Steel Structure Plant: A Revolution in Load-Bearing Architecture Steel structure plants are predominantly characterized by their main load-bearing components made entirely of steel. This includes steel columns, steel beams, steel structure foundations, and steel roof trusses. With the expansive nature of modern factories, steel structure roof trusses have become a staple, complemented by steel roofs and, occasionally, brick walls for added support. China's burgeoning steel production has catalyzed the widespread adoption of steel structure plants, which can be classified into light and heavy steel structure categories. Industrial and civil construction edifices built from steel are collectively termed as steel structures. Key features of steel structure plants include: 1) Lightweight yet highly robust construction with extensive spanning capabilities. 2) Short construction periods resulting in reduced investment costs. 3) Superior fire resistance and exceptional corrosion resilience. 4) Ease of relocation and eco-friendly recycling, ensuring minimal environmental impact.
Steel Structure Construction Technology
Scope of Application: This technology is tailored for the processing of building steel structures, encompassing a comprehensive array of procedures including: process flow selection, lofting, marking, cutting, correction, molding, edge processing, tube ball handling, hole making, friction surface treatment, end processing, component assembly, round tube component processing, and pre-assembly of steel components.
1. Material Requirements
1.1.1 Quality Assurance: All steel, welding materials, coatings, and fasteners must come with quality certificates and comply with both design specifications and current standards.
1.1.2 On-Site Inspection: Upon arrival, raw materials must undergo witness sampling, inspection, and acceptance by Party A and the supervisor, adhering to contract stipulations and prevailing standards. Detailed inspection records and reports must be furnished to both Party A and the supervisor.
1.1.3 Defect Management: Any defects discovered in raw materials during processing must be promptly examined and addressed by qualified inspectors and technical experts.
1.1.4 Material Substitution: Any material substitution requests must be submitted in advance with a technical approval sheet and material certificate. These requests require approval from Party A and the supervisor, followed by confirmation from the design unit.
1.1.5 Prohibited Materials: The use of electrodes with a peeling or rusted core, as well as damp, caked, or melted flux and rusty wire, is strictly forbidden. Studs for welding must be free from defects such as cracks, striations, dents, and burrs.
1.1.6 Welding Material Storage: All welding materials must be centrally managed in a dedicated, dry, and well-ventilated warehouse.
1.1.7 Bolt Storage: Bolts must be stored in a dry and ventilated area. High-strength bolts must be accepted per the national standard 'Design, Construction, and Acceptance Procedures for High-Strength Bolt Connections of Steel Structures' (JGJ82). The use of corroded, stained, damp, bruised, or mixed-batch bolts is strictly prohibited.
1.1.8 Paint Storage: Paint must meet design requirements and be stored in a special warehouse. Expired, deteriorated, caked, or ineffective paint must not be used.
2. Main Machinery
Steel Structure
Hai Luo Steel Structure
1.2.1 Main Equipment
Steel Structure Production Tools
3. Operating Conditions
1.3.1 Construction Approval: Detailed construction drawings must be completed and approved by the original designer.
1.3.2 Technical Preparations: All necessary technical preparations, including construction organization design, construction schemes, and operation instructions, must be in place.
1.3.3 Process Evaluations: All process evaluation tests, performance tests, and material purchase plans must be completed.
1.3.4 Material Arrival: All primary materials must have entered the factory.
1.3.5 Comprehensive debugging acceptance of all types of mechanical equipment.
1.3.6 Every production worker has undergone rigorous pre-construction training and has obtained the necessary qualification certificates.
4 Operation Process
1.4.1 Process Flow
1.4.2 Operation Process
1 Lofting and Material Marking
1) Thoroughly familiarize yourself with the construction drawings. Any questions should be promptly addressed by consulting the relevant technical departments.
2) Prepare samples and sample rod materials, typically using thin iron sheets or flat steel.
3) Ensure that the steel ruler for lofting has been verified and approved by the metrological department before use.
4) Understand the material and specifications of raw materials prior to lofting. Check the quality of raw materials and categorize different parts accordingly. Follow the principle of processing larger components before smaller ones.
