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Thread: Testing, testing, 1,2,3

  1. #1

    DevinT's Avatar
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    Testing, testing, 1,2,3

    Started the testing. Forged all of the coupons in CruForge-V. I heated these using an electric furnace to ensure accurate temperature control, I'm glad I did because by eye I would have been a little hotter. Larrin outlined the forging and annealing schedule. Several different temperatures and three different types of anneal cycles were used. Did two samples of each so that we could test both the longitudinal and transverse impact strength.

    Next we will harden and temper using differing austenitizing and tempering temps, then grind all coupons to size and send them to Larrin for the testing.

    Over the years I've done hundreds and hundreds of test coupons in lots of steels. I wanted to do testing that would prove what I've already learned but Larrin has outlined a more accurate set of tests. As we move through the different steels, the testing may change slightly as we learn what is and is not important.

    We will be testing all 12 steels for the search project.

    Including a few shots of forging and starting material.

    Stay tuned,

    Hoss

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  2. #2

    DevinT's Avatar
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    CruForge-V was made by Crucible steel and is one of the newest steels in our testing, only the Vanadis 8 is newer. It was based on O-1 composition with a change from tungsten to vanadium. This steel is quite a bit harder to finish than O-1 and 52100.(more wear resistant) The vanadium and chromium additions are for wear resistance and grain refinement. This steel was developed specifically for knives made by forging.

    This steel has smaller carbides than the blue steels and very fine grain. Our previous testing showed very high toughness similar to 52100. This steel responds well to hardening and sub-zero quenching.

    There are many good carbon steels out there, we felt that this one shows a lot of promise for kitchen cutlery. We bought two tons of this grade because we like it so much. Correct forging temps definitely help this steel reach it's potential.

    Hoss


  3. #3
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    Let the games begin!

    This should be a great thread to watch (and learn from)
    __________
    David (WildBoar's Kitchen)

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    This steel is so much different than the others that we will basically be starting from scratch on the next one, but that's how it goes. A lot of those who forge are interested in maximizing toughness from various forging, annealing, and heat treating practices. The information we are gathering would be very useful to them. We have to decide exactly how the information will be presented, whether all tests will be shown, or if specific heat treatments will be obscured by having "low, medium, high" or similar indicators to show trends without revealing specific temperatures or treatments.

  5. #5
    Senior Member Matus's Avatar
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    2 tonnes of steel ...

  6. #6
    Administrator Angie's Avatar
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    Amazing. That looks like some serious business.

  7. #7

    DevinT's Avatar
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    These are the end of four bars that were forged at different temperatures. They were all normalized the same and then annealed the same. From left to right, the actual hrc of each is 16hrc, 17hrc, 17.5+hrc , and 19.5hrc. Far left coupon had the lowest forging temperature, each one after that had an increase in the forging temperature. Note that there is an increase in hardness correlating with the increase in forging temperature. These are in the normal range of hardness for annealed material. Hardening and tempering from this point may also show different hardnesses for each coupon.

    From here, there are several heat treating schedules for each of the forging temperatures used. Some of these will undergo additional annealing cycles along with pre quenching, differing austenitizing and tempering temps etc. All will have a cryo quench.

    Hoss
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    We have hardness values from the different processing conditions. We are not sharing specific temperatures and times right now. Each graph represents all variables being the same except for whatever is varied on the x-axis. Each was given a cryogenic treatment as well. Decreasing strength with higher tempering temperatures is normal behavior, carbon is allowed to precipitate out of martensite as very small transition carbides which lowers hardness and increases toughness. The peak in hardness with the midpoint austenitizing temperature indicates that at the higher temperature there is excess retained austenite. Which temperature will lead to the highest toughness is somewhat difficult to predict because higher temperatures means less carbide volume which decreases toughness but also higher carbon in solution which decreases toughness. Furthermore, extra retained austenite will improve toughness but is generally thought to be undesireable. What the peak in hardness means for the forging temperature and anneal is difficult to say but may indicate that the carbides are finer for the higher hardness condition, as that can lead to more rapid carbon dissolution during austenitizing. The multiple quench having marginally higher hardness is also expected since we expect both grain refinement and more dissolution of carbides. There are also samples that combine different variables not shown on these graphs. It will be fun to see how the toughness numbers end up!


  9. #9
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    Here are some toughness numbers from different austenitizing and tempering temperatures. The biggest surprise so far is that the material austenitized at 1550°F led to brittle material. This was a surprise because the data sheet recommends 1500-1550°F, which we now believe is too high a range. Alternatively, tempering below the recommended range of 400-500°F did not lead to brittle material but led to a gradual decrease in toughness with increasing hardness. Transverse toughness is about 60% of the longitudinal, which is expected due to the influence of impurities or banding along the rolling direction.



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