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  • 1.  Q/A from recent Struers webinar

    Posted 09-19-2022 16:24
    Thank you those who attended my last webinar entitled: Weld Bead Inspection for the Production Environment. Here is a link in case you missed it.

    Below is the Q&A from the webinar. Please reach out if you would like additional information. @Kelsey Torboli 

    1. My lab has a Labotom-15 and you mentioned a Labotom-20. This machine looks much bigger and has different extension boxes. What are the differences?
      1. Yes, the Labotom-15 was retired and the new generation Labotom-20 was released. Both machines take a 14" diameter cutoff wheel and are used for manual sectioning. The Labotom-20 has some big improvements, like the addition of a line laser for placement of the samples. The Labotom-20 also has a redesigned hood that allows for left and right-side extension boxes, while the Labotom-15 only accepted a left-side safety extension box. In terms of user experience, the Labotom-20 has a similarly simple user interface of three buttons and a flushing gun for easy cleaning at the end of a shift.
    2. When using the MD-Pianos, can you explain how often to dress?
      1. Yes, the MD-Pianos ship with an aluminum oxide dressing stick that is used to restore the MD-Piano's aggressiveness. Overtime, the embedded diamonds may get covered with metal debris or mounting resin, so the dressing stick helps to clear the debris, so the abrasives are fresh and ready for grinding. The frequency of dressing will depend on your material hardness and if the samples are mounted or unmounted. For example, 6 solid 30mm diameter specimens that are softer than 450 Vickers should be dressed every 10 minutes, while the same size solid samples with hardness greater than 450 Vickers should be dressed every 5 minutes. The MD-Piano's box includes a helpful info booklet with a handy table for dressing frequency.
    3. My lab has an AbraPlan for grinding of samples, then polishing on Tegramin. Will the heat from the grinding process affect my weld's heat affected zone?
      1. No, if everything is working properly, then the grinding process should not affect your sample's microstructure or properties. There are a few things you can verify to make sure. Firstly, check to make sure that water is flowing during the entire stone grinding process. AbraPlans are usually paired with a recirculation tank, so make sure this is filled up with water. Also, check which stone you're using for the grinding process and verify that it matches your sample material. Struers offers different stones for nonferrous, ferrous, and other materials. When using a grinding stone, be sure that the AbraPlan's diamond dresser tip is dressing the grinding stone regularly. Depending on your machine generation, you may set it up so the dressing arm travels back and forth across the stone every 15 seconds or after every 100um of material removal.
    4. My company mounts our weld samples because we need to do measurements and also hardness testing. What level of polish would you recommend for this?
      1. For dimensional checks and if your weld is larger, you may be able to see everything with preparation through #1200 grit. For the hardness testing, this is a little more complicated. If your hardness load is quite heavy, like 10 kilogram Vickers, then a coarser finish is usually OK. For lighter loads, like 500 gram Vickers and below, you'll need a finer finish to resolve the corners of the Vickers indent.
    5. My lab has an AbraPol-20 with a large 200mm diameter sample holder for my large welds. In your slides for the steel welds, you showed a holder with three large rectangle cutouts. Is this holder still available?
      1. Yes, this is a 200mm diameter holder called the MAXOT. It's made of stainless steel, so it's recommended for heavy use in rugged environments. Here at Struers LLC., we are also able to make customized holders for complex sample geometries. Definitely get in touch with your local sales rep for more info on the MAXOT pricing or the custom made holders.
    6. Can you explain how the action limits work in the StructureExpert Weld software? This might be a useful addition to my system.
      1. Sure, so the action limits give us the additional yellow color classification. The yellow can be setup to warn me when my results, like leg length, are no longer in the green ideal zone and are drifting towards failure. As the values drop away from the green ideal zone, the yellow zone can alert me so I can make changes in the weld cell. In another case, let's pretend I'm a sub-supplier to a big three automotive manufacturer. I want to be doubly sure that all of my parts are accepted by my customer, so I hold myself to higher standards than the automotive company. Values that pass the automotive company's requirements would show up as yellow, while parts that meet my more strict specifications show up as green and ideal. If you'd like more clarification, feel free to reach out to your local sales representative and we can setup a webex to review your specific weld standards and show you how this module might meet your needs.
    7. Is it necessary to etch the weld to expose the penetration depth?
      1. Yes, it's normally required to etch the welds. The ASM handbook and can make great recommendations, including the etchant recipe and application method. Some etchants require a controlled swab etch while others are fine with a "dunking" method. As a general rule, 5% nital is great for most carbon steels. But when in doubt, I recommend the ASM handbook or other literature resource.
    8. When I prepare my welds, do I always need to dose lubricant with my diamond suspension?
      1. For this, it'll depend on what type of diamond product you have. In my methods for the aluminum welds, I've used DiaPro. Our DiaPro product contains diamond and lubricant in one bottle, so setting the dosing rate is much easier! The only downside of DiaPro is that is does contain water, and should not be used by customers with water-sensitive samples. Alternatively, you may dose from diamond and lubricant in separate bottles. These products may be alcohol-based and help me avoid any dissolution of water-sensitive inclusions in my material. The downside to separate diamond and lubricant is that the user must get the ratio of diamond and lubricant just right. When it comes to dosing, I always recommend the finger swipe test. Take a clean and dry finger and swipe it across your 9um or 3um surface. If your finger comes away bone dry, you must increase the dosing. If your finger is dripping with diamond suspension, you must reduce the dosing rate as you are wasting suspension!
    9. For etching, I've read that you have a system that can etch stainless steel welds using acid and voltage together. Can you describe this process?
      1. Yes, this process is called electropolishing and combines an electrolyte with an applied voltage for a specific amount of time. Stainless steel is notoriously resistant to chemical attack, which is why it's often chosen for tanks and pipes that carry corrosive chemicals. However, this resistance to chemical attack also makes it difficult to etch! For an in-lab machine, we'd recommend the LectroPol with the external etching device. For stainless steels, we usually recommend filling the external etching dish with 10% oxalic acid and using special tongs to hold the SS sample in the oxalic acid while voltage is applied for the preset time. I presented a webinar on stainless steel preparation recently, so I can send you the link.
    10. You mentioned the StructureExpert Weld can be used for a Gage R&R study. Can you elaborate a bit more on how that works?
      1. Let's start with bit of background for those who are not familiar. A Gage R & R stands for gage repeatability and reproducibility. It's a statistical tool that can measure the amount of variation in a measurement system, both from the measurement device and technicians taking the measurement. In the case of the StructureExpert Weld, a group of technicians are presented with the same 10 images, usually presented in a random order. Each technician measures all 10 welds in turn and ideally they are given the exact same directions and measure the weld without any outside influences that could affect results. After the data is collected, it's analyzed to determine how repeatable and reproducible the system is. Many companies perform a Gage R&R anytime a new operator or technician begins working. It's also a useful tool to repeat annually for all weld technicians to ensure the system continues to be repeatable and reproducible.

    Kelsey Torboli
    Struers Inc.
    Avon Lake OH
    (440) 241-2658
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  • 2.  RE: Q/A from recent Struers webinar

    Posted 09-20-2022 00:31
    Thanks for sharing your knowledge. Thanks again

    Jaspal Singh Gill

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