The Production Process Of Steel Structure

(1) Mechanical indicators of steel: The mechanical indicators of structural steel include yield point, tensile strength, elongation, and low-temperature impact toughness. These indicators should meet the requirements of the "Code for Design of Steel Structures", and the low-temperature impact toughness should be tested only when the structure may work in a low-temperature environment.

(2) Chemical composition of steel: related to the machinability, toughness, and durability of steel. Mainly, the content of carbon, the content of alloying elements, and the limited content of impurity elements such as sulfur and phosphorus should meet the requirements of the specification (GB222-84).

(3) Process performance: Process performance mainly includes weldability and processability. Weldability is related to carbon content or carbon equivalent (low alloy steel), which can be identified by the weldability test. The machinability of steel structure is determined by cold bending tests.

(4) Geometric dimension deviation: The deviation between the external dimensions and theoretical dimensions of steel materials (steel plates, section steel, round steel, steel pipes) must be within the allowable range.

(5) Defects in steel appearance: There must be no air bubbles, scars, cracks, folds, inclusions, or pressed oxide scales on the steel surface, and these defects must be removed. After removal, the depth of the depression at this place should not be greater than the negative deviation value of the steel thickness. In addition, when there is corrosion, pitting, or scratches on the steel surface, its depth should not be greater than 1/2 of the negative deviation value of the steel thickness.

(6) Mechanical cutting of steel structure: Cutting with mechanical force (shearing, sawing, grinding). The corresponding machines include shearing machines, sawing machines, grinding machines, etc., which are more suitable for wire cutting of steel plates or profiles with a thickness of 12-16mm or less.

(7) Gas cutting: use the oxygen-acetylene flame, propane flame, or liquefied petroleum gas flame to melt metal, and blow away the molten metal with compressed air to cut the metal, suitable for curve cutting and multi-head cutting).

(8) Plasma cutting: cutting with plasma arc current, suitable for cutting high melting point materials such as stainless steel.

(9) Thermoforming processing: refers to heating the steel to a certain temperature before processing. This method is suitable for forming, bending, and correcting workpieces that cannot be done at room temperature. The hot end temperature shall not be lower than 700°C. When the heating temperature is between 200°C and 300°C, the steel will be blue brittle, and hammering and bending are prohibited. In general, steels with a carbon content above the range of low carbon steels cannot be hot worked.

(10) Cold forming processing of steel structure: carried out at room temperature. The desired deformation of a material is caused by an external force exceeding the yield strength of the material, or by an external force exceeding the ultimate strength of the material causing some part of the material to separate from the material as required. Cold working makes the material hard and brittle, so the steel can be returned to its normal state by heat treatment, or the hardened edges can be scraped off. Carbon steel shall not be cold worked when the temperature is below -16°C. When the temperature is lower than -12℃, low alloy steel shall not be processed.