With the continuous development of modern society and economy, the quality of people's living quality has been continuously improved, and the living environment, living conditions and living needs of human beings are also constantly changing. In the country, the control of the land use system is becoming more and more strict. is getting thinner. Buildings are increasingly developing towards super high-rise buildings, and reinforced concrete structures can no longer meet the needs of building benefits, building structures, construction design and some special functional requirements. Steel structures are widely used in high-rise buildings because of their light weight, high strength, good plasticity and toughness, easy fabrication and short construction period.

1. Introduction: Since steel structure engineering is generally used as the core part and stressed structure of high-rise buildings, its quality directly affects the safety, structure and durability of the building. Cause huge economic losses and heavy casualties. Therefore, the construction steel structure project is listed as a special project, and the national and local construction departments attach great importance to the quality of the steel structure project, and accordingly formulate and promulgate a variety of specifications, standards and technical regulations including and sub-projects. Many experts in the industry have devoted themselves to research in this area for many years, and have written a large number of monographs and documents from different perspectives, making great contributions to steel structure engineering from design to construction, from new technology to the application of new technologies.

The development of the construction industry in recent years is also obvious to all. Architectural engineering is not only a place to meet people's work, life and living functions, but also a highlight of urban construction and a landscape of the city. The main trend of development and city business card. With the increasing popularity of high-rise buildings, steel structure engineering is increasingly taking advantage of its advantages of fast construction speed, short period, saving formwork, high strength, fast construction, and easy prefabrication installation, so it is more and more widely used in engineering. In this regard, the state has compiled the "Code for Construction Quality and Acceptance of Steel Structures" and "Welding Regulations for Steel Structures" according to the construction characteristics of building steel structures. At the same time, experts and scholars in some industries have also compiled relevant steel structure-related industries and corporate standards. For example, China State Construction Engineering Corporation has compiled "Steel Structure Processing Technology", etc. Although various standards and regulations have been issued and operated, there are often some steel structure projects that have problems of one kind or another, such as cracks in steel structure projects, components Surface paint peeling off and other similar quality problems, although very few of them involve raw materials, because once raw materials have problems, it will directly affect the safe use of buildings. Most of them are engineering quality problems caused by production, processing and construction and installation problems. To eliminate the common quality problems of steel structure engineering is a huge systematic project, and it is necessary to pay enough attention to each stage of the construction process, all parties involved in the construction, and each process and link of the design and construction. At the same time, the promotion and application of new technologies and processes of steel structures should also increase publicity efforts, so that everyone can truly feel the importance of the steel structure engineering office to people's living, living and working relationships, and maximize the control of common quality problems. and be eliminated.

2. Analysis of quality problems in steel structure engineering There are many reasons for the difficulty in guaranteeing the quality of steel structure engineering, and they are very complicated. There are not only problems caused by improper process, but also problems caused by violation of process operation. The problems caused by responsibility, and the quality problems caused by the mistakes of decision makers. This article mainly analyzes the problems that are most likely to occur in the production process of building steel structures. I hope everyone can get a little inspiration from it: (1) Problems in the steel itself When a unit is processing a 1200*1200*60 box-shaped column in a building , During the welding process, it was suddenly found that the 60mm thick plate as the web had a tearing phenomenon. The clear cracks were visible to the naked eye and divided the plate into two halves from the thickness direction. After NDT inspection, it was found that the crack depth occurred at a depth of about 3mm. The parts cut from several other plates of the same batch number were tested, and it was found that there were interlayers in the plates, and the poor rolling quality was the main reason for the quality problem. During the welding process, the material of the interlayer is pulled apart due to the welding stress generated by the welding. As a result, the thick plate is torn in the thickness direction. Analysis of the reasons: Due to the particularity of the parts used, this part is used as a web in the component, and the parts welded in the vertical and up-down directions are the stiff plates with full penetration grooves in the welding form. delamination, the welding stress caused by welding is released outwardly to tear the plate in the thickness direction.

he following measures should be taken according to the actual situation: (1) A large number of interlayers in the steel are quality problems caused by the steel mill itself during the rolling process, which have exceeded the requirements of national standards and specifications, and the steel mill can be required to Send someone to verify and negotiate with the steel mill to return or exchange goods; (2) If the number of interlayers is small, the technical department and the owner can be consulted, the information will be fed back to the steel mill, and construction remedial measures can be taken for problems that arise. As a result of non-destructive testing, gouging is used to gouge all the problematic parts to exceed its own depth, and then fill it with equal-strength welding materials. After completion, the surface is treated, and NDT testing is performed after a specified time. (3) Under the witness of the supervisor, cut off the parts and replace them with plates that meet the conditions. The replaced parts are used for non-load-bearing and non-important parts. Parts or used as auxiliary materials, after the completion of the NDT test after the specified time, make a record.

