This paper analyzes the main characteristics of steel structure welding construction in high-rise buildings and the main factors affecting welding quality, points out the difficulties in steel structure installation and welding construction in high-rise buildings, and puts forward the main measures to control welding quality according to the author's years of working experience.
Keywords: high-rise building; Welding; Quality management; quality management
In China's (super) high-rise buildings, steel structures are widely used because of their many advantages. It can be predicted that various forms of steel structure will become the dominant structure in buildings with more than 50 floors in the future. Steel structure engineering involves a wide range and is technically difficult. Steel structure technology has become a new technology in the construction industry and has been popularized and applied. Among them, welding technology is one of the key construction technologies, and welding quality is often the focus and difficulty of construction quality control. This paper analyzes the characteristics of high-rise steel structure welding construction and the main factors affecting welding quality, and puts forward the main measures to control welding quality.
1, the main characteristics and difficulties of steel structure installation and welding construction in high-rise buildings
1. 1 Main features of welded structure
1. 1. 1 aerial work;
1. 1.2 outdoor operation;
1. 1.3 has a long construction period;
1. 1.4 high-strength alloy steel is widely used. Such as China 16Mn, Japanese SM4 1, SM50, SM53, American A36, A572, etc.
1. 1.5 uses a lot of thick plates and ultra-thick plates;
1. 1.6 In addition to traditional manual arc welding, CO2 gas shielded semi-automatic welding, 20CO2+80%Ar: mixed gas shielded semi-automatic welding, self-shielded flux-cored wire welding and automatic welding are widely used;
1. 1.7 requires high welding quality, and generally adopts semi-penetration and full penetration welds.
1.2 main difficulties in welding construction The above characteristics bring a series of difficulties to welding construction, mainly including:
1.2. 1 windy working environment;
1.2.2 temperature and humidity change greatly, even rain and snow threaten, low-temperature welding construction, etc.
1.2.3 The welding workload is heavy and the welding repair is difficult;
1.2.4 The workload of auxiliary operation is heavy;
1.2.5 Free welding space is limited;
1.2.6 has a large amount of cross work with other types of work (such as hoisting, high-strength bolt connection construction, etc.). );
1.2.7 welding cracks tend to be serious, and some thick plate structures tend to tear by layers;
1.2.8 large welding deformation.
In addition, due to the short development time of high-rise building steel structure in China, the design and construction standards of high-rise building steel structure in China are not perfect at present, and foreign design, foreign materials, foreign general contracting construction and foreign standards are often adopted, which leads to the lack of unified standards for welding quality control and brings difficulties to welding construction quality control.
2, the main measures of welding quality control
According to the analysis of the above factors affecting welding quality, combined with engineering practice, the main measures of quality control are as follows:
2. 1 When making the welding construction scheme, technical and economic analysis should be made according to the actual situation and technical requirements of steel structure installation on site, and a feasible welding construction scheme should be made. The plan should include and confirm the following main items.
2. 1. 1 Methods, materials and personnel to manage welding conditions; Welding method; Use steel (reinspection); Welding materials and their management; Welder training, examination and management; Quality control organization; Quality control system; Protective measures; Security measures.
2. 1.2 processing. Groove essentials; Key points of groove processing; Installation points of arc striking plate; Assembly and welding sequence.
2. 1.3 assembly. Preheating essentials; Arc striking plate treatment; Key points of positioning welding; Root-clearing essentials; Welding seam and processing essentials; Post-heat essentials; Corrective points when bad things happen; Key points of welding repair.
2. 1.4 check. Standards, methods and key points of appearance inspection; Methods, standards and key points of nondestructive testing.
2.2 Preparation before welding Quality control Carefully prepare before welding. "Getting ready before welding is half done!" The following items shall be confirmed before welding.
2.2. 1 environment. Working environment; Welding environment; Safety and health precautions.
2.2.2 Materials and appliances. Power supply capacity; Type and combination of welding materials; State of welding material; Use device status.
2.2.3 Processing and assembly. Groove shape; Groove size; Root gap; The wrong side; Installation status of the back pad; Positioning welding; Installation status of arc striking plate.
2.2.4 Others. Cleaning and machining of welding groove surface; Preheat.
2.3 Quality control in the welding process During the welding process, the welder should strictly follow the requirements of the welding scheme and welding process instruction, strictly abide by the process discipline, and confirm the following items.
Welding sequence; Welding power supply; Arc voltage; Welding speed; Mode of transportation; Setting method of weld; The position of the arc; Welding state of the front layer; Root cleaning; Interlayer temperature; Covered electrode or the choice of welding wire diameter; After heating and heat preservation.
2.4 Post-weld quality control After welding, the weld shall be strictly inspected according to the design requirements and relevant standards to confirm the appearance, size, surface and internal defects of the weld. The main projects are:
2.4. 1 Appearance and surface defects Whether the weld surface is regular; Press the pit; Welding burr; Pendant; Bite the edge; Crater state; Surface stomata; Surface crack.
Size. Excess height dimension; Welding length; The length of fillet weld leg and the size of reinforced fillet weld; Unequal side length of fillet welding.
Internal defects. Cracks; Not fused; Incomplete penetration; Slag inclusion; Stomata.
2.4.4 Processing. Treatment of arc striking plate; Whether splash removal is qualified; Welding around the end; Welding repair.