Abrasive Grade Silicon Carbide – Uses Of

Silicon Carbide Grit

Silicon Carbide Grit & Powder

The main uses for abrasive grade Silicon Carbides (Carborundum) are:

  • anti-slip abrasives
  • sandblasting abrasives
  • bonded abrasives
  • coated abrasives
  • polishing/lapping compounds
  • tumbling media (including lapidary or rock tumbling uses)
  • wire-sawing abrasives
  • sintering
  • filling up ceramic parts

Today, there are many high tech uses for varying grades of Silicon Carbide such as electronics, brake pads, ceramics, LED’s, diodes, transistors, semiconductive research, heating elements, even jewelry.  Gone are the days when Silicon Carbide was known only as an abrasive.

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Silicon Carbide – Interesting Historical Facts

Black Silicon Carbide Abrasive

Silicon Carbide Sandblasting Abrasive

Silicon Carbide (SiC) was the first synthetic abrasive to be produced and also the first to be commercialized.  1891 was the year that silicon carbide production began, and thus revolutionized the abrasive industry as a whole.  Before 1891, almost all abrasives were naturally found such as rocks and minerals.

By 1900 SiC production was at 1,200 metric tons, carrying an estimated value of $263,000.  Mainly used in the lapidary industries, it was a replacement for diamond powder.  At that time, the only other manufactrued abrasive was crushed steel and as a contrast in volume, crushed steel production was only 320 tons, carrying a rather paultry value of ~$50,000.

With exception only given to diamond and garnet, by the year 2000, manufactured abrasives dominated the high end abrasive industries.  Unlike natural abrasives, manufactured abrasives could be tightly controlled, thus ensuring uniform properties like hardness and grit size.  A further benefit was the ability to customize the manufacturing process to meet exact specified needs, based on the end application.  While being more expensive that natural abrasives, their durablity and efficiency made them more cost effective overall.  They are therefore used heavily in the metal finishing, cutting, and polishing fields.

In short, manufactured abrasives are extensively used today in finishing numerous products.

 

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Number One Cause Of Premature Coatings Failure

The most common cause of premature coatings failure is improper ANCHOR PATTERN.

What is anchor pattern?  It is a term used to describe the roughness (etch, or profile) that is created on a surface when sandblasted.  The Anchor Pattern is measured in 1/1000th of an inch, which is called a MIL.  Paint coatings are also measured in MILS as well, making it a term that is easy to remember.

Coatings require specific mils of anchor pattern in order to properly adhere to the surface it is applied to.  Each coating will have different requirements.  Therefore, you cannot simply sandblast a surface clean and then apply paint to it without technical information on what mils profile that particular coating requires (among other factors).  If you simply guess at what profile you need, you risk premature coatings failure.

If you have no access at all to the coating manufacture’s technical data and need to make an educated guess, you will want to consider the following rule of thumb:

The mils of anchor pattern you create on the surface to be coated, should be 25 to 30% of the DRY film thickness of the total coatings system BUT NEVER greater than the dry film thickness of the primer coat unless additional coats are to be applied immediately.

Also key to understand is that the wet mils of a coating will be different than the dry mils of a coating.  Many coatings shrink tremendously, depending on the percentage of solids contained within them.  Make sure that the anchor pattern you create when sandblasting is much shallower than the total coatings when dry.

Other factors that impact the development of anchor pattern include the type of steel you are blasting (including hardness and chemical composition), how the steel was formed, prior use of the steel, the type of abrasive you use to create the anchor pattern (including size, shape, hardness, and velocity), as well as what type of blast nozzle you choose to use and how you use it (such as angle and distance to the work surface).

The chart below is a crude approximation of abrasive size to anchor pattern, and should thus be used only as a starting point only for both centrifugal wheel and pressure blasting.

