1.0.2 the scope of application of this specification includes the construction quality acceptance of single-layer, multi-layer and high-rise steel structures, steel grids, metal pressed plates and other steel structures in construction projects. Steel structures in composite structures and underground structures can be checked and accepted for construction quality with reference to this specification. For steel structures not included in other industry standards, such as corridors, lighthouses, pipe supports, overpass bridges, etc. , construction quality acceptance can also refer to this specification.
1.0.3 steel structure drawings are important documents for steel structure engineering construction and the basic basis for steel structure engineering construction quality acceptance; In the market economy, the requirements of engineering quality in the engineering contract have legal effect, so the stipulations of engineering quality in the contract documents are also one of the basis for acceptance, but the stipulations in the contract documents can only be higher than those in this specification, which is the lowest and most basic requirement for construction quality.
1.0.4 The current national standard "Unified Standard for Acceptance of Construction Quality of Building Engineering" GB 50300 has put forward the principle provisions on the division, acceptance method, acceptance procedure and organization of engineering quality, and this specification is not repeated, so this specification emphasizes that it must be used in combination with the current national standard "Unified Standard for Acceptance of Construction Quality of Building Engineering" GB 50300.
1.0.5 The relationship between the relevant provisions and standards compiled according to the standards, and the role of other relevant standards and specifications shall be reflected in the general provisions of this specification.
2 Terms and symbols
2. 1 Terminology
This specification gives specific terms related to 1 1 steel structure engineering construction quality acceptance, plus the 18 clause given in the current national standard "Unified Standard for Construction Quality Acceptance of Building Engineering" GB 50300. The above terms are all given meanings from the perspective of steel structure engineering construction quality acceptance, but the meanings are not necessarily the definitions of terms. This specification gives the corresponding recommended English terms, not necessarily international standard terms, for reference only.
2.2 symbols
This specification gives 20 symbols and the definition of each symbol. These symbols are referenced in all chapters of this specification.
3 Basic clauses
3.0. 1 This article is to check and accept the qualifications and quality management contents of construction enterprises engaged in steel structure engineering, emphasizing the market access system, which is a new management requirement.
The inspection contents in table A.0. 1 in the current national standard "Unified Standard for Acceptance of Construction Quality of Building Engineering" GB 50300 are more detailed, which can be simplified for steel structure engineering, especially for enterprises that have passed the ISO——9000 family demonstration, and the inspection items can be reduced. For conventional steel structure engineering, the inspection contents in table A.0. 1 of GB 50300 mainly include: quality management system and quality inspection system, enterprise standards for construction technology, professional technical management and professional post certificate, construction qualification and subcontractor qualification, construction organization design (construction scheme), inspection equipment and measuring equipment, etc.
3.0.2 The measuring instruments used in the construction quality acceptance of steel structure engineering must pass the periodic measurement inspection according to the provisions of the Metrology Law and must be used within the validity period of verification.
Different gauges have different use requirements, and the measurement accuracy of the same measuring instrument is different under different use conditions. Therefore, this specification requires the correct operation of measuring instruments in strict accordance with relevant regulations.
3.0.4 According to the current national standard "Unified Standard for Acceptance of Construction Quality of Building Engineering" GB 50300, the acceptance of construction quality of steel structure engineering shall be carried out according to the inspection lot, subdivisional works and divisional (sub-divisional) projects on the basis that the construction unit has passed the self-inspection. Generally speaking, steel structure, as the main structure, belongs to sub-projects, and large-scale steel structure projects can be divided into several sub-projects according to spatial stiffness units; When the main structure contains both reinforced concrete structure and masonry structure, the steel structure belongs to a divisional project; Steel structure subdivisional work is divided according to main types of work, materials and construction technology. This specification divides steel structure engineering into 10 subdivisional work, and each subdivisional work is a separate chapter; Dividing subdivisional work into inspection lots for acceptance will help to correct the quality problems in construction in time, ensure the project quality and meet the actual needs of construction. The division of inspection lot of steel structure subdivisional work follows the following principles:
1 Single-layer steel structure is divided according to deformation joints;
2 Multi-storey and high-rise steel structures are divided according to floors or construction sections;
3 profiled sheet metal engineering can be divided into roof, wallboard and floor;
4 For the acceptance of raw materials and finished products when they enter the site, the inspection lot can be merged or decomposed according to the project scale and the actual situation of feeding;
This specification emphasizes that the acceptance of inspection lot is the smallest acceptance unit and the most important and basic acceptance work. The acceptance of divisional works, subdivisional works and unit works is based on the acceptance of inspection lot.