5) Paint the sample rod with the processing number, component number, and specification. Additionally, mark the diameter of the upper hole, working line, bending line, and other processing symbols.
6) Reserve shrinkage allowances (including on-site welding shrinkage) and machining tolerances required for cutting and milling operations:
Milling End Allowance: Typically, add 3-4mm per side after cutting, and 4-5mm per side after gas cutting.
Cutting Margin: For automatic gas cutting, the slit width is 3mm. For manual gas cutting, the slit width is 4mm.
Welding Shrinkage: As specified by the process, based on the structural characteristics of the member.
7) When marking the material, main force members and those requiring bending should follow the process direction. The outside of bending parts should be free from sample impact points and scars.
8) Marking materials should facilitate cutting and ensure the quality of parts.
9) Identify and label remaining materials after marking, including number, specification, material, and batch number, to facilitate reuse.
2 Cutting
Steel must be cut according to its desired shape and size after the blanking line has been marked.
1) Important considerations during cutting:
(1) When arranging multiple parts on a steel plate with intersecting shear lines, plan a reasonable cutting procedure in advance.
(2) Correct any bending deformation of the material after shearing. Trim and polish rough or burr-laden shear surfaces.
(3) During shearing, metal near the incision is squeezed and bent. The interface positions of important structural parts and welds must be milled, planed, or ground.
2) Key construction points for sawing machinery:
(1) Straighten section steel before sawing.
(2) For single-piece sawing, draw the marking line before cutting. For batch processing, pre-install positioning baffles.
(3) For important components with high machining accuracy requirements, reserve appropriate machining allowances for face finishing after sawing.
(4) Ensure the control of perpendicularity of the cutting section during sawing.
3) Essential Process Points for Gas Cutting Operations:
(1) Prior to commencing gas cutting, ensure all equipment and tools within the gas cutting system are thoroughly checked for optimal operation and safety standards.
(2) Select the correct process parameters for gas cutting. Adjust the oxygen jet (wind line) to maintain a distinct outline, elongated wind line, and high shooting force for precise cuts.
(3) Ensure all dirt, oil, floating rust, and other debris are removed from the steel surface before gas cutting. Leave sufficient space beneath the material to facilitate slag ejection.
(4) Prevent tempering during the gas cutting process by adhering to the correct operational guidelines.
(5) To minimize deformation during gas cutting, begin from the short side. Cut smaller parts first, followed by larger ones, and tackle complex shapes before simpler ones.
3 Correction and Molding Procedures
1) Correction Techniques
(1) Cold correction of finished products typically involves mechanical forces such as flange levelers, straighteners, hydraulic presses, and similar equipment.
(2) Flame correction employs point heating, linear heating, or triangular heating methods.
For low carbon and ordinary low alloy steel, the ideal thermal correction temperature ranges between 600 ~ 900 °C. The optimal temperature for thermoplastic deformation is 800 ~ 900 °C, not exceeding 900 °C.
Medium carbon steel is prone to cracking under deformation, making flame correction generally unsuitable.
Ordinary low-alloy steel should be cooled slowly following heating correction to prevent stress build-up.
Process Flow
2) Molding Techniques
(1) Hot Processing: For low carbon steel, the processing temperature is generally between 1000 ~ 1100 °C, and should not fall below 700 °C. For heating, maintain a temperature of 500 ~ 550ºC. Avoid hammering and bending brittle steel to prevent breakage.
(2) Cold Processing: Conducted at room temperature using mechanical equipment and specialized tools.
4 Edge Machining (Including End Milling)
1) Common edge processing methods include edge cutting, planing, milling, carbon arc gouging, gas cutting, and bevel machining.
2) For gas-cut parts requiring edge processing to eliminate the influence zone, ensure a minimum processing allowance of 2.0mm.
3) The depth of the machined edge must be sufficient to remove surface defects, with a minimum depth of 2.0mm. Ensure the surface remains undamaged and free of cracks, and follow the edge's contours when using grinding wheels.
4) Following manual cutting of carbon structural steel parts, clean the surface thoroughly, ensuring no roughness exceeds 1.0mm.
