Treatment And Application Of Brown Corundum On Stainless Steel Surface
Stainless steel surface treatment and abrasive requirements
1. No casting steel surface treatment requirements
(1) Surface cleanliness P1, surface cleaning grade Sa2.5 (2) roughness between 40-75p m, soluble salt S 30mg/m2(equivalent to NaC1) (3) Relative humidity <60%, stainless steel surface temperature at least 5℃ above the dew point temperature
2. No casting steel punching abrasive requirements
(1) Abrasive clean, hard, angular (2) PH test paper PH, dry and conductivity <1505s/cm (IS011127-6) (3) abrasive quality should be approved by the shipowner and paint manufacturer
Introduction and comparison of technical indexes of garnet and brown corundum abrasive
1. Garnet and brown corundum abrasive introduction
(1) garnet abrasive
Garnet is a natural ore processing from the abrasive, to iron and aluminum garnet (mainly iron-containing aluminum silicate crystals), hardness generally does not exceed 8 Mohs, manufacturers generally have large garnet mines, the main producing area in Shandong, Jiangsu, Inner Mongolia.
(2) Brown corundum abrasive
Brown corundum is made of bauxite and auxiliary materials smelted at a high temperature above 2,000℃ in an electric arc furnace. The hardness of a grade is usually greater than 9 Mohs, and the alumina content is more than 96%. The main producing areas in Henan, Guizhou and other regions.
Sand-washing experiment of garnet and brown corundum abrassives
Experimental equipment and methods: Environmental protection automatic sand washing machine, 12mm secondary air inlet nozzle, roughness tester, 600mm*800mm stainless steel plate 6 pieces, garnet and brown corundum abrasive 500kg each; Garnet abrasives commonly used in domestic shipyards and brown corundum abrasives of different specifications were used for experimental comparison, as shown in Table 2 and Table 3 respectively.
Experimental results in Table 3 show that:
(1) As the particle size of brown corundum abrasive decreases, the surface roughness of stainless steel also decreases, but the surface cleanliness of stainless steel gradually increases.
(2) The selection of first-class brown corundum and high-quality iron and aluminum garnet abrasive indicators can meet the requirements of the technical specifications.
(3) Compared with brown corundum, garnet has a congenital lack of hardness, so it is not as good as brown corundum abrasive in terms of sand punching efficiency and damage rate.
(4) There is a common problem of sanding in garnet punching sand, although the selection of small-particle abrasive can solve the sanding, the roughness out is difficult to meet the requirements of 40-75um, and the 22-mesh grain size of brown corundum abrasive can meet the roughness requirements.
(5) The surface of garnet after sand washing is more bright and beautiful, and it is more acceptable in cleanliness.
(6) The dust produced by both sand washing is very large, in comparison, garnet dust is more harmful to occupational health.
conclusion
Considering the factors such as cost control, technical requirements and punching efficiency, brown corundum abrasive is more suitable for the application of stainless steel surface treatment in the ballast tank of chemical tanker.
