Sandblasting is a technological process by which a high hardness blasting agent is designed with very high speed on a surface to be removed from the adherent deposits and oxides. In addition, blasting applied to metal coating, to ensure a certain roughness of the surface that helps to anchor the metal particles are deposited on metal.
Investigating the possibility of using sandblasting the operation to increase the roughness of the surface to be metallized have explained the process of sanding to make themselves understood and to establish its limits and possibilities.
Analysis of the blast
To explain the process we feel that blasting is used as castings small shot blasting granulation 0.8-1 mm. The energy contained in a single particle of the jet blast is small, but because it is applied to a very small area, we see that its action is very strong. If we look at a particle blasting agent φ 0.8 mm x 2 weighing 10.3 g and given design speed, which is about 70 m / sec. can determine its kinetic energy.
E = m.v2 / 2 where: m = 2 x 10-3 / 9.81 = 2 x 10-4 g x s2 / m = s2 x 2 x 10.7 kg / m ; v = 70 m / s ; E = 2 x 10-7 x 702 / 2 = 4.9 x 10-4 kg. m
To estimate the area that does this energy have been experiences resulting fingerprints that were measured area. Thus was obtained a surface with an average of 0.0025 mm2 which could correspond to a 0.05 mm square. The measurements made indicate the size of roughness and thus the depth of such fingerprints to a value of about 0.035 mm. Arguably, click on a particle surface with an average of 0.0025 mm2 which deforms to a depth of 0.035 mm, which represents work done by a pellet blasting agent in action.
Apart from the kinetic energy transformed into heat during the impact, can equal the work done with the initial energy:P xd = E, where P is the force that hits the surface, d is the distance that the force acting to produce mechanical work (strain depth)Hence the power P hitting area considered P = E / d = 4.9 x 10-4 / 35 x 10-6 = 14 kgf. Knowing the strength and surface acting, can cause crushing stress: σ = P / S = 14 / 0.0025 = 5600 kgf/cm2 From the foregoing it is apparent that the crushing stress produced by a particle blasting agent in the action is higher even crushing steel unit effort. Under these efforts locally uniform plastic material deforms, causing detachment adherent deposits and oxides on the surface subjected to the action of blasting agent.
From the above it is found that the blast occurred and local plastic deformation of the basic material and removing adherent deposits and oxides from it. This makes the blasting can be used both as an operation to increase the roughness of the surface to be metallized as well as cleaning it. In the latter case will be investigated on surface deposits and if it is found that area are also traces of fat or oil will not apply to blasting operation until the removal of such signs.
Granules surface treatment
Corundum Noble
•Field of use: Used to tightening, grinding precious metal surfaces and light, and surface preparation and cleaning stainless materials. Noble corundum contains ferrite, is steel.
•Size: 53 to 5600 µm
•Hardness: 2050 Knopp kN/mm2
Brown corundum
•Field of use: Ideal for cleaning materials of steel, the cabin by hand in cubicles or open-air blasting. Composition in brown corundum has small or large quantities of iron oxide and other alloys, the characteristics and durability of it.
•Size: 45 to 2800 µm
•Hardness: 9 Mohs each type
Steel pellets GH, GM, and NG
•Application: granules corners are used in blasting booths, the installation of high capacity sandblasted regular cleaning. You can use both remote dross on the surface of basic materials and refining areas for compressed air systems.
•Dimensions: 0.1 to 1.7 mm
(in fraction 9)
•Hardness: HRc min.60 GH GM 52 to 60 HRc, NG 45 to 52 HRc
Alice Steel Type S
•Field of use: Small shot round steel are used to treat steel materials – different shapes, plates, etc. Cleaning castings, heat treated small shot is appropriate for the operation of hardening.
•Dimensions: 0.2 to 2.4 mm
(in fractions 12)
•Hardness: 40 – 50 HRc at each type
Granules stainless GX and CX
•Field of use: both types are granular stainless steels with Cr and CrNi are recommended for blasting of cast aluminum, cleaning and treatment of copper, bronze and steel noble.
•Dimensions: 0.1 to 2.0 mm
(in fractions 10)
•Hardness: HRc 45 GX, CX 30 HRc
Sand granatit
•Range of use: granatit sand is a very pure pellet, contains ferrite, as such materials are used for cleaning steel, nonferrous metals and noble, and water jet cutting. Granatit sand contains large amounts almandita, whose properties determine the tenacity than sand granatit.
•Dimensions: 0.15 to 1.0 mm
(in fractions of 3)
Glass beads
•Field of use: glass beads are used for fine surface treatment, precision components, obtained with appropriate technologies. Marbles, the fine fraction, with uniform spherical shape, suitable to obtain demanding surfaces. Life is influenced largely by corresponding adjustment of the technology.
•Size: from 0 to 600 µm
•Hardness: 5.5 Mohs
Granules of corn cobs
•Field of use: use in grinding, cleaning by protecting areas: metals, wood products, synthetic fibers, plastics, wall, elements with electrical insulation.
•Dimensions: 0.013 to 4.0 mm
(in fraction 7)
•Hardness: 4.5 Mohs
Plastic granules
•Field of use: plastic granules, in addition to cleaning the surfaces of steel, aluminum, galvanized surfaces, plastics industry, are suitable for remote layer of varnish and dust.
•Dimensions: 0.2 to 1.8 mm
(in fraction 4)
•Hardness: 3.5-4.0 Mohs
by PhD Candidate Eng. Elena Irimie – the Ministry of Finance
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