5) For end members, the planing top must be tight, and the section accuracy of the end must be high. Regardless of the cutting method or steel type, planing or milling is required.
6) Edges of construction drawings with specific welding requirements must be planed. General plate or steel shear edges do not require planing.
7) Post mechanical automatic cutting and air arc cutting, the flatness of the cutting surface must maintain precision, not exceeding 1.0mm. For the main stress members' free edge, ensure a planing or milling allowance of at least 2mm on each side post gas cutting, free from burrs and other defects, guaranteeing a smooth and flawless finish.
8) Post column end milling, the top surface must achieve optimal contact, with more than 75% of the area adhering to the 0.3mm feeler. Any stuffing area should be limited to 25% max, and the edge gap must not exceed 0.5mm, ensuring a tight and precise fit.
9) The selection of milling techniques and the amount of material to be milled should align with the workpiece's material and processing requirements. A judicious choice ensures superior processing quality, vital for achieving excellence in construction.
10) Ensure end processing of components is conducted only after proper correction to maintain structural integrity and precision.
11) Implement necessary measures based on the component's form to guarantee that the milling end remains perpendicular to the axis, ensuring consistency and reliability.
Five-hole system
1) High-strength bolts (large hexagonal head bolts, torsional shear bolts, etc.), semi-round head rivet self-tapping screws, and other holes can be produced through drilling, milling, punching, reaming, or countersinking, providing versatile and robust fastening solutions.
2) Prefer drilling for component holes, with punching permissible only if it is proven that the material's quality, thickness, and aperture will not lead to brittleness.
All standard structural steels under 5mm thickness can be punched. For minor structures with thicknesses under 12mm, punching is also allowed. Avoid welding on punched holes (groove shape) unless it is proven that the material retains significant toughness post-punching. Normally, for larger punched holes, ensure the hole is 3mm smaller than the specified diameter.
3) Before drilling, grind the drill and select the chip allowance wisely to ensure precision and effectiveness.
4) Bolt holes must be cylindrical and perpendicular to the steel surface at the specified location. Ensure the inclination is less than 1/20, and the hole perimeter is free of burrs, cracks, flares, or bumps, with clean-cut edges.
5) For bolt holes made through refining or reaming, the diameter should match the bolt rod's diameter. Post drilling or assembly, the hole must attain H12 accuracy, with a surface roughness of Ra less than 12.5μm.
6 Friction surface processing
1) High-strength bolted friction surfaces can be processed via sandblasting, shot blasting, or grinding with a grinder (note: the grinding direction should be perpendicular to the component's force direction, covering a range not less than 4 times the bolt diameter).
2) Post-treatment, protect the friction surface from oil and damage to maintain its integrity and performance.
3) Both the manufacturer and installation unit must conduct anti-slip coefficient tests for steel structure manufacturing batches. For batches up to 2000t, each treatment process requires separate inspection, with three groups of specimens per batch.
4) Specimens for the anti-slip coefficient test must be processed by the manufacturer. Ensure that these specimens, along with the represented steel structural members, share the same material, batch, friction surface treatment process, surface state, and high-strength bolt connection pairs, and are stored under identical environmental conditions.
5) The specimen steel plate's thickness must be determined based on the representative plate thickness used in steel structure engineering. The surface should be impeccably smooth, devoid of oil, and the hole edges must be free from any flash or burrs to ensure precision and quality.
6) During the steel structure manufacturing process, the manufacturer shall conduct a comprehensive anti-slip coefficient test and provide a detailed report. This report must clearly outline the test methods and results, ensuring transparency and adherence to safety standards.
7) For retesting the anti-slip coefficient, components made from the same material and treatment method must comply with the current national standards 'Design, Construction, and Acceptance Procedures for High-Strength Bolted Connections of Steel Structures' (JGJ82) or the design document provisions. These components should be handed over simultaneously to maintain consistency and reliability.
7) Tube ball processing
1) Rod production process: From the initial purchase of steel pipes to the final anti-corrosion treatment, each step is meticulously planned: purchase steel pipe → inspect material, specifications, surface quality (including anti-corrosion treatment) → cutting and beveling → spot welding with cone head or seal plate assembly → welding → inspection → pre-anti-corrosion treatment → final anti-corrosion treatment.