3.0.5 Qualified inspection lot quality mainly depends on the inspection results of master control projects and general projects. The master control project is an inspection project that has a decisive influence on the basic quality of the inspection lot, so it must all conform to the provisions of this specification, which means that the master control project is not allowed to have unqualified inspection results, which means that the inspection of this project has veto power. General items refer to inspection items that are not decisive for construction quality. 80% of the provisions in this article are determined with reference to the original inspection and evaluation standards and the actual situation of the project.
Considering the sensitivity of steel structure to defects, this article sets the threshold for general deviation items as 1.2 times the deviation limit.
3.0.6 The acceptance of subdivisional work shall be based on the inspection lot. Generally speaking, they have the same or similar properties.
Only the sizes of batches are different, so the collection of related inspection lots constitutes the acceptance of subdivisional work. The conditions for qualified sub-projects are relatively simple. As long as the acceptance documents of the inspection lots that make up the subdivisional work are complete and qualified, the subdivisional work is qualified.
3.0.7 This article gives the treatment methods when the quality does not meet the requirements. In general, the inspection lot is the most basic acceptance unit, and nonconforming products should be found and handled in time, otherwise it will affect the acceptance of subsequent inspection lots and related subdivisional works and (sub) divisional works. Therefore, all quality hidden dangers must be eliminated in the bud as soon as possible, which is also the embodiment of the principle of strengthening acceptance and promoting process control in this specification. The handling of abnormal situations is divided into the following four situations:
The first case: if the main control items or general items of the inspection lot cannot meet the requirements of this specification, they should be handled in time. Among them, serious defects should be reworked or replaced; General defects are solved by renovation and rework.
After the construction unit takes corresponding measures, it should be allowed to re-accept. If the provisions of this specification can be met, the inspection lot shall be deemed as qualified.
In the second case, when individual inspection lots find that the strength and quality of raw materials can't meet the requirements, or there are problems such as cracks and deformation, and the defects are serious or the acceptance parties have great differences on quality, which is difficult to solve through consultation, they should invite qualified legal inspection units to conduct inspection and give inspection conclusions. When the test results can meet the design requirements, the inspection lot can pass the acceptance.
In the third case: if the design requirements cannot be met after inspection and appraisal, but the structural safety and use function can still be met after accounting by the original design unit, the inspection lot can be accepted. Generally speaking, codes and standards give the minimum requirements of safety and function, and the design generally leaves a certain margin on this basis. There is no contradiction between not meeting the design requirements and meeting the requirements of corresponding codes and standards.
The fourth case: more serious defects or defects beyond the scope of the inspection lot may affect the safety and use function of the structure. After testing and appraisal by the legal testing unit, it still can't meet the corresponding requirements of the standard, that is, it can't meet the minimum safety reserve and use function. It must be reinforced according to a certain technical scheme to ensure that it can meet the basic requirements of safe use, but it has caused some permanent defects, such as changing the structural size and affecting some secondary use functions. In order to avoid greater losses, it can be accepted according to the technical scheme and negotiation documents and degraded for use without basically affecting the safety and main use functions. However, it should not be used as a way to despise quality and evade responsibility, which should be paid special attention to.
3.0.8 This article aims at the completion acceptance of the steel structure division (sub-division) project.
4 raw materials and finished products come into play
4. 1 General provisions
4. 1. 1 gives the scope of application of this chapter, and puts forward the premise of "entering the construction site of various sub-projects of steel structure" for the first time, thus clarifying the guiding ideology of hierarchical inspection of main materials, spare parts, finished products and standard parts.