  • 1 Mil Profile = G80 Steel Grit, 100 Mesh Garnet, S110 Steel Shot, 3060 Coal Slag
  • 1.5 Mil Profile = G50 Steel Grit, 100 Mesh Garnet, S170 Steel Shot, 3060 Coal Slag
  • 2.0 Mil Profile = G40 Steel Grit, 3060 possibly also 80 Mesh Garnet, 36 Grit Aluminum Oxide, 3060 Coal Slag, 3060 Copper Slag
  • 2.5 Mil Profile = G40 Steel Grit, 3060 Mesh Garnet, 24 Grit Aluminum Oxide, 2040 Coal Slag, 2050 Copper Slag
  • 3 – 4 Mil Profiles = G25 Steel Grit, 36 possibly also 3060 Mesh Garnet, 16 Grit Aluminum Oxide, 2050 or 1230 Copper Slag, 1240 Coal Slag

 

 

 

 

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Boron Carbide Blast Nozzles – When To Use One

Short Answer: Use a boron carbide blast nozzle anytime you are using aluminum oxide or silicon carbide as your abrasive blasting media.

When To Use Boron Carbide Blast Nozzles
When To Use Boron Carbide Blast Nozzles

Long Answer:   The three most popular materials used today for blast nozzles are Tungsten Carbide, Boron Carbide, and Silicon Carbide.  Boron Carbide nozzles are the hardest of the three, followed by Silicon Carbide, and then by Tungsten Carbide.  Hardness is necessary to order to withstand the wear and tear that the blast nozzle liner will be exposed to by the abrasive used.

However, the greater the hardness, the more brittle the material.  This is why Boron Carbide nozzles need to be handled with care.  When we ship B4C blast nozzles, we use a lot of packaging material to ensure safe transit.  Never drop, throw, pound, or abuse a boron carbide nozzle or you will destroy it.  (Just because boron carbide is the hardest material you can buy, does not mean it is not brittle.)

 

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Cleaning Bronze with Glass Bead Blasting

Here is a great video and article on glass bead sandblasting.

This company is using a fine glass bead to remove bronze patina from outdoor monuments, which restores them to their original state.  I would have liked to see some before and after photos of the monuments, but the article does contain a video clip where you can see (from a distance) the cleaned and uncleaned areas.

Workers from Sterling-based Mercer Lettering and Monument Works have been  sandblasting and pressure-washing the granite stonework over the past few weeks.  The granite stones also have been treated with an organic acid designed to  preserve the grass below while removing fungi from cracks in the stone.

On Thursday, they aimed nozzles at the bronze plaques and sprayed them with  fine glass particles. That removes the patina, or green and brown film, that has  developed on the metalwork over time without damaging the metal below it, said  Graeme Everson,  the company’s owner and a National Guard veteran.

“It brings back the shine of the bronze as it was when they put it up,” he  said.

The article does not discuss the size of the glass bead used, nor the exact machine they used, but the video shows the actual operator blasting.  You can therefore see the blast pot and the operator’s protective head gear which is useful for those just starting out and not familiar with protective gear.

To see the full original article by By ALISON SHEA of The Bulletin: Jewett City monuments gleam like new – Norwich, CT – The Bulletin http://www.norwichbulletin.com/news/x1474279320/Jewett-City-monuments-gleam-like-new#ixzz21poiW0in

© Copyright (c) ALISON SHEA The  Bulletin Originally Posted May 18, 2012

 

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Venturi Sandblast Nozzles Vs Straight Bore Blast Nozzles

Schematic Drawing of a Venturi Nozzle

So what is the real difference between these two types of nozzles, and why should you care?  Well, for starters, you should know that the introduction of venturi nozzles over thrity years ago still remains the last major advance in nozzle technology.  Thirty years is a long time!

You see up until the mid 1950’s, all sandblasting nozzles were straight bore.  They had a tapered converging entry, a parallel throat section, and a full length straight bore and straight exit.  Over time, blast operators noticed that as the interior of these nozzles began to wear and erode away, a larger and more efficient blast pattern resulted.  This observation led to the development of the venturi design.

A long venturi nozzle is characterized by having a long tapered converging entry, with a short flat straight section, followed by a long diverging end which widens as you reach the exit end of the nozzle.  A long converging entry introduces the air and abrasive mix into the nozzle, then is constricted into a short flat straight section, and then forced out the flared exit end.  Venturi nozzles can increase productivity by as much as 70% due to the larger abrasive pattern that results as well as due to the increase in velocity of the abrasive as it exits the nozzle.  In fact, velocity (outlet speed) of the exiting abrasive can be nearly double that of a straight bore nozzle, and this is force that cleans a surface faster!

