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Toughness of CPM-154

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Larrin

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RDalman

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Since I'm making cutters for my lathe this thought rose; It would be interesting to see how a high tempered hard sample compares. I mean one ~540c tempered at ~63 hrc.
I know some corrosion resistance is sacrificed, but are there measurable perks beside the heat resistance I wonder.
 

Larrin

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Since I'm making cutters for my lathe this thought rose; It would be interesting to see how a high tempered hard sample compares. I mean one ~540c tempered at ~63 hrc.
I know some corrosion resistance is sacrificed, but are there measurable perks beside the heat resistance I wonder.
In our testing of Z-Wear a 400F temper had better toughness than a 1000F temper when at equivalent hardness. I don't know if that is universal, but at the very least I know that a 1000F temper does not necessarily lead to improved toughness. That knowledge combined with the reduction in corrosion resistance means that I don't recommend the high temperature tempering range, especially for stainless steels.
 

RDalman

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In our testing of Z-Wear a 400F temper had better toughness than a 1000F temper when at equivalent hardness. I don't know if that is universal, but at the very least I know that a 1000F temper does not necessarily lead to improved toughness. That knowledge combined with the reduction in corrosion resistance means that I don't recommend the high temperature tempering range, especially for stainless steels.
Well for my lathe cutters today anyway I thought to myself that they where seemingly damned nice.. Fairly easy to grind at a 65 hrc, if retention is high and toughness seems acceptable, the ease of sharpening might be something to consider.
 

Larrin

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Well for my lathe cutters today anyway I thought to myself that they where seemingly damned nice.. Fairly easy to grind at a 65 hrc, if retention is high and toughness seems acceptable, the ease of sharpening might be something to consider.
You did a side-by-side comparison of sharpenability of low and high temper of similar hardness?
 

Larrin

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No I just thought to myself it felt like it might be the case.
They should be roughly equal in terms of “grindability” and “polishability.” Higher hardness can make the edges more crisp in sharpening so that could be the difference you are seeing. Another possibility is if you are successfully reducing retained austenite with the upper temper which makes deburring easier. Cryo is very important of course with low tempers to minimize RA.
 
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RDalman

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They should be roughly equal in terms of “grindability” and “polishability.” Higher hardness can make the edges more crisp in sharpening so that could be the difference you are seeing. Another possibility is if you are successfully reducing retained austenite with the upper temper which makes debuting easier. Cryo is very important of course with low tempers to minimize RA.
I know... guess I will have to make identical samples through different HT and compare simply, sometime.
 

inferno

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will there be some high temp tempering tests? i mean one could simply do the existing coupons at higher temp and be done. imo i feel its warranted. 154cm is probably designed as a high temp hss steel. a SS HSS more or less.
so it was probably designed with 550C temper in mind from the very start. otherwise i'm willing to buý some rwl for dalman to test. in his area there are a lot of really high end steel makers such as uddeholm tool and such, and they probably dont work their asses off as it is now. i'm betting 550c will be good for all hss. SS or not.

it not like all other humans before us were idiots.
 

inferno

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also i'd like to add that i dont find a 100% difference in measured results anything special. it happens all the time. its just one data point.

i daily encounter and service machines that has gone like 4-500 or 40-80h before breakdown. in the exact same environment, doing the exact same thing. this is not anything extraordinary at all. for you it might be but in reality its when a pattern starts showing up it get interesting. and even then you cant really tell some of your customers they are idiots now can you.

its only 100% imo. it happens. could be 100 different reasons.
 

inferno

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maybe the preferred testing procedure directs **** in a certain direction?? i dont know.
 

ma_sha1

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Wow, looks like I should be able to cut chicken bone with my ABE-L Gyuto ;)
 

Larrin

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will there be some high temp tempering tests? i mean one could simply do the existing coupons at higher temp and be done. imo i feel its warranted. 154cm is probably designed as a high temp hss steel. a SS HSS more or less.
so it was probably designed with 550C temper in mind from the very start. otherwise i'm willing to buý some rwl for dalman to test. in his area there are a lot of really high end steel makers such as uddeholm tool and such, and they probably dont work their asses off as it is now. i'm betting 550c will be good for all hss. SS or not.

it not like all other humans before us were idiots.
It’s not possible to temper the existing broken specimens and re-break them.
 

Larrin

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also i'd like to add that i dont find a 100% difference in measured results anything special. it happens all the time. its just one data point.

i daily encounter and service machines that has gone like 4-500 or 40-80h before breakdown. in the exact same environment, doing the exact same thing. this is not anything extraordinary at all. for you it might be but in reality its when a pattern starts showing up it get interesting. and even then you cant really tell some of your customers they are idiots now can you.

its only 100% imo. it happens. could be 100 different reasons.
That is a greater deviation than we have seen otherwise, especially after averaging 3 specimens.
 
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