1. fabrication and processing of steel structure components

 　　1）Storage of steel

 (1) Site conditions for steel storage: steel can be stored in the open air or in a warehouse with a roof.When stacking in the open air, the site should be flat and should be higher than the surrounding ground, and there should be drainage ditches around; when stacking, the back of the steel section should be upward or outward as far as possible, so as to avoid snow and water accumulation, and there should be a height difference at both ends to facilitate drainage.When it is stacked in the warehouse with ceiling, it can be directly stacked on the floor and padded with corrugated wood.

 (2) Steel stacking requires that the deformation and corrosion of steel should be reduced as much as possible; when stacking steel, the corrugated wood should be placed every 5-6 layers, and the spacing should not cause obvious bending deformation of the steel. The corrugated wood should be aligned up and down in the same vertical plane. It is considered that there is a certain width channel between the material stacking for transportation. 

Stacking standard of steel members

(3) Steel identification plate shall be set up at the end of steel, which shall indicate the steel specification, steel grade, quantity and material acceptance certificate number.The steel ends shall be painted with different colors according to the steel grade.The steel plate should be checked regularly.

 (4) The inspection of steel products must strictly implement the inspection system before the formal warehousing, and the qualified steel products can only go through the warehousing procedures.The main contents of steel inspection include: the quantity and variety of steel are consistent with the order contract; the quality guarantee certificate of steel is consistent with the printed marks on the steel; the specification and size of steel are checked; and the surface quality inspection of steel is carried out.

 　　2）Preparation of steel structure fabrication

 (1) detail design and review drawings the design drawings provided by the general design institute can not be directly used for processing and manufacturing steel structures, but the processing drawings (also known as construction details) should be drawn on the basis of the original design drawings after considering the processing technology, such as tolerance fit, machining allowance, welding control and other factors.The detailed drawing design is generally carried out by the processing unit, and shall be carried out according to the technical design drawings of the construction unit and the specifications, standards and requirements specified in the contract documents.The processing drawing is a detailed drawing which can communicate the intention of designers and constructors. It is the instruction for actual size, marking, cutting, groove processing, drilling, bending, assembly, welding, coating, product inspection, stacking, sending and other operations.The main contents of drawing review include the following items: (1) whether the design documents are complete, including design drawings, construction drawings, drawing descriptions and design change notices.② Whether the geometric dimensions of components are fully marked.③ Whether the dimensions of relevant components are correct.④ Whether the nodes are clear and conform to the national standards.⑤ Whether the number of components in the title block conforms to the project and total quantity.⑥ Whether the connection form between components is reasonable.⑦ Whether the processing symbols and welding symbols are complete.⑧ Considering the equipment and technical conditions of the unit, whether it can meet the technical requirements on the drawings.⑨ Whether the standardization of drawings conforms to national regulations.After drawing review, preparation for technical disclosure shall be made, which mainly includes: 1) considering the butt joint scheme of raw materials and the position of joint in the component according to the component size.② Considering the overall processing technology scheme and important tooling scheme.③ For the unreasonable structure of components or construction difficulties, it is necessary to complete the change visa procedures with the demander or design unit.④ List the key parts in the drawing or places with special requirements, and highlight them.(2) material preparation and check: calculate various materials, specifications and net consumption of materials according to the drawing material list, and propose material budget plan with a certain amount of loss.Generally, the project budget can be increased by 10% according to the actual amount required for material withdrawal and preparation.Check the specification, size and weight of the incoming materials, and carefully check the materials; if substituting materials, the design department must approve and modify them accordingly.(3) the principle of compiling process flow is that the products meeting the requirements of drawing design can be processed reliably with very fast speed, little labor and low cost.The contents include: 1) technical requirements for finished products 