4. 1.2 It is feasible in theory to make uniform provisions on the division of acceptance batches applicable to entry acceptance, but it is really difficult in practice, so this article only says "in principle". This gives the specific implementation units greater freedom, and they can handle it flexibly according to different actual situations.
4.2 steel
4.2. 1 In recent years, the application of steel castings in steel structures (especially long-span spatial steel structures) has gradually increased, so it is absolutely necessary to stipulate their specifications and quality. In addition, the standards of imported steel are different in different countries, so it is stipulated that imported steel should be accepted according to the standards stipulated in the design and contract. This article is mandatory.
4.2.2 In engineering practice, it is not clear which steel products need to be reinspected. This article stipulates six situations of re-inspection, which should be the inspection items of witness sampling and sample delivery.
1 Sampling reinspection of imported steel; When there is a re-inspection report from the national import and export quality inspection department, the re-inspection may not be carried out.
2. Because the steel is supplied to users by transshipment and adjustment, it is easy to produce mixed furnace number, and the material certificate is issued according to the furnace number and batch number, so the mixed batch of steel should be reinspected.
3 thick steel plate has anisotropy (yield point, tensile strength, elongation, cold bending, impact value and other indicators in X, Y and Z directions, and the test in Z direction is the worst, especially the plasticity and impact energy value), so when the thickness of the plate is equal to or greater than 40mm, and it is pulled along the thickness direction, it should be reinspected.
4 For long-span steel structures, steel plates for chords or beams are the main stress components, and re-inspection should be carried out.
5 when the design puts forward the requirement of steel reinspection, the reinspection should be carried out.
6 doubts about quality mainly refer to:
1) When the steel is in doubt about the quality certificate;
2) Steel with incomplete quality certification documents;
3) The items in the quality certificate are less than the steel required by the design.
4.2.3, 4.2.4 The thickness of steel plate and the specification and size of section steel are the main factors that affect the bearing capacity, so it is necessary to spot check the thickness of steel plate and the specification and size of section steel when entering the site for acceptance.
4.2.5 Because many steels are basically stacked in the open air and are corroded by wind, rain and polluted air, pits and flake corrosion will appear on the steel surface, which may be unusable in severe cases. Therefore, this article stipulates the surface defects of steel.
4.3 Welding materials
4.3. 1 Welding materials have great influence on welding quality. Therefore, the welding materials used in steel structure engineering should be selected according to the design requirements, and the products should meet the requirements of current national standards. This article is mandatory.
4.3.2 Because the quality of different production batches is often different, this article clearly stipulates the reinspection of welding materials used in important steel structure projects. The reinspection shall be witness sampling and sample delivery inspection items. "Important" in this article refers to:
1 The safety level of the building structure is Grade I and Grade II welds.
2. The safety level of the building structure is Grade I weld.
3. First-class weld in long-span structure.
4. First-class weld in crane beam structure of heavy-duty working system.
5 design requirements.
4.3.4 Improper storage of covered electrode and flux is easy to get wet, which not only affects the technological performance of operation, but also adversely affects the physical and chemical properties of the joint. Welding materials whose appearance does not meet the requirements shall not be used in the project.
4.4 Fastening standard parts for connection
4.4. 1 ~ 4.4.3 The torque coefficient of the high-strength large hexagon-head bolt connection pair and the fastening axial force (pre-tightening force) of the torsional shear type high-strength bolt connection pair are the most important factors affecting the connection quality of high-strength bolts, and are also the important basis for construction. Therefore, manufacturers are required to conduct inspection and issue inspection reports before leaving the factory, and the construction unit shall conduct re-inspection in time before use and during the product quality guarantee period. The reinspection shall be witness sampling.
4.4. 1 is mandatory.
4.4.4 The manufacturer of high-strength bolt connection pair shall pack and supply according to the factory batch number, and provide the product quality certificate. During storage, transportation and construction, it shall be stored and used in strict accordance with the batch number. Bolts, nuts and washers of different batches shall not be mixed. The surface of the high-strength bolt connection pair is specially treated. Before use, keep it in the factory condition as far as possible to avoid the change of torque coefficient or fastening axial force (pre-tightening force).
