Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
sand blast 3
- Thread starter ehsanhzh
- Start date
-
2
- #2
racookpe1978
Nuclear
Are you specifying the material to be blasted (specifying the quality of the copper slag), or are you concerned about the material being blasted BY the copper slag - and need to know the variables IN the different copper slags that might be used, or are you trying to evaluate different blast materials - and need to find out if the"average" copper slag available is the right material to be used?
Regardless. What specifications are YOU going to impose on YOUR supplier of the copper slag, and how important will be variations in the copper slab he provides, and how much are YOU willing to pay to control quality of the different copper slag he uses (and re-uses?) every shift ?
Regardless. What specifications are YOU going to impose on YOUR supplier of the copper slag, and how important will be variations in the copper slab he provides, and how much are YOU willing to pay to control quality of the different copper slag he uses (and re-uses?) every shift ?
- Thread starter
- #3
-
1
- #4
I don't believe that there is any significant relationship between hardness and density. A Materials hardness is related to its tensile strength. I do not know much about copper alloys or abrasive slags, but I believe the above statements are true in the general case. I will put forward steel as an example of why I thank that is true.
Material hardness in steels can vary widely in the same chemical composition of material based solely on heat treatment. Minute changes in chemical composition can also have a large affect on maximum material hardness with a minimal change in density. Most steels are almost identical in density due to the major iron content. I assume a similar situation exists with copper alloys.
As side not racookpe what factors would one want to look out for in specifying for an abrasive slag, and how would one test and ensure that level of quality/consistency? Particle size? Content of other materials?
Material hardness in steels can vary widely in the same chemical composition of material based solely on heat treatment. Minute changes in chemical composition can also have a large affect on maximum material hardness with a minimal change in density. Most steels are almost identical in density due to the major iron content. I assume a similar situation exists with copper alloys.
As side not racookpe what factors would one want to look out for in specifying for an abrasive slag, and how would one test and ensure that level of quality/consistency? Particle size? Content of other materials?
racookpe1978
Nuclear
Abrasive blasting is a bit more complex than obvious. And often, its more complex than "sandblast" - but it doesn't have to be.
What IS ABSOLUTELY critical is what the final finished surface has to be (cleanliness, smoothness, evenness of finish, roughness of surface, flatness (contour) of surface -> (no erosion of flat areas into pits and gouges, no removal of cast or machined "outcropping" by over-enthusiastic blasting), degree of embedded grit left in the surface, amount of original "crud" left in the nooks and crannies in the surface.
If the abrasive grit is recycled - and it often is! - how much "crud and grit" from previous cycles are acceptable? For example, if you are blasting stainless steel or an alloy, can you allow recycled grit from a previous carbon steel part to be used? Probably not! Can you allow old paint or rust or crud from a previous cycle be blasted back onto this project? Maybe. Maybe not.
If you allow nut (shells) to be used so you don't scar the surface, how much "dust" can you afford in your tank? Maybe dust control is more important "time to blast"? Maybe "time to blast" is more important, and the sandblast crew will be wearing full air-fed hoods anyway, but need special heating or cooling safety gear.
How you get that final surface is sometimes less important than what the crew uses. Both usually work together - Get a specific capability and recommendation from the various venders who will be doing the blasting! Some companies are set up for walnut shell blasting, others use industrial grits of various hardness and "sharpness" because they can control the grit size and sharpness.
See, you have asked about hardness only. But grit "shape" - the actual pointy tips of each piece of blast material is what does the cutting at the microscopic level. As grit wears away, it becomes more and more rounded and less effective in cutting the particles on the surface. More rounded grit hitting a surface for longer periods of time begins to blast the surface "crud' INTO the metal, not cutting it OFF OF the metal which is what you want.
A piec of sandpaper wears three ways: The individual grit becomes rounded and not effective; the individual grit gets worn off of the sandpaper entirely and the paper becomes smooth; and the paper builds up with eroded grit, the paint or wood or plastic that been worn off, and the worn off grit tips and edges and so does not even touch ort cut the surface anymore. Same thing happens with balst grit.
What tables have you looked up for sandblast mediums?
What IS ABSOLUTELY critical is what the final finished surface has to be (cleanliness, smoothness, evenness of finish, roughness of surface, flatness (contour) of surface -> (no erosion of flat areas into pits and gouges, no removal of cast or machined "outcropping" by over-enthusiastic blasting), degree of embedded grit left in the surface, amount of original "crud" left in the nooks and crannies in the surface.
If the abrasive grit is recycled - and it often is! - how much "crud and grit" from previous cycles are acceptable? For example, if you are blasting stainless steel or an alloy, can you allow recycled grit from a previous carbon steel part to be used? Probably not! Can you allow old paint or rust or crud from a previous cycle be blasted back onto this project? Maybe. Maybe not.
If you allow nut (shells) to be used so you don't scar the surface, how much "dust" can you afford in your tank? Maybe dust control is more important "time to blast"? Maybe "time to blast" is more important, and the sandblast crew will be wearing full air-fed hoods anyway, but need special heating or cooling safety gear.
How you get that final surface is sometimes less important than what the crew uses. Both usually work together - Get a specific capability and recommendation from the various venders who will be doing the blasting! Some companies are set up for walnut shell blasting, others use industrial grits of various hardness and "sharpness" because they can control the grit size and sharpness.
See, you have asked about hardness only. But grit "shape" - the actual pointy tips of each piece of blast material is what does the cutting at the microscopic level. As grit wears away, it becomes more and more rounded and less effective in cutting the particles on the surface. More rounded grit hitting a surface for longer periods of time begins to blast the surface "crud' INTO the metal, not cutting it OFF OF the metal which is what you want.
A piec of sandpaper wears three ways: The individual grit becomes rounded and not effective; the individual grit gets worn off of the sandpaper entirely and the paper becomes smooth; and the paper builds up with eroded grit, the paint or wood or plastic that been worn off, and the worn off grit tips and edges and so does not even touch ort cut the surface anymore. Same thing happens with balst grit.
What tables have you looked up for sandblast mediums?
Ehsanhzh:
I would be more concerned about the condition of the finished product, after blasting. The removal of all rust or other foreign matter, etc., to bare metal (or whatever final condition), the roughness of the blasted surface as this relates to final finishing processes, and that the blasting process not leave any impingement residue on the surface which might be detrimental to the finished product. Otherwise, what you seem to be asking is mostly the concern of the blasting equipment/system and medium supplier. They should be able to discuss your issues with you. I suspect slag is kinda glass-like in hardness, brittleness, sharpness, cutting ability, etc. It’s a byproduct of another process which is turned to another useful purpose, rather than just being a disposal headache, at the copper smelting plant.
I would be more concerned about the condition of the finished product, after blasting. The removal of all rust or other foreign matter, etc., to bare metal (or whatever final condition), the roughness of the blasted surface as this relates to final finishing processes, and that the blasting process not leave any impingement residue on the surface which might be detrimental to the finished product. Otherwise, what you seem to be asking is mostly the concern of the blasting equipment/system and medium supplier. They should be able to discuss your issues with you. I suspect slag is kinda glass-like in hardness, brittleness, sharpness, cutting ability, etc. It’s a byproduct of another process which is turned to another useful purpose, rather than just being a disposal headache, at the copper smelting plant.
- Thread starter
- #7
- Status