of steel being machined. For example, high speed steel (HSS) is typically used when cutting or turning mild metals or low alloy steels.
When machining structural steel, it is important to pay attention to various process control parameters, such as feed rates and spindle speeds. For example, lower feed rates are typically required when machining structural steel, as the harder material requires less heat build up, which can cause tool wear. The spindle speed should also be kept within specified limits, as different grades of steel require different speeds to be machined.
In addition to process control parameters, appropriate inspection and testing measures should be performed to ensure the quality of the machined component. Visual inspections should be performed at different stages of the machining process to ensure that the component is free of any defects. Ultrasonic, x-ray and dye penetrant testing should also be conducted to ensure that the component meets the required quality standards.
In conclusion, machining structural steel components according to the Chinese National Standard GB 8731-88 is an essential part of building construction. The steel components must be properly machined to ensure the safety and integrity of the structure. The selection of the grade, as well as process control parameters and inspection and testing measures should all be taken into consideration when machining structural steel.