4.4.5 The tensile strength of high-strength bolts in steel grid structure with bolted spherical joints is the main factor affecting the bearing capacity of joints, and there is a certain internal relationship between surface hardness and strength. The quality of bolts is ensured by controlling the hardness.
4.5 solder balls
4.5. 1 ~ 4.5.4 This section refers to the acceptance items when welding hollow balls as products. The inspection of solder ball welds shall be carried out in accordance with the current national standard "Ultrasonic flaw detection method and quality grading method of solder ball joint iron grating welds" JBJ/T 3034. 1.
4.6 bolt ball
4.6. 1 ~ 4.6.4 This section is the acceptance item when the bolt ball joint is treated as a product. In practical engineering, the quality problems of bolt ball joints are serious, especially the surface cracks are common, so checking the surface cracks of bolt balls is the focus of this section.
4.7 Sealing plate, cone head and sleeve
4.7. 1, 4.7.2 In this section, the sealing plate, cone head and sleeve in the steel grid structure with bolted ball joints are regarded as products, and the acceptance items will be carried out when entering the site.
4.8 metal clamp
4.8. 1 ~ 4.8.3 In this section, the series of metal pressed plates are regarded as finished products, including single-layer pressed metal plates, insulation boards, gusset plates and other roof and wall enclosure plates and spare parts. When these products enter the site, they shall be accepted according to the requirements of this section.
4.9 coating materials
4.9. 1 ~ 4.9.3 In addition to checking the data and documents, the incoming inspection of paint shall be conducted by opening barrels for spot check. In addition, check the phenomenon of coating crust, caking and gel. We should also compare the model, name, color and expiration date of the paint with the quality certificate.
4. 10 Other
Other materials involved in steel structure engineering must pass the acceptance inspection in principle.
5 steel structure welding engineering
5. 1 General provisions
5. 1.2 The division of inspection lots for steel structure welding works shall meet the inspection requirements for steel structure construction inspection lots. Considering that the number of welds in different steel structure engineering acceptance batches is quite different, in order to facilitate inspection, the welding engineering can be divided into one or several inspection lots.
5. 1.3 Cracks may occur during welding, during the cooling of weld and for a long time afterwards. The possibility of delayed cracks in ordinary carbon steel is very small, so it is stipulated that the appearance inspection can be carried out after the weld is cooled to ambient temperature. The delayed crack delay time of low alloy structural steel weld is longer. Considering the limitations of factory storage conditions, on-site installation progress, process connection, and the gradual decrease of the probability of delayed cracks with time, this specification takes the visual inspection results 24 hours after welding as the acceptance basis.
5. 1.4 This article aims to strengthen the dynamic management of welder's welding quality, and at the same time make the on-site management of steel structure engineering welding quality more intuitive.
5.2 Welding engineering of steel members
5.2. 1 Welding materials have great influence on the quality of steel structure welding engineering. Its selection must meet the requirements of design documents and current national standards. For the welding materials that have passed the acceptance inspection, the production date, preservation state and baking of the products also directly affect the welding quality. This article specifies the selection and use requirements of covered electrode, especially the baking state, which is a necessary means to ensure the welding quality.
5.2.2 Operators with special skills play an important role in national economic construction. In the construction welding of steel structure engineering, welder is a special type of work, and the operation skills and qualifications of welder play a role in ensuring the quality of the project, which must be fully valued. Welders mentioned in this article include manual welders and mechanical welders. Welders engaged in the welding construction of steel structure engineering should take the examination and obtain the corresponding certificates according to the specific types of work of steel structure welding engineering and the requirements of the current national industry standard "Technical Regulations for Welding of Building Steel Structures" JGJ8 1 and other technical regulations.
