Where should Zhongshan recruit stainless steel welders?

There are some common and common faults in the fabrication and installation of steel structures, which are mainly manifested in the following aspects:

First, the joint examination of design drawings is not in place

The responsibility of the construction unit is to carry out construction according to the drawings, but it is also the responsibility of the construction unit to conduct joint examination of the construction drawings before construction, so as to bring forward the aspects that appear in the design drawings that are imperfect, unclear, unsuitable for construction and inconsistent with the specifications (especially for mandatory provisions). If the problems found are not raised, the project will bring difficulties in the construction process and acceptance, and the construction quality will be difficult to be guaranteed, resulting in hidden dangers.

When we check the engineering quality, we often find the following problems in the design drawings:

First, the application specifications of the design drawings are incomplete and incorrect.

If some design instructions use outdated and abolished standards; Some materials are incomplete in brand and grade, and the marks of high-strength bolts, ordinary bolts and welding connection points are unclear or not displayed. The specifications, models and performance of all kinds of high-strength bolts, ordinary bolts, studs, rivets and their washers are not specified, but they have been included in the acceptance specification for steel structure construction quality and are required as mandatory provisions. If the design drawings are not specified, there will be no basis for construction and acceptance, resulting in blind construction and unacceptable acceptance.

second, the general design description does not specify the safety level and service life of the project.

different safety levels of projects have different requirements for construction inspection such as welding. If the safety level is Grade I, the welding materials of Grade I and II welds must be re-examined; If the safety level is Grade II, the welding material of Grade I weld must be retested, but the welding material of Grade II weld does not necessarily need to be retested.

thirdly, the material grade of steel, and the friction test requirements of high-strength bolts are not clear.

some design drawings only write Q235 or Q345, not Grade A or B, and some do not mention the requirements of friction surface test, nor do they explicitly not make friction test requirements, so the construction unit is at a loss. Some construction units let the design institute recognize the materials after purchasing them, which is a random treatment of the project quality, which is extremely inappropriate.

fourthly, the welding groove form, weld gap, blunt bevel angle, UT grade, single-sided welding, etc. are not indicated in the construction drawing.

In some construction drawings, the splicing welding with different thickness is not inclined according to the specification requirements, and the local stress lines are too concentrated, which violates the national technical specifications, and the quality acceptance often fails, resulting in irreparable defects.

fifthly, the requirements for derusting grade are not indicated in the construction drawing.

There is no requirement for the brand, material and film thickness of paint (coating), so there is no basis for project construction and acceptance.

as a construction unit, after obtaining the construction drawing, we must organize experienced technicians to conduct the blue prints.the design to see if there are any problems with the application specification; Whether the node diagram is clearly stated; Whether the contents required by the mandatory provisions are shown in the general design description, and whether the specifications, models, performances, grades, construction quality requirements and safety grades of various materials are clear; Whether the node design is reasonable; Whether there are insurmountable difficulties in the construction, etc., should be put forward to the design unit in advance. The perfection of design drawings is a prerequisite to ensure the construction quality.

Second, the production quality of steel structure does not meet the requirements

First, when cutting and blanking, the flange plates are different in size, resulting in the inconsistency between the H-beam and the bracket, and the upper and lower flange plates of the steel beam connected with the bracket are staggered by about one plate thickness; There are deep cuts on the cutting edge, obvious depressions on the edge of the board, or deep sawtooth marks, the cutting roughness exceeds the standard, the edge of the mosaic is not vertical, and the splicing is wrong.

second, when assembling, H-beam is welded without assembling jig, which leads to deviation in height and dimension of H-beam and eccentricity of web; After the wing web is butted, the weld is not leveled, and there are obvious bumps; The light steel web is uneven and has not been corrected before assembly.

thirdly, in welding, the wing plate of H-beam welded by light steel is spliced after cutting, and the arc quenching plate is not installed in the weld, resulting in incomplete weld, incomplete fusion of pits on the edge, etc., which is not flush with the base material; The weld leg size of column foot and bracket is smaller than the design drawing, and the fillet weld has serious edge collapse, and the arc closing position is generally lower than the base metal, with more pores; The weld formed by CO2 welding is poor, the width is inconsistent, the height is inconsistent, and it is big and small. Manual welding seam is not straight, the width is different, and the phenomenon of undercut is serious; The spatter of welding slag is not cleaned up.

fourthly, in the aspect of drilling, the drawings were not well checked beforehand, and double rows of holes were opened at the place where the holes were ordered, and the results were left on the component without filling the holes. For example, the H-beam at the joint of column and bracket is double-row hole, while the H-beam with the same specifications as the secondary beam is single-row hole, but double-row holes are opened when opening, which affects the strength and appearance quality after installation.

fifth, in the final assembly process, the joint between the steel column bracket and the H-beam was dislocated up and down, left and right, and the size was not well controlled.

sixth, rust removal and painting: the rust removal is sloppy, and the paint does not meet the grade requirements, and the paint will rust and peel off soon; The thickness of the paint film is uneven, and the thickness of the positive surface is generally super-thick, reaching 25μ m, but the negative surface is often around 9μm (the indoor paint film thickness is set at 125μ m); Before painting, impurities are not cleaned, and there are many dirt, uneven and sagging.

Seventh, during the transportation and stacking of components, there is no flat stacking of shelved parts, but the components are unloaded at will, piled up in disorder, and even buried in the mud ditch, resulting in deformation, collision and pollution of components.

Eighth, when the components leave the factory, the center lines of steel columns and beams are marked.