Steel structure processing and production flow chart

　　2）Specific measures: processing methods, precision requirements, inspection methods and inspection tools of key parts; process flow, process quality standards, process measures (such as assembly sequence, welding method, etc.) of main components; processing equipment and process equipment used.The basic contents of the process flow sheet (or process card) are as follows: part name, part number, material grade, specification, number of pieces, process name and content, name and number of equipment and process equipment used, and man hour quota.Key parts should also be marked with processing dimensions and tolerances, and important processes should be drawn out process drawings.(4) technical disclosure shall be organized, and operators shall be trained and assessed, and qualification confirmation shall be conducted for special types of work, and technical disclosure of each process shall be fully done.Technical disclosure can be divided into two levels according to the implementation stage of the project.The first level is the technical disclosure meeting before the commencement of the project. The main participants are: the design unit of the engineering drawings, the construction unit, the project supervision unit and the relevant departments and personnel of the production unit.The main contents of technical disclosure include: 1) project overview; 2) type and quantity of engineering structural parts; 3) description and requirements of key parts in drawings; 4) introduction of nodes in design drawings; 5) requirements for steel and auxiliary materials and quality requirements for docking of raw materials; 6) description of technical standards for engineering acceptance; 7) description of delivery period and delivery method; 8) packaging and transportation of componentsThe requirements are as follows: transportation requirements; 9) coating quality requirements; 10) other technical requirements to be explained.The second level is the disclosure meeting for the construction personnel of the factory before feeding and processing. The participants mainly include: the technical and quality directors of the production unit, the technical personnel and quality inspection personnel of the technical department and the quality inspection department, the person in charge of the production department, the construction personnel and the representatives of the relevant work procedures.In addition to the above 10 points, the main contents of such technical disclosure shall also include process scheme, process specification, construction key points, control method of main process, inspection method and other contents related to actual construction.(5) the safe work of steel structure production, the production efficiency of steel structure is very high, the workpiece moves in a large number of space, and the mechanical equipment used in each process must be protected and protected.Therefore, the safety measures in the production process are very important, especially in the production of large and super large steel structures, more attention must be paid to the prevention of safety accidents.Operators and production management personnel entering the construction site shall wear labor protection articles and operate according to the regulations.Safety learning and safety education shall be conducted for operators, and special types of work must be employed with certificates.In order to facilitate the fabrication of steel structure and the operation of operators, the components should be measured at a certain height.The assembly jig, welding jig and various shelving frames shall be 0.4 ~ 1.2m away from the ground.The stacking and shelving of components should be very stable, and support or positioning should be set if necessary.The stacking of components shall not exceed two layers.The rigging and spreader shall be inspected regularly and shall not exceed the rated load.The normal wear wire rope should be replaced according to the regulations.The strength calculation should be carried out for the manufacturing and installation of all kinds of moulds in the fabrication of steel structures, not only based on experience.The oxygen, acetylene, propane and power supply used in the production process must be provided with safety protection measures, and the leakage and grounding conditions shall be detected regularly.The corresponding signs, signals and warnings shall be made for the hazard sources on the construction site, and the operators must strictly abide by the safety operation regulations of each post to avoid accidental injury.The lifting of components should follow the command of one person.When the component moves, no one is allowed to stay or pass through the moving area.The safe passage of all production sites must be unblocked. 

 　　3）The technological process of steel structure processing and manufacturing (1) the sample rod and sample plate can be made of iron sheet or plastic plate with thickness of 0.50-0.75mm. The accuracy requirements are shown in table 6-2.The sample bar is usually made of iron sheet or flat iron, and wood ruler can be used when the length is short.The sample rod and sample plate shall be marked with job number, drawing number, part number, quantity, processing edge, groove position, bending line and bending direction, hole diameter and rolling radius, etc.The sample pole and sample shall be kept properly until the end of the project.(2) check the specification, material and batch number of steel, and remove the oil, soil and dirt on the steel plate surface.There are four marking methods: centralized marking method, nesting method, statistical calculation method and unified marking method for surplus materials.If the surface quality can not meet the quality requirements, the steel should be corrected. The steel and parts should be corrected by plate machine or profile straightener. The thicker steel plate can also be heated by press or flame. The manual hammering method should be gradually cancelled.When the ambient temperature of carbon structural steel is lower than – 16 ℃ and that of low alloy structural steel is lower than – 12 ℃, cold correction and cold bending shall not be carried out.After correction, the steel surface shall be free from obvious concave surface and damage, and the surface scratch depth shall not be greater than 0.5mm, and shall not be greater than 1 / 2 of the negative allowable deviation of the steel thickness. 