5.2.3 Because the steel structure engineering can't carry out on-site sampling inspection of welded joints and welded joints, flaw detection can only determine the geometric defects of welds, but can't determine the physical and chemical properties of joints. In order to ensure the engineering welding quality, the welding procedure qualification must be carried out before the component fabrication and structural installation construction welding, and the corresponding construction welding procedure specification should be formulated according to the welding procedure qualification results. This article stipulates the conditions that construction enterprises must carry out process evaluation, and the construction unit shall carry out corresponding process evaluation according to the types of steel structures undertaken and the specific provisions in the current national industry standard "Technical Specification for Welding of Building Steel Structures" JGJ 8 1 and other technical specifications.
5.2.4 According to the different stress conditions of structures, the current national standard Code for Design of Steel Structures (GBJ 17) divides the weld quality into three quality grades. Internal defects can generally be detected by ultrasonic flaw detection and radiographic flaw detection. X-ray inspection has the advantages of intuition and good consistency. In the past, people thought that X-ray flaw detection was reliable and objective. However, X-ray flaw detection has high cost, complicated operation procedure and long detection period, especially for T-joints and fillet joints in steel structures, the X-ray flaw detection effect is poor, and the detection rate of harmful defects such as cracks and incomplete fusion is low. On the other hand, ultrasonic flaw detection has the advantages of simple and fast operation procedure, good adaptability to various joint forms and high sensitivity to crack and incomplete fusion detection. Therefore, many countries in the world use ultrasonic flaw detection to control the internal quality of steel structures, and generally do not use radiographic flaw detection.
With the increasing application of large space structures, the corresponding ultrasonic flaw detection methods and defect classification are given in the current national industry standard "Technical Specification for Welding of Building Steel Structures" (JGJ 8 1). The flaw detection of grid welds shall be carried out according to the current national standards, namely, ultrasonic flaw detection method and quality grading method for welded ball joint steel grid welds JBJ/T 3034. 1 and ultrasonic flaw detection method and quality grading method for bolted ball joint steel grid welds JBJ/T 3034.2.
This specification requires full penetration of the first-level weld 100% inspection, and the local inspection of the second-level weld is designated as sampling inspection. Generally, the steel structure takes a long time to make, and the percentage of flaw detection is not less than 200mm in each place, which is beneficial to ensure the quality of each weld. However, the installation weld of steel structure is generally short, mostly beam-column connection weld, and the length of each weld is between 250 ~ 300mm, so it is feasible to adopt sampling inspection of weld number.
5.2.5 In order to reduce the stress concentration and avoid the excessive size of the leg of butt and fillet welds that require penetration, such as T-joints, cross joints and fillet joints, the requirements of different leg sizes for static load structure and dynamic load structure shall be determined with reference to relevant domestic and foreign codes.
5.2.6 Considering that different quality grades have different requirements for the bearing capacity of welds, it is forbidden to have any defects that seriously affect the bearing capacity of welds. This article will seriously affect the bearing capacity of weld appearance quality requirements into the main control project, given the appearance of qualified quality requirements. Because of the importance of primary weld and secondary weld, there should be specific requirements for surface porosity, slag inclusion, arc pit crack and arc scratch, while defects such as undercut, incomplete penetration and root shrinkage have great influence on dynamic load, so primary weld should not have such defects.
5.2.7 Welding preheating can reduce the cooling rate of heat affected zone, which plays an important role in preventing welding delay cracks and is the focus of building welding codes in various countries. Because the basic work of steel weldability test in China is not systematic enough, there is no condition to put forward the corresponding calculation formula or chart for determining the welding preheating temperature. At present, preheating temperature is mostly determined by process test. At the same time as the preheating temperature, it is necessary to specify the temperature range from the welding part to all directions. The larger the temperature range, the smaller the cooling rate of welding heat affected zone, and the greater the cooling rate. For the same preheating temperature requirement, if the temperature range is uncertain, the preheating effect is very different.
Post-weld heat treatment is mainly to dehydrogenate the weld to prevent cold cracks. The timing and holding time of post-heat treatment directly affect the effect of post-heat treatment, so it should be carried out immediately after welding, and the treatment time should be appropriately increased according to the thickness of the plate.