So if you are in the market looking to upgrade your operation, perhaps changing to a venturi nozzle might be a good place to start.  More on that later…

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Garnet Abrasive Mil Profiles (Anchor Pattern)

Sizing and Profile Information:  (!)  NOTES:  Anchor patterns will vary tremendously based on other variables such as hardness & type of steel, level of corrosion being removed, blast angle, blast distance from the steel, etc.

  • 36 – Coarse.   Produces a 3.5 – 4.5 mil profile on steel surfaces.  Generally used for thick coatings, marine fouling, and rust.
  • 30×40 – Intermediate.  Produces a  2.5 – 4.0 mil profile on steel surfaces.  Used on heavier coatings up to 40 mils, and rust.
  • 30×60 Medium.  Produces a 2.0 – 3.5 mil profile on steel surfaces.  Considered to be an overall workhorse grade for new steel and maintenance for coatings up to 20 mils.
  • 80 Mesh – Medium Fine.  Produces a 2.0 – 3.0 mil profile on steel surfaces.  Great for aluminum and other sensitive substrates.
  • 100 Mesh – Fine.  Produces a 1.0 – 2.5 mil profile on steel surfaces.  Also can be used on aluminum and fiberglass, as well as for rust removal and mill scale on new steel.

Garnet is a industrial gemstone sandblasting abrasive  that creates a profile virtually free of embedment, which makes it excellent for coating adhesion, as well as applications where low or no transfer of grit into the substrate can be tolerated.  Clean and Fast!

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Mil Profile Chart for Brown Aluminum Oxide

Aluminum Oxide Grit

Sandblast Grit - aluminum oxide

Mil Profile Chart for Aluminum Oxides – These Are Approximations Only!  Approximations are based on using a pressure blaster on hot rolled steel, having tightly adhering mill scale, using a 90-100 psi.  Anchor patterns will vary tremendously based on other variables such as hardness & type of steel, level of corrosion being removed, blast angle, blast distance from the steel, etc.

These mil profiles are for Brown Fused Aluminum Oxides, including Sinterblast.

1 mil profile = 100 grit aluminum oxide
1.5 mil profile = 50 grit aluminum oxide
2 mil profile = 36 grit aluminum oxide
2.5 mil profile = 24 grit aluminum oxide
3 mil profile = 16 grit aluminum oxide
4 mil profile = 12 or 16 grit aluminum oxide

Aluminum oxide is a very hard, tough, durable abasive that can be recycled many times.  It is also expensive, so you should only use it in a blast cabinet or blast room where it can be recycled and reused many times.  Recommended by OSHA as a replacement media for silica sand.

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Do It Your Self Sandblasting

Here is a fantasic business in Vancouver, B.C. that a couple of entrepenurs started recently. Do-it-yourself sandblasting! Now why didn’t I think of that?  Don’t we all have old furniture, rusted equipment, & gardening supplies that could use a facelift?

Everything from vintage metal toys and wooden chairs to bathroom tiles and car parts are being scoured clean at a Victoria do-it-yourself sandblasting company.

Customers pay $1 per minute (minimum 15 minutes) to blast their items, or $1.35 per minute (minimum 20 minutes) for a staffer to do the work at Blast It!, located in the Hillside industrial area at 2639 Turner St.

It’s easy. An item is placed inside a self-contained cabinet. Once the door is locked, a customer standing outside the cabinet slips his or her hands into heavy duty gloves which run into the interior. Turn on the control with your foot, point the nozzle of the wand at the item and the blasting starts. Continue reading

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Sandblasting Media: Welcome to SandblastingAbrasives.com!

Offering a FULL line of sandblasting media, powders, and blast nozzles.

Silicon Carbide Grits 12 and 30 ANSI

Silicon Carbide Sandblasting Media

Having trouble finding a triple graded, Boron Carbide Sapphire Polishing Powder?  Or a very coarse Brown Fused Aluminum Oxide for anti-skid applications?  We offer the full line of ANSI & FEPA sandblasting media and powders, not just the most popular sizes!

Now offering a full line of Made-In-The-USA Sandblasting Nozzles, in both Boron Carbide and Tunsten Carbide.

If your order is 200 lbs or less, we encourage you to simply order online.  For orders over 200 lbs, please use our Request A Quote form, so we can provide a custom freight quote as well as wholesale pricing.

Most of our abrasives can be ordered online in small quantities, or ordered offline via a wholesale account.

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