2) Bolt ball manufacturing process: Starting with steel bars (or ingots) for pressure processing or round steel for machining, the process involves: forging the blank → normalizing treatment → processing the positioning thread hole (M20) and its surface → creating each thread hole and plane → marking with worker and ball numbers → pre-anti-corrosion treatment → final anti-corrosion treatment.
3) Cone head and sealing plate production process: The journey from finished steel blanking to mechanical processing involves: die forging → normalizing → mechanical processing, ensuring high precision and quality.
4) Welding ball joint grid manufacturing process: Starting with the steel pipe, the process includes: inspection of material, specifications, and surface quality → lofting → cutting → hollow ball production → assembly → anti-corrosion treatment, ensuring robustness and durability.
5) Welding hollow ball production process: This intricate process includes: blanking (with copying cutter) → pressing (heating) molding → machine tool or automatic gas cutting groove → welding → weld non-destructive inspection → anti-corrosion treatment → packaging, guaranteeing the highest quality and safety.
8) Assembly
1) Prior to assembly, it is crucial that staff thoroughly familiarize themselves with the construction drawings and related technical requirements. The quality of parts to be assembled must be reviewed meticulously according to the construction drawings.
2) In cases of insufficient size of raw materials or specific technical requirements, parts must be spliced prior to assembly to ensure seamless integration and structural integrity.
3) The following guidelines must be adhered to when using mold assembly:
(1) The selected assembly site must be smooth and possess sufficient strength to support the process.
(2) While arranging the assembly mold, it is essential to account for prerelease welding shrinkage and other processing allowances based on the characteristics of the steel structure members.
(3) After assembling the first batch of components, a comprehensive inspection by the quality inspection department is mandatory. Only after passing this inspection can the assembly continue, ensuring consistent quality.
(4) Components must be assembled strictly according to process regulations. For hidden welds, they must be welded first and covered only after passing inspection. For complex parts that are challenging to weld, a weld-while-assembling method can be employed to complete the assembly efficiently.
(5) To minimize deformation and optimize the assembly sequence, a method of initial assembly into components followed by final assembly into larger units can be adopted, enhancing precision and efficiency.
4) The assembly method selection for steel structure components must be grounded in the structural characteristics and technical requirements of the components. This, combined with the manufacturer's processing capacity and available mechanical equipment, should guide the choice of the most efficient and quality-controlled assembly method.
5) Typical structure assembly
(1) Welding H-beam construction technology
Process flow
Cutting → assembly → welding → correction → secondary cutting → hole making → welding other parts → correction and grinding, ensuring a seamless and robust final structure.
(2) Advanced Processing Technology for Box Section Components
(3) Precision Processing Techniques for Rigid Cross Columns
(4) Comprehensive Pipe Rolling Process Flow Chart
1) Pre-assembly Quantity: Must adhere strictly to design requirements and technical documentation.
2) Pre-Assembly Component Selection Principle: Focus on the main stress frame, especially where joint connections are complex, component tolerances are near limits, and the components are representative of composite structures.
3) Pre-assembly must be conducted on a robust and stable platform tire frame, ensuring the bearing point levelness adheres to specified standards:
A≤300 ~ 1000m2 Tolerance ≤2mm
A≤1000 to 5000m2 Tolerance < 3mm
(1) During pre-assembly, all components must be aligned with construction drawings. The center of gravity line of each bar should converge at the center of the node, remaining in a completely free state with no application of external force. Each single member, whether column, beam, or support, must have at least two supporting points.
(2) Pre-assembled components must have a control basis, with the center line clearly marked and consistent with the platform and ground baselines. Any necessary changes to the pre-assembly basis position must receive approval from the process design team.
(3) All components set for pre-assembly must be single components that have passed inspections by special inspectors, meeting all quality standards post-production. Each identical single member should be interchangeable without affecting overall geometry.
(4) Throughout the pre-assembly of the tire frame, components must not be modified or cut using flames or machinery. Nor should heavy weights be used for ballast, collision, or hammering.
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