5.2.8, 5.2.9 Defects such as incomplete penetration, undercut and arc scratch. It is easy to happen in the welding process, and it is strictly forbidden for dynamic load structures, and it should be limited to a certain range in the second and third grade welds. The bearing capacity of steel structure will also be affected by the deviation of the residual height and offset of butt weld, the leg size and residual height of partial penetration butt weld and fillet weld, which must be limited.
5.2. 10 In order to reduce stress concentration and improve the ability of the joint to bear fatigue load, the surfaces of some fillet welds are welded or concave. This kind of joint must pay attention to the smooth transition between weld and base metal. At the same time, the influence of weld shape and size should be considered when determining the calculated thickness of weld.
5.3 Welding items of welding nails (studs)
5.3. 1 Because the composition of steel and the welding quality of welding nails have a direct impact, the welding procedure qualification test must be carried out according to the matching of steel and welding nails used in actual construction. When the porcelain ring is wet or the product requires drying, it should be dried as required to ensure the quality of welded joints.
5.3.2 After welding, the bending inspection of welding nails can be carried out by bending. Welding nails can be welded by special stud welding or other arc welding methods. Different welding methods have different requirements for the appearance quality of the joint. This regulation is aimed at the appearance quality requirements of welded joints of special stud welding machine. Other welding nail joints welded by arc welding can be inspected according to the appearance quality and size requirements of fillet weld.
6 fastener connection project
6.2 ordinary fastener connection
6.2. 1 This article is to reinspect the entrance bolt products. Among them, doubt refers to dissatisfaction with Article 4.4. 1 of this specification, and lack of quality documents such as quality certificate (ex-factory certificate).
6.2.5 Nail shooting should be checked by observation. If you knock with a small hammer, you should knock from the side or front of the nail.
6.3 High-strength bolt connection
6.3. 1 Anti-sliding coefficient is one of the main design parameters of high-strength bolt connection, which directly affects the bearing capacity of members. Therefore, both the manufacturer and the site should test the anti-skid coefficient when dealing with the friction surface of components, and the minimum value of the measured anti-skid coefficient should meet the design requirements. This article is mandatory.
When grinding the friction surface locally with a grinding wheel at the installation site, the grinding range should not be less than 4 times the diameter of the bolt hole, and the grinding direction should be perpendicular to the stress direction of the component.
Except that the friction coefficient is less than or equal to 0.3 in the design, and it is clearly stipulated that the anti-skid coefficient test is not needed, in order to determine the treatment method of the friction surface, three groups of specimens with the same material and the same treatment method must be reinspected in batches according to the requirements in Appendix B of this specification. At the same time, three groups of specimens with the same materials and treatment methods are attached for re-inspection before installation.
6.3.2 When the high-strength bolt is finally tightened 1h, most of the loss of bolt preload has been completed. In the next day or two, the losses stabilized. After more than a month, the loss will stop. However, under the influence of external environment, the torque coefficient of bolts will change, which will affect the accuracy of inspection results. In order to unify and facilitate operation, the inspection time specified in this article must be completed within 48 hours after1h.
6.3.3 The structural reason of this article refers to the situation that the space is too small for final tightening with a special wrench due to design reasons. In the construction of torsional shear high-strength bolts, the installation sequence and direction are not considered well, or there is no experience in using an electric wrench in the final tightening, which leads to the slip at the edge of the tail plum blossom head, and the plum blossom head cannot be unscrewed, resulting in the unknown final tightening torque. For such bolts, a certain proportion should be controlled.
6.3.4 The purpose of initial screwing and re-screwing of high-strength bolts is to make the friction surfaces close to each other, and make the bolts bear uniform force. For large joints, the installation sequence is emphasized to prevent the uneven loss of bolt pretension in the joints and affect the stiffness of the connection.
6.3.7 Forcibly penetrating the bolt will damage the thread, change the torque coefficient of the high-strength bolt connection pair, and even screw on the nut, so it is emphasized to freely penetrate the bolt hole. Gas cutting reaming is irregular, which not only weakens the effective bearing surface of the component and reduces the pressure transmission area, but also causes defects in the steel at the reaming, so it is stipulated that gas cutting reaming is not allowed. The limitation of the maximum reaming amount is also based on the consideration of the effective bearing surface and friction transfer area of the member.