Possible corrective plans and measures to prevent similar quality problems: (1) In signing the purchase contract of steel, special requirements for flaw detection are put forward for the purchased steel, which will increase the purchase cost. But stop at the source to avoid economic losses. (2) For steel plates that have been purchased but have not yet entered the production process, 100% NDT testing shall be performed on the raw materials in the stockyard before the opening of the materials to avoid predetermined losses during the opening and processing. Loss control before it enters the production process. (3) Z-direction performance test and physical and chemical test are carried out for thick plates with special requirements for special parts, and the quality of the materials is recognized. (4) Prepare reasonable process documents. For the welding process, especially for the medium and heavy plates with full penetration welding, a reasonable processing and manufacturing process is adopted. Supervise and control the technical level of welding personnel, welding direction, welding sequence, insulation measures during welding and interlayer temperature control, etc., and take various guarantee measures to prevent welding defects caused by welding construction.

(2) Problems in the construction process The processing process of steel structure is generally: lofting → blanking → milling end → drilling → calibration → assembly → welding → calibration → grinding → rust removal → coating → stacking, etc. According to the national codes, technical standards and the supervisor's requirements for steel structures, combined with my nearly ten years of work experience on steel structure construction sites, quality problems are more likely to occur during the processing and production process and are difficult to handle after they occur, mainly due to special processes and important processes. The proportion of quality problems in general processes is very small. In the above construction process, special processes include welding and painting, and important processes include blanking and assembly. 1. Welding process. This process is a hidden project and one of the most prone to quality problems. Statistics from a company's product quality report in 2004 show that among the quality problems in this process: the weld repair rate caused by welding quality is as high as 80% or more. , followed by the improper operation of the previous process and the technical problems of the operators, which lead to about 10% of the weld quality problems. This problem is the main problem that directly affects the quality of the project. Therefore, this type of problem must be passed by a professional testing company. Generally, according to the types of defects in the weld, it can be divided into slag inclusion, unfusion, pores, etc.

Analysis of the reasons: (1) In the X-type groove penetration weld, during the welding process, due to the incomplete root cleaning on the reverse side, there is a quality problem in the weld. (2) V-type groove welding of the backing plate, because the oxide scale, rust, oil stains, etc. on the surface of the backing plate on the side of the backing plate close to the welding seam are not cleaned or not completely removed, the welding is directly applied on it, and then passed (3) Due to the unreasonable preparation of process documents, such as the welding position is narrow and the working face cannot be unfolded, the design of the groove size does not meet the construction requirements, and the welding current used in the welding process is not suitable. Satisfying the requirements, uncorrectable deformation caused by incorrect welding procedures, processing of medium and heavy plates without preheating, improper insulation measures during welding and improper control of interlayer temperature, etc. (4) During the welding process of the components, the welding quality requirements are met due to the unreasonable welding method. When manual bottoming of the welding seam is used, the submerged arc automatic welding cover operation is performed because the welding quality itself does not meet the requirements; the welding wire flux used for submerged arc automatic welding is not baked and temperature controlled as required; due to the responsibility of the welding operator Not strong enough to cause defects on the surface of the weld.

The following measures can be taken according to the specific situation: (1) Prepare correct process documents, especially for components welded by medium and thick plates, formulate relevant welding process evaluations in combination with specific engineering structure characteristics, and do a good job in the test process. In the record, for the future construction experience. The size of the groove, the reserved gap, etc. are strictly determined according to the national standards. Ensure the accuracy, operability, economy and suitability of the formulation of process documents. (2) The selection of welding materials must be determined through the welding process qualification test and national standards. During the construction process, the use requirements must be strictly in accordance with the national standards for storage before use and baking during use. The heat preservation temperature must be controlled within the specifications required. within the temperature. (3) During the installation and welding process, the rust, oil stains, oxide scale, etc. on the surface of the welding parts must be cleaned up to ensure that the basic work is done well during the construction and welding process. Ensure that the surface treatment of the welding base is good. (4) The reverse side that needs to be cleaned during welding must be cleaned thoroughly and cleanly to ensure that the weld meets the design requirements.

2. Coating process. This process is also a hidden process, and the impact on the structure is less than the impact on the building function. It is also a process that is more prone to quality problems. The quality problems of the process are mainly manifested in: the paint film on the surface of the component falls off in large areas and locally, the paint film on the surface of the component falls off and sags, the thickness of the paint film is not enough, the thickness of the paint film is unevenly distributed, and the color of the paint film is different. larger. Analysis of the reasons: (1) The basic treatment on the surface of the component is not thorough, and there are rust, oxide scale or oil stains, etc., which do not meet the roughness requirements of the component surface, so the adhesion is not strong, especially for projects with strict coating requirements. The components must meet the process and design requirements. (2) Because of the level of construction technology. The construction technology used is relatively backward, and the manual manual operations, such as brushing and rolling, lead to uneven distribution of the thickness of the paint coating, and the touch-up before and after construction results in a large color difference of the paint. (3) During the construction process, avoid quality problems caused by objective factors such as weather and illegal operation of personnel, for example, the temperature and humidity conditions of on-site construction exceed the specified requirements, and the lack of protection for components, etc. (4) Serious irregularities in paint coating caused by rushing the construction period and rushing tasks, such problems will lead to major quality hidden dangers and quality safety.