All kinds of mechanical equipment used in steel structure processing and production

(3) the marking shall be made by processing drawing, sample bar, template and steel tape.At present, some advanced steel structure processing plants have adopted program-controlled automatic marking machine, which is not only efficient, but also accurate and material saving.There are two main points of marking: ① the marking operation site should be indoor which is not directly affected by sunlight and external temperature, which is a good open and bright place.② The accuracy of marking with a marking needle is higher than that with an ink ruler and a line.The needle can be sharpened with grinding wheel, and the thickness can reach about 0.3 mm.There are three ways to mark: first line, then line, generally first line and other end after line.Cutting allowance and cutting allowance should be considered when marking the blanking part.(4) steel cutting includes gas cutting, plasma cutting and other high-temperature heat sources, as well as cutting, cutting, friction heat and other mechanical forces.The cutting capacity, cutting accuracy, cutting profile quality and economy should be considered.(5) edge processing and end processing methods mainly include: spading, planing, milling, carbon arc air gouging, gas cutting and groove machining.Shovel edge: there are manual and mechanical shovel edge.The vertical error of edge angle after cutting edge shall not exceed ι / 3000 of chord length, and shall not be greater than 2mm.Edge planer: the equipment used is edge planer.There are two kinds of planing edge processing: plane straight edge and plane inclined edge.The machining allowance of general edge planing is 2-4mm.Edge milling: the equipment used is edge milling machine with high efficiency and low energy consumption.Carbon arc gouging: the equipment used is air gouging gun.High efficiency, no noise, flexible and convenient.Groove processing: generally, gas processing and mechanical processing can be used. In special cases, manual gas cutting method is adopted, but post processing, such as grinding, must be carried out.Now the special machine for groove processing has begun to be popularized. Recently, special machines for H-beam groove and arc groove have appeared, with high efficiency and high precision.The welding quality is directly related to the accuracy of groove processing. If the groove surface is rough and has sharp and deep notch, it is easy to produce non melting parts during welding, and welding cracks will be produced afterwards.For example, in the groove surface adhesion oil, welding will produce pores and cracks, so we should pay attention to the amount of groove. 

 (6) in the welding structure, welding shrinkage and deformation will inevitably occur. Therefore, in the production process, it will greatly affect the product accuracy to grasp when to open the hole.Especially for the engineering of column and beam, the dimensional accuracy of the hole group at the connection part directly affects the accuracy of the steel structure installation. Therefore, it is very important to grasp the opening time. Generally, there are four situations: the first is to mark the hole position at the top of the component processing, and then mark the line to confirm the drilling process after the completion of assembly, welding and deformation correction.The second method is to drill holes at one end of the component, and then to drill holes on the other end after assembly, welding and deformation correction are completed.The third kind: after the component welding and deformation correction, finish the end face, and then take the finishing surface as the benchmark, draw lines and punch holes.Fourth: when marking, the welding shrinkage, allowance of deformation and allowable tolerance are considered, and the drilling is carried out directly.Mechanical drilling has electric drill and pneumatic drill, vertical drilling machine, radial drilling machine, truss radial drilling machine, multi axis drilling machine, NC drilling machine.A simple method for gas tapping is to install a simple accessory device on the gas cutting nozzle, which can make a hole of φ 30.Drill the hole with jig and plate stack.This is a kind of drilling method which has not been popular in China at present. It should be fixed by fixture and the drill sleeve should be made of carbon steel or alloy steel.If T8, gcr13 and GCr15 are made, the hardness of drill sleeve after heat treatment should be higher than that of drill bit hrc2-3.The upper and lower planes of the drilling template shall be parallel, and the deviation shall not be greater than 0.2mm. The center of the drilling sleeve shall be vertical to the plane of the drilling template, and the deviation shall not be greater than 0.15mm. The allowable deviation of the overall drilling formwork manufacturing shall meet the relevant provisions.CNC drilling: in recent years, the development of CNC drilling has updated the traditional drilling method, without marking on the workpiece, proofing and punching, the whole processing process is automatic, high-speed CNC positioning, digital control of bit stroke, high drilling efficiency and high precision.After drilling, the burr on the hole edge shall be removed by polishing machine, and the base metal shall not be damaged. 