6.3.8 The stiffness (deflection) of grid structure with bolted ball joints is often weaker than the design value, mainly because the high-strength bolts connected with bolted balls and steel pipes are not fastened firmly, and there are gaps and looseness. After the lower support system was dismantled, the deflection increased obviously due to the connection gap and looseness. , which exceeds the limit specified in the specification.
7 steel parts and steel parts processing engineering
7.2 cutting
7.2. 1 The cutting surface or shearing surface of steel shall be free of cracks, slag inclusion, delamination and lack of edges larger than 1 mm ... These defects can be obviously exposed after gas cutting, and can generally be observed (checked with a magnifying glass); However, the situation is different for gas cutting surface or shearing with special requirements. In addition to observation, penetrant, magnetic particle or ultrasonic flaw detection shall be adopted when necessary.
7.2.2 The deviation value of gas cutting in cutting is based on the professional standard of hot cutting, and the allowable deviation of gas cutting is put forward in combination with the limitation of section size and incision depth.
7.3 correction and shaping
7.3. 1 defines the minimum ambient temperature for cold straightening and cold bending, so as to ensure that steel will not produce cold brittle fracture when subjected to external force at low temperature. The brittle fracture of steel under external force at low temperature is more sensitive than that under stamping shear, so the ambient temperature is strictly limited.
7.3.3 In the process of straightening steel and parts, straightening equipment and lifting may have an impact on the surface. According to the allowable degree of steel surface defects, the scratch depth is not more than 0.5mm, and the depth is not more than 1/2 of the negative deviation value of steel thickness to ensure the surface quality.
7.3.4 The minimum radius of curvature and maximum bending height of cold straightening and cold bending are specified according to the characteristics of steel, the feasibility of process and the limitation of appearance quality after forming.
7.3.5 specifies the deviation value of steel after correction molding. Except for the local flatness of steel plate, other indexes are different between acceptable quality deviation and allowable deviation, and strict regulations are made.
7.4 edge treatment
7.4. 1 In order to eliminate the adverse effect of cold work hardening and the thermal effect of cutting on the main reinforcement, and make the edge processing meet the relevant requirements of the design code for the stress value of edge processing and the pressure bar curve, it is stipulated that the minimum planing amount of edge processing should not be less than 2.0 mm
7.4.2 Keep the quality index of two adjacent included angles and the verticality of the machined surface, so as to control the shape of the part to meet the requirements of assembly, assembly and stress, and the deviation of the straightness of the machined edge shall not be superimposed with the dimensional deviation.
7.5 Processing of Tube and Ball
7.5. 1 The bolt ball is a stress member connected with the grid member, and its quality can be easily guaranteed by hot forging. For forged balls, it is important to check whether there are cracks, overlapping marks and overheating.
7.5.2 The welding sphere shall have a smooth surface. Smooth surface should be free of cracks and wrinkles. After the residual height of the weld conforms to the surface quality of the weld, it should be polished and leveled at the joint.
7.5.4 The quality index of solder balls specifies the diameter, roundness, wall thickness reduction and the offset between the two hemispheres. The deviation value is basically consistent with the current national industry standard "Code for Design and Construction of Grid Structure" JGJ 7, but the diameter is slightly increased in the range of φ300mm ~φ500mm, and the roundness is reduced, which is the degree that can be achieved by avoiding the sudden change of control index and considering the amount of misalignment, and it is strictly controlled relative to the large-diameter welding ball to ensure the nozzle gap and welding quality.
7.5.5 The specified deviation values of the length, end verticality and nozzle curve of steel tube members are put forward according to the requirements of assembly, welding and stress of grid members, and the allowable deviation of the straightness of members shall conform to the provisions of the bending and rising correction of steel beams. Check the nozzle curve with a template, and the clearance shall not be greater than1.0mm.
7.6 drilling
7.6.65438+
The Ra in the article is based on the current country.