The following measures can be taken to correct and prevent the occurrence of quality problems and avoid potential problems: (1) Before the start of each project, do a good job in the evaluation of the component coating test piece process to determine the measures that should be taken on the surface of the component and The correctness and operability of the preparation of the process documents, the thickness of the paint film, the time for the paint to dry and the surface to dry, and the influence and control of the ambient temperature. (2) Guarantee the interval time and total thickness between primer, intermediate paint and topcoat layer, and carry out construction in strict accordance with the information provided by the paint supplier to avoid affecting the paint due to the reaction between different components of the paint. Install the final quality. (3) The sanding quality of the component surface before painting meets the quality requirements. Before spraying paint, the sand, burrs and the places that need to be shielded must be shielded as required. After sanding, the surface of the component must be cleaned two hours later. paint. (4) The components that have just been painted must be protected from rain, sand and dust to avoid contamination on the surface of the components and affect the sensory quality of the components. (5) During the spraying process, it is necessary to prevent stacking with other engineering components of different colors to avoid cross-infection caused by the floating paint components during the spraying process. (6) After the completion of the operation, the cleaning and maintenance work of the spraying equipment should be done in time for the painting tools.

3. Lofting and blanking process. This process belongs to the faucet before the component is processed, and its quality has a direct impact on the next process, and even causes all the parts to be cut to be scrapped. This situation is very common, so before cutting It is very important and necessary to strengthen the quality control of the process. The quality problems caused by this process are mainly manifested in: the long strip and thin plate type parts are deformed greatly during cutting; due to the presence of slag inclusions and uneven distribution of components inside the cutting gas or the plate, the cutting surface appears horse teeth. , nodules, and the depth of the cut marks exceeds the standard; the size of the parts that are cut by gas cutting or sawing without considering the shrinkage and deformation of the subsequent process exceeds the standard; the batch parts are scrapped due to the mistakes in the preparation of process documents; The size seriously exceeds the standard requirements. Analysis of the reasons: (1) The purity of the cutting gas does not meet the requirements, resulting in quality problems on the cutting surface. (2) Because the oxide scale on the surface of the steel bursts when it is suddenly exposed to high temperature, the cutting gun is blocked and the cutting quality is similar to saw teeth, horse teeth, etc. (3) Due to the technical level of the operator, there are quality problems such as the not straight cutting line and the inclined cutting surface during manual operation; (4) Due to the uneven force, the elongated parts are bent. (5) It is related to the orbit of the operating machinery, the degree of use and precision of the instrument. For example, in the cutting process, due to the long service life of the cutting machine, problems such as shaking and bouncing occur during the walking process, which affect the cutting.

he following measures can be taken to correct and prevent the occurrence of quality problems and prevent the occurrence of potential problems: (1) Do a good job of random inspection before setting out the parts in batches, so as to avoid a large number of irreparable remediation; The supervision and inspection system adopted for the template (piece) produced by the component controls the problem before the material is opened. (2) Strengthen the monitoring of the process, strictly implement the "three inspection system" of "operator self-inspection - monitor mutual inspection - special inspector special inspection", do a good job in process record supervision and implementation, and do not allow "three inspections". "system" prevails in form. (3) Do a good job of preheating before cutting to prevent the sudden burst of oxide scale on the steel surface during the cutting process, block the cutting nozzle, and cause defects on the cutting surface, so as to avoid repairing and grinding in the next process. (4) Use automatic and automatic manual labor as much as possible to reduce manual manual operation and reduce the occurrence of human factors. 4. Assembly process. This process occupies an important position in the quality of component processing, and its quality is greatly affected by the previous process, so it is very important to strengthen the monitoring of the process before assembly. The quality problems caused by this process are mainly manifested in: the wrong position of the assembled parts, such as 3450mm into 4350mm; the use of the parts is wrong, the 2# parts should have been assembled, but the 3# parts were assembled; the parts The assembly is wrong in the correct position. For example, the 45mm hole on the board is originally facing outward, but the 45mm is actually installed inward; the assembly gap of the assembled parts exceeds the requirements of the specifications and technical documents, and the gap of 3mm is now 7mm; some parts do not The assembly is carried out after calibration, and the existing deformation after assembly cannot be eliminated; the operator cuts the part privately to save trouble, causing the position of the hole on the part to exceed the standard size; the welding area is not surface-treated; the assembly error caused by the wrong size of the drawing .