Technical requirements for surface blasting process
1 is carried out according to the specifications of SDZ01.1, using sandblasting and rust removal;
2 The surface of the treated steel shall meet the descaling grade Sa2.5 specified in GB8923, and the roughness shall be in the range of RZ60um~80um;
3 Paint painting is carried out within 12 hours after the surface pretreatment is completed.
Spotting construction points
Process parameters
1 abrasive material chooses cast iron sand with a particle size of 0.5mm~1.5mm. Abrasives are required to be angular, clean, dry, and free of oil;
2 injection treatment of all compressed air through the cooling device and oil water separator to ensure that the compressed air is dry, oil-free, compressed air pressure is 0.7MPa;
3 nozzle to the base metal surface to maintain a distance of 100mm~300mm;
4 nozzle orifice diameter increases due to wear, need to be replaced when its diameter increases by 25%;
5 The angle between the spray direction and the normal of the base metal surface is controlled at 15~30. Within the scope.
Quality Assessment
1 Surface blasting treatment Cleanliness and surface roughness shall be evaluated under good scatter daylight or artificial conditions with comparable illuminance;
2 When assessing the surface cleanliness level, the metal surface of the tested substrate is visually compared with the corresponding photo in GB8923 “Corrosion grade and rust removal grade of steel surface before painting”. The Sa2.5 standard is that the surface of the steel is treated very thoroughly, that is, there are no visible deposits of grease, dirt, scale, rust and paint coating on the surface, and slight spots such as dots or stripes are seen.
3 When assessing the surface roughness, compare the roughness grade with the standard sample according to GB/T13288 “Evaluation of the surface roughness grade of the steel before painting (Comparative Sample Method)”, or directly measure the surface roughness value with the instrument. .
Operation points
1 The blasting equipment should be as close as possible to the work to reduce the length and pressure loss of the pipeline, avoid excessive pipe wear, and facilitate the construction personnel to contact each other;
2 sandblasting hoses strive to be straight, reduce pressure loss and concentrated wear of the hose to the hose. For the places that must be bent during construction, the direction should be changed frequently to make the wear even and extend the service life of the hose;
3 In order to prevent leakage and emptying, reduce the number of shifts, improve the utilization rate of abrasives and work efficiency, comprehensive consideration should be made before construction, the injection position should be reasonably arranged, and the injection route should be drawn up;
4 Depending on the air pressure, sand output and structural surface contamination, the nozzle movement speed can be flexibly controlled;
5 During the spraying process, the gas-to-gas ratio is adjusted in time according to the air pressure, the nozzle diameter, the rust state of the structure surface, the quality of the treatment, and the efficiency;
6 After surface pretreatment, use dry, oil-free compressed air to remove floating dust and debris. The surface after cleaning shall not be touched by hand;
7 If the surface of the base metal is found to be contaminated or rusted before painting, it must be reprocessed;
8 Pre-treatment After completion of the inspection, it is necessary to spray as soon as possible, and the shorter the interval, the better. In environmental conditions such as humidity or industrial atmospheric pressure, it must be painted within 4 hours. When the weather is not sunny or the temperature is not high, the longest interval should not exceed 12 hours.
Working conditions for sandblasting on steel surfaces
1 air relative humidity is less than 85%;
2 The surface temperature of the base metal is at least higher than the dew point 3. C;
3 Before the blasting treatment, carefully remove the deposits such as welding slag and splash, and clean the grease and other contaminants visible on the surface of the base metal.
