What is shot blasting used for? In this guide, we explain what shot blasting is, how it works, and more. Discover the ins and outs of this versatile surface preparation technique and learn how it is utilized across various industries. Whether you're a professional in construction, manufacturing, or restoration, understanding what shot blasting is and its applications is crucial.
What is Shot Blasting?
Shot blasting is a mechanical cleaning procedure that removes oxides and other impurities from a different material's surface. It's a member of the abrasive blasting techniques family, which includes sandblasting.
The main difference is that sandblasting propels sand grains using compressed air, while shot blasting employs spherical shots propelled by a centrifugal wheel. This makes shot blasting a more controlled process. Both techniques serve to clean, modify and improve materials but are used depending on the task at hand.
How Does Shot Blasting Work?
Shot blasting is a cleaning and polishing process that involves blasting spherical materials, known as shot media, at a surface. The choice of shot media is critical to the process, and this depends on the type of material being cleaned. The effectiveness of the operation depends on various factors including the size, hardness, and type of material being cleaned.
This also shapes the amount of material that needs to be removed. The material that the surface is made from also influences the size and type of shots that should be used. The motion and speed of the shot are also vital parts of the process.
Centrifugal wheels, popularly used as the propulsion method, throw the shot media. The shot-blasting media is placed into a centrifugal wheel, which accelerates it to the necessary speed before it's fired into the shot-blasting gun.
The operator or machine then manages the flow of shot media to clean the surface efficiently. Many shot-blasting machines are equipped with a recovery system, to recollect and reuse the shots fired against the material. This system harnesses a vacuum cleaner as the standard method for shot blast recuperation.
What Does The Term “Blast Media” Mean?
The term "media" refers to the type of abrasive material used in the shot-blasting process, a common practice in surface treatment and cleaning.
Key attributes of the abrasive include the grade, denoting the size of the media; the shape which can be either spherical or angular; its hardness, gauged according to the Mohs scale; and its mineral composition.
Each of these characteristics influences the resulting appearance of the treated surface. Understanding these elements is vital when choosing the right media for a specific shot-blasting task.
Benefits Of Shot Blasting
Shot blasting is a surface treatment process slightly different from sandblasting, as it doesn't necessitate the use of sand. The process involves bombarding a surface with steel pellets to rid it of debris and stains, proving incredibly efficient at eliminating corrosion.
Corrosion can be a major issue, particularly for metals, as it can trap moisture beneath the surface. This escalated moisture can apply pressure against the metal, leading to more severe damage. This corrosion may emanate from a variety of sources, such as rust or mill scale.
A highly versatile process, shot blasting can be employed on numerous kinds of metals and boasts the ability to remove even highly rusted metal surfaces. Notably, it performs this function without employing potentially harmful chemicals or acidic substances. Rather, it utilises small steel pellets, which physically scrape away the contaminants on the surface.
By eliminating corrosion, shot blasting helps release the trapped moisture and subsequently allows the preservation of the metal. The process can also flatten surfaces. If a flaw has been discovered, the shot blasting machine can be directed toward that specific area to level it out, ensuring the defect doesn't extend deeper than it initially appears.
This strategy not only provides cleaner results but is also time-efficient compared to standard cleaning methods, making it cost-effective in the long run. This has led to its growing popularity in multiple industries, with a consistent increase in its uptake predicted. Another major advantage of shot blasting is the reusability of the steel pellets, making the process sustainable as well as effective.
Types Of Blasting:
Grit Blasting
Grit blasting, a technique often used for either cleaning a hard surface or creating a profile on it, centres around the use of angular or sub-angular particles. This trait gives the process its distinctive name of "grit" blasting. While it shares similarities with the effects of sandpaper, grit blasting manages to polish surfaces more swiftly and evenly.
The main process entails the removal of dirt from the surface of an object by engaging it with a high-velocity jet of some abrasive substance. This is familiar to many in the form of "sandblasting". This specific method uses a potent spray of sand particles to remove substances like grime and corrosion from surfaces comprised of materials such as concrete.
While there are instances when wet blasting is employed, the most common procedure involves a typically dry stream that is pushed out through compressed air. Importantly, it's worth noting that the abrasiveness level of grit blasting situates itself midway between shot and soda blasting. This makes it a versatile tool for a variety of cleaning tasks.
Wet Blasting
Wet blasting, also known as vapour blasting, is often chosen for outdoor and marine jobs as it reduces dust. The process involves using water, which can make areas cleaner and safer by controlling the abrasive. It also saves time and money as there's less cleaning up to do after.
For some tasks, it can also be done in a controlled environment, which saves space. However, it can cause "flash rusting" on certain ferrous surfaces and is slower than blasting only with air. It's very useful for improving the surface finish due to the smooth and consistent result gained from adding water to the process.
The absence of dust is also a plus point, especially for electrical components as it prevents them from getting re-contaminated and also lowers the chance of a dust explosion.
Wheel Blasting
Wheel blasting utilises centrifugal force to propel abrasive materials against surfaces. It involves a spinning wheel that throws the abrasive into a confined cage at remarkable speeds. Without using any compressing propellants, this process is commonly referred to as airless blasting. Wheel blasting is a very efficient method which utilises recyclable media for prolonged periods.
However, unlike a conventional blast chamber, wheel blasting is more appropriate for repetitious items or forms. Many aspects of wheel blasting are the same as other abrasive blasting techniques, but it also varies considerably in several significant areas.
Instead of using highly pressurised air, the abrasive is applied to the steel item through a spinning wheel, making wheel blasting highly effective for preparing or cleaning steel with various abrasives.
Across many, blasting grit, corundum, glass and plastic are frequently used. Wheel blasting also offers adjustability in the force and speed at which the abrasive is applied to the surface. Throughout the preparation process, the abrasive applied via the revolving wheel is rapidly removed and reused. Consequently, this process leaves less residue after cleaning and reduces the quantity of abrasive used.
Bead Blasting or Shot Peening
Bead blasting, often referred to as "shot peening", is a unique method used to create surface dimples in divers objects. This process involves the application of circular media and is similar to grit blasting, but is primarily focused on plasticity rather than abrasion for material removal, thus producing less contamination in the form of dust.
A major advantage of shot peening is its ability to enhance the compressive strength of both metal and composite materials by reducing their tensile stress.
This technique is particularly beneficial for delicate machine components such as turbine blades, suspension springs and gears, preserving their structural integrity and extending their lifespan.
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