H빔 쇼트블라스트 전 준비방법 : 원자재 상태부터 코팅 요구사항까지

Surface preparation targets from subsequent coatings

shot blasting uses abrasive impact to remove rust and oxide scale within the applicable range and form a surface profile to create conditions for subsequent painting. What results need to be delivered should be determined by the project specifications, coating system and usage environment, not automatically by the shot blasting machine model.

Cleanliness, roughness and residual contamination are different requirements. A gray surface that appears uniform may still contain dust, salts or inappropriate contours. The plan should separately describe the objectives, inspection methods, sampling locations and failure treatment to avoid using a surface photo instead of a complete acceptance.

Incoming materials are grouped first to identify situations that require preprocessing

Beams of the same cross-section may require different preparation procedures if they have different corrosion, scale, old coatings, oil stains or welding residues. Select representative parts according to the actual incoming material status, not just the new material adjustment machine that is easiest to clean.

Cleanliness and roughness are determined separately

When a project adopts visual cleanliness standards such as ISO 8501-1, the applicable levels and comparison methods should be stated. The surface profile is evaluated according to the coating requirements according to agreed methods, e.g. using the corresponding ISO 8503 method. The website does not set a certain grade or fixed micron value as the default standard for all parts.

For dust, soluble salt and other required items, separate inspection items and limits need to be set. Abrasives, incoming materials and storage and transportation may affect the results, so the inspection after shot blasting should be connected with the re-inspection before painting.

Use representative cross-sections to test true coverage

The inside of the flange of the H-beam, both sides of the web and the root of the weld need to be checked in conjunction with the placement direction; the connecting plate, end plate and stiffener may also form obstructions. The fact that the opening is large enough only indicates the passing conditions, but does not prove that the same cleaning effect can be obtained in all locations.

The test run should record the workpiece cross-section and attachments, loading direction, abrasive status, blast wheel configuration, conveying conditions and inspection results. Difficult-to-treat locations should be clearly marked on the inspection chart; after discovering the shadow area, first check the coverage and loading, and then decide whether to adjust the process or add supplementary processing.

Hand over the processing results to the next process

After shot blasting, the remaining pellets and floating dust at the agreed location should be cleaned up, checked to see if the requirements are met, and the identity and release status of the workpiece should be maintained. Parts that have been inspected, parts to be inspected, and parts for repair cannot be automatically entered into spraying just because the equipment has finished running.

Storage, transfer, and waiting times can alter surface conditions. The coating interval, temperature and humidity, steel temperature and dew point relationship should be implemented according to the project and coating technical documents; a general number of hours should not be used to cover all workshops.

Inquiry and trial operation preparation list

• Provide coating system or surface treatment specifications that list cleanliness, roughness, and contaminant requirements respectively.
• Use photos and samples to illustrate actual rust, old coatings, oil stains and welding residues.
• Mark all surfaces and areas to be cleaned and protected.
• Clarify the blocking position, loading direction, number of representative parts and inspection methods.
• Confirm who is responsible for pretreatment, shot blasting, inspection, transit protection and coating review.