2.
Generally speaking, the components entering the site, whether primary or secondary welds, shall be subject to nondestructive testing of internal defects, and the testing method and quantity shall meet the requirements of article 5.2.4 of gb50205-2020.
The author puts forward the following points for quality control according to his own on-site experience.
This article must be strictly observed.
At present, the vast majority of steel structure surface rust removal adopts “sand blasting rust removal” to remove the rust on the surface.
According to the market situation, the galvanizing amount of such components is generally difficult to reach its claimed thickness and grams.
Note: This article is a work semi summary article.
Figure 2: the paint layer falls off due to incomplete derusting.
1、 Generally speaking, the processing of steel structures is completed in professional factories.
After the rust removal of steel structure members, it is best to send personnel to the site for acceptance to make them meet the specified standards before spraying paint.
Weld flaw detection shall be carried out according to the requirements of the design drawings.
Therefore, the quality requirements shall be clarified with the manufacturer when the contract is re established.
The corresponding mobilized steel materials shall be sampled and re tested.
The allowable deviation of paint film thickness shall be 25 um.
The thickness of the paint directly determines the durability of steel.
If the construction quality is not assured, the primer and finish paint of different colors can be selected for painting, which can be easily distinguished at that time.
In addition to testing the above data, the galvanizing amount should also be approved.
To solve this problem, it is necessary to require the project manager or material manager to plan in advance.
1.
Purlins, pull rods and support pipes can be called secondary components, which are generally hot-dip galvanized components.
Article 5.2.4 specified in the specification is mandatory and must be strictly implemented, which is related to welding quality and structural safety.
The second is to share their own summary in construction, so as to provide reference for those who have not participated in steel structure construction practice.
Paint thickness inspection.
One is to clarify his own ideas and summarize himself through his own writing.
The first part is foundation construction; The second part is the construction of main steel frame; The third part is the construction of fire retardant coating; The fourth part is the construction of profiled steel plate; The fifth part is maintenance and repair.
Because incomplete rust removal will seriously affect the durability of steel structure, the problems caused by incomplete rust removal are often difficult to appear in the initial stage.
According to the situation of the project site, the rust of components often starts from these places, which are difficult to find in ordinary days.
4.
If the high-strength bolt design adopts friction bolts, the torsion of the steel beam will lead to the torsion of the bolts, which will directly affect the stress of the structure.
I hope you will give me your advice.
When receiving the goods, the shipping manufacturer shall be required to pack and classify them, so that the quantity can be checked at that time.
After the components are processed, they are transported to the installation site by land or water, and then installed.
If it is impossible to detect before spraying paint, the component surface needs to be polished, because coupling agent is required during flaw detection, and the paint will hinder the transmission of signal.
The reason for this result is often that the steel can not be mobilized in advance and the arrangement of inspection and experiment plan is not paid attention to.
The content in it is summarized by the author through his own practice.
Figure 1: weld flaw detection 3.
When it is found that the specifications of goods do not meet the contract or design requirements, they shall be rejected.
The quantity, geometric dimensions and specifications of these components shall be checked when entering the site.
The geometric dimensions of components shall be checked with steel ruler or vernier caliper for their length, thickness and diameter.
In many cases, the “processing while inspection” can not be “used after passing the inspection”.
Such quality problems are often difficult to find.
According to the requirements of specification 13.2.3 (strong article), the paint thickness must meet the design requirements.
4.
Figure 3: paint thickness detected by paint film tester During the inspection of paint thickness, not only the “front” shall be inspected, but also the edges, corners, corners and other weak places that are difficult to spray.
Steel sampling and re inspection shall be carried out according to the provisions of article 4.2.1, 4.3.1, 4.4.1 and 4.5.1 of gb50205-2020 standard for acceptance of construction quality of steel structures.
This time, through his own sharing, he aims to achieve two purposes.
Rust removal and painting of components has always been an unavoidable disadvantage of the steel structure itself.
The key to painting is the treatment degree of steel base layer in addition to the quality of paint itself and the operation level of workers.
Re inspection is not only the quality control of steel structure components, but also the necessary process of forming engineering data.
Therefore, it is necessary to spot check the galvanizing amount..
At present, the most common and common method for rust prevention of steel structure is painting.
Therefore, most manufacturers will steal work and materials in this step, and they may survive once or twice as required by the specifications and drawings.
When it is found, it is often very rusty, Therefore, prior control is particularly important.
Therefore, when the steel structure enters the site, it is necessary to check its geometric dimension and Steel Structure Deepening drawings, and its error meets the specification requirements, especially the position deviation of bolt holes of components, which will directly affect the installation accuracy, For example, if the bolt hole position deviation of the two girders is too large, the girder splicing will not be aligned.
Sand blasting rust removal refers to the use of air compressor to spray high hardness sand such as quartz sand, Emery and iron sand onto the steel surface, and use high kinetic energy to form small grooves on the steel surface, so as to achieve the purpose of rust removal.
Raw materials can be processed only after they pass the re inspection.
There must be no concession here! On the other hand, the cost of paint accounts for an important part in the whole steel structure processing process, which is not only reflected in the expensive price of paint, but also reflected in the labor cost of paint, allocation of paint equipment, secondary handling, occupation of site and other expenses.
With the passage of time, the surface will often rust again after several years, and even more serious peeling may occur, Therefore, on-site supervision is very necessary.
These components are often in large quantities.
Steel structure members need to be accepted when entering the site, and the acceptance can be inspected according to appendix h of gb50205-2020 standard for acceptance of construction quality of steel structures (hereinafter referred to as the code).
Weld flaw detection is best carried out after welding and before spraying paint.
5.
As my experience is reduced, there must be something wrong with the contents or practices mentioned in it.
This paper is divided into five parts.
Most components of geometric steel structure need to be cut and welded, and welding often causes deformation.
According to the specification, design and painting requirements, the derusting grade of steel structure surface shall reach the corresponding grade, and the derusting surface of steel structure shall meet the specification steel surface treatment before coating – Visual assessment of surface cleanliness – Part 1: rust grade and treatment grade of uncoated steel surface and steel surface after overall removal of original coating GB / t8923.1 Corresponding picture level in the.
Generally speaking, the mobilization materials of steel structures should be strictly sampled according to the items and sampling frequency specified in the specifications, but the actual situation is often unsatisfactory.
During inspection, use dry paint film thickness gauge to check.
Criminals will make a fuss here and shoddy them.
When there are no design requirements, the total thickness of dry paint film of the coating shall not be less than 150um outdoors and 125um indoors.
During the re test, the “inspection of yield strength, tensile strength, elongation and thickness deviation” shall be carried out, and the sampling must be witnessed.
Each component is tested at 5 places, and the value of each place is the average of the coating dry paint film thickness of 3 measuring points 50mm apart.
If it is found to be unqualified, it shall be returned to the factory for re spraying until it is qualified.
Another advantage of flaw detection before painting is that if unqualified components are found, repair welding can be carried out in time.
