Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Musings on barrel life...
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Dzaw" data-source="post: 144361" data-attributes="member: 7794"><p><strong>Re: Thanks!</strong></p><p></p><p>"as a side note CM barrels don't have any carbide in them but carbon thats what makes them harder"</p><p></p><p>I hate to slit hairs, but I feel I must for the sake of accuracy...</p><p></p><p>CM stands for Chromium and Molybdenum. The chromium content is not nearly as great as in stainless, but it's there. Among other things, it helps push the pearlite nose on the isothermal transformation curve farther off in time, making it more thoroughly hardening, so a uniform hardness can be had throughout the workpeice.</p><p></p><p>The carbon content IS much greater in CM than in the stainlesses we are used to seeing, but ALL steels have carbon. Steel, by its very definition is the alloy of carbon and iron.</p><p></p><p>Chromium LOVES carbon, and chromium carbide is the result. Yes stainless barrels have carbides in them. Yes CM barrels have carbides in them. What makes CM barrels harder is nit the carbon content. That makes it ABlE to be harder. What makes it harder is the heat treat.</p><p></p><p>Bear in mind that different steel alloys display different levels of tougness (which is the opposite of brittleness, and has nothing to do with strength or hardness) at given hardness levels. A CM barrel wears more quickly not because it is harder, but because it lacks chromium in sufficient quantities to resist the chemical action in the erosion process, which happens at a much accellerated rate under heat and pressure.</p><p></p><p>With equal toughness and equal corrosioin resistance, a harder steel will wear out slower. Or, alternatively, with equal hardness and equal corrosion resistance, a tougher steel will wear more slowly. Finally, (yep, you guessed it) with equal hardness and equal toughness, a more corrosion resistant steel will wear more slowly.</p><p></p><p>This is why I like the idea of crucible's high purity modified 17-4. With appropriate heat treat It can be tougher, harder, AND more corrosion resistant than 416R</p><p></p><p>Remember that fully annealed, all of these steels are way too soft to use. Hardness is your friend, so long as it does not compromise other mechanical properties that are critical. Toughness is also your friend, in the same way, as is corrosion resistance.</p></blockquote><p></p>
[QUOTE="Dzaw, post: 144361, member: 7794"] [b]Re: Thanks![/b] "as a side note CM barrels don't have any carbide in them but carbon thats what makes them harder" I hate to slit hairs, but I feel I must for the sake of accuracy... CM stands for Chromium and Molybdenum. The chromium content is not nearly as great as in stainless, but it's there. Among other things, it helps push the pearlite nose on the isothermal transformation curve farther off in time, making it more thoroughly hardening, so a uniform hardness can be had throughout the workpeice. The carbon content IS much greater in CM than in the stainlesses we are used to seeing, but ALL steels have carbon. Steel, by its very definition is the alloy of carbon and iron. Chromium LOVES carbon, and chromium carbide is the result. Yes stainless barrels have carbides in them. Yes CM barrels have carbides in them. What makes CM barrels harder is nit the carbon content. That makes it ABlE to be harder. What makes it harder is the heat treat. Bear in mind that different steel alloys display different levels of tougness (which is the opposite of brittleness, and has nothing to do with strength or hardness) at given hardness levels. A CM barrel wears more quickly not because it is harder, but because it lacks chromium in sufficient quantities to resist the chemical action in the erosion process, which happens at a much accellerated rate under heat and pressure. With equal toughness and equal corrosioin resistance, a harder steel will wear out slower. Or, alternatively, with equal hardness and equal corrosion resistance, a tougher steel will wear more slowly. Finally, (yep, you guessed it) with equal hardness and equal toughness, a more corrosion resistant steel will wear more slowly. This is why I like the idea of crucible's high purity modified 17-4. With appropriate heat treat It can be tougher, harder