 (7) the assembly methods of steel structure include ground sample method, copying assembly method, vertical installation method, horizontal installation method and tire mold assembly method.Ground sample method: the real samples of components are set out on the assembly platform with a ratio of 1:1, and then assembled into components according to the position of parts on the actual samples.This assembly method is suitable for truss, frame and other small batch structure assembly.Copying and copying assembly method: first, assemble the single side (single piece) structure with the ground sample method, then fix it by spot welding, turn it over to be a duplicate tire mold, and assemble another single side structure on it, and assemble it twice.This assembly method is suitable for truss structures with symmetrical cross sections.Vertical assembly method: according to the characteristics of the components and the stable position of the parts, the top-down or bottom-up assembly sequence is selected.This assembly method is suitable for the structure with stable placement, small height or large diameter cylinder.Horizontal installation method: the component is placed in the horizontal position for assembly.It is suitable for slender members with small section but large length.Tire mold assembly method: the assembly method of positioning the component parts on its assembly position with the tire mold.This assembly method is suitable for manufacturing products with large quantity and high precision.The assembly must be carried out according to the process requirements. When there are hidden welds, welding must be carried out first, and the covering can only be carried out after passing the inspection.In order to reduce the deformation, small parts should be assembled and welded as much as possible, and then large parts should be assembled after correction.The assembled parts and components shall pass the inspection, and the rust, burr, dirt, ice and snow, oil stains, etc. on the connecting contact surface of parts and components and the range of about 30-50 mm along the weld edge shall be removed.The splicing of plates and profiles should be carried out before assembly; the assembly of components should be carried out after the assembly, welding and correction of components, so as to reduce the residual stress of components and ensure the production quality of products.The concealed parts of components shall be coated in advance.The allowable deviation of steel member assembly is shown in the code for acceptance of construction quality of steel structures (GB 50205-2001).

 (8) welding is the key step in the fabrication of steel structure.

 (9) treatment of friction surface the value of anti sliding coefficient after treatment of friction surface of high strength bolt shall meet the design requirements (generally 0.45-0.55).Sand blasting, shot peening, pickling, grinding wheel grinding and other methods can be used for friction surface treatment. Generally, the design requirements shall be followed. If there is no design requirement, the construction unit can adopt appropriate methods for construction.When the grinding wheel is used to grind the friction surface, the grinding range should not be less than 4 times of the bolt hole diameter, and the grinding direction should be vertical to the force direction of the component.The friction joint surface of high strength bolt shall not be coated. After the installation of high strength bolt, the surrounding of connection plate shall be closed before painting.(10) the ambient temperature of coating and numbering coating shall meet the requirements of the coating product specification. If there is no regulation, the ambient temperature shall be between 5 and 38 ℃, and the relative humidity shall not be greater than 85%. There shall be no condensation and oil stain on the surface of the component. It shall be protected from rain within 4 hours after coating.The derusting method and derusting grade of steel member surface shall comply with the specification, and the quality requirements shall comply with the national standard rust grade and derusting grade of steel surface before coating.The derusting method and derusting grade of the component surface shall be suitable for the coating used in the design.It is not allowed to paint the parts which are not coated in the construction drawing, the 30-50 mm wide range of the installation weld and the friction connection surface of high-strength bolts.The coating, coating times and coating thickness shall meet the design requirements.After coating, the components shall be numbered according to the design drawings, and the number position shall be in accordance with the principles of convenient stacking, installation and inspection.For large or important components, marks such as weight, center of gravity, hoisting position and positioning mark shall be marked.The summary data of serial number shall be unified with transportation documents, construction organization design documents and quality inspection documents, and the number can be recoated after completion acceptance.The main process of steel structure processing and manufacturing is drawing, marking, setting out, cutting, groove processing, drilling, assembly (including correction), welding, friction surface treatment, coating and numbering.