How Particle Analysis Affects the Shot Peening Process
Manufacturers that produce products that incorporate metallic elements have one thing in common: the concern of creating a product that will stand the test of time. This encourages them to use high-quality materials and techniques designed to preserve the integrity of the metals that are used.
Shot peening, for example, is a decades-old technique used to strengthen various parts that are used daily, such as car parts, landing gears in airplanes, and springs in various equipment.
But what exactly is shot peening, and how does it fit within the world of particle analysis?
As pioneers of the particle analysis industry with 140 years of experience, W.S. Tyler has the know-how needed to enhance various operations used throughout the world, including your shot peening process.
It's for this reason that this article will cover:
- What shot peening is
- How particle analysis benefits shot peening
- How to apply particle analysis to your shot peening operation
- The common mistakes that are made when using particle analysis to your shot peening operation
What Is Shot Peening?
During the era of horse and buggy transportation, engineers discovered that they could use the ball end of a peen hammer to increase the life of the springs used for the buggies by simply hitting the spring. This eventually evolved into the shot peening techniques used today.
Shot peening itself is the act of relieving stresses found in various metals. The process involves putting several impingement marks on whatever material you're peening to prevent stress cracking from occurring.
How Does Particle Analysis Benefit the Shot Peening Process?
When shot peening material, a particle is taken and is projected at the surface to be peened until the desired coverage is achieved. These particles can be made of various materials; however, a steel shot is the most commonly used material.
As the shot used to peen has to be a specific size and shape, particle analysis must be used to ensure the shot you use complies with industry standards.
If you have shot that is not spherical and has edges, instead of leaving dimples in the surface being peened, the shot will leave tears.
Additionally, if you're shot is not the correct size, the effectiveness of the peening process may be hindered. This can either be in the form of the shot not properly impinging the material or the shot leaving dimples that are too larger, damaging the material.
Test sieve analysis, in particular, plays an integral role in the quality control of the shot itself and can help you to implement a shot peening process that produces reliable results consistently.
To the end, the standards your shot peening process should comply with are reflected in your industry standards. This includes information on the size the shot used has to be as well as the percentage of particles that can be out of spec.
It should be noted that as the shot quality goes down, the failure rate of the parts being peened goes up. In other words, if these parameters are exceeded, you will have to replace all the shot in the peening machine.
What Should My Test Sieve Analysis Operation Look Like?
As stated above, test sieve analysis is used as a quality control measure to check the size and shape of the shot being used in your operation. That said, it is vital that you are use equipment that is clean and calibrated.
Now, the first step to any test sieve analysis is to gather an accurate representative sample. When testing shot for the peening process, this involves gathering 100 grams of the shot that will be used.
You will then want to ensure you select the right set of sieves to test your shot. As there are several different shot designations, sieve stack assembly varies.
To provide insight into what you could expect when assembling a sieve stack, let's say your operation uses 230 shot. Your sieve stack would consist of a #18 sieve at the top, then a #20 sieve, followed by a #25 sieve, followed by a #30 sieve, followed by a #35 sieve, and lastly, a collection pan at the bottom of the stack.
To help ensure you are using sieves that comply with your industry standards, review our article: Understanding the Standard Metric and US Sieve Cloth Conversion Table.
You will then want to run your material through the sieve stack using a sieve shaker to promote particle movement. It's at this time that the sieves will separate the shot by size on each sieve.
To begin gathering your sieve results, you will want to weigh the material retained on each sieve. In terms of material retention, all material should pass through the #18 sieve, no more than 2% of material should be retained on the #20 sieve, no more than 50% of material should be retained on the #25 sieve, a minimum of 90% cumulative material retention on the #30 sieve, a minimum of 98% cumulative material retention on the #35 sieve, and no more than 2% material retention in the collection pan.
NOTE: You will also need a magnifying device strong enough to examine the shape of the shot being used, such as a 20x magnifying glass.
What To Avoid When Testing Your Shot Material
The most extensive mistake lab technicians make when testing shot is not using certified test sieves. Having your test sieve certified helps to identify any sieves in your stack the may be out of spec or otherwise comprised in a way that affects your ability to yield accurate and repeatable test sieve analysis results.
Taking bad samples is another common mistake. This often results in false results, which, in turn, can cause your shot peening operation to deliver undesirable results.
Keep Your Test Sieves Pristine To Yield Reliable Results
Shot peening is the process of projecting particles of metallic shot at various materials to relieve stresses in the material. To ensure your shot peening process works as intended, you must implement test sieve analysis in your process to test the size and shape of the shot you use.
That said, once you tailor a test sieve analysis operation to accommodate your needs, you must be sure to use best practices when maintaining your sieves. Doing so will allow your test sieves to produce accurate and repeatable results for longer.
Having helped customers navigate the world of particle analysis for over 140 years, W.S. Tyler is here to help you make the most out of your particle analysis equipment.
To learn how to best maintain your test sieves, review the article: 5 Tips for Maintaining your Test Sieves (Best Practices and Cleaning + Video).
About Ronnie Brown
Ronnie is the Content Writer for W.S. Tyler and has four years of experience as a professional writer. He strives to expand his knowledge on all things particle analysis and woven wire mesh to leverage his exceptional writing and graphic design skills, creating a one-of-a-kind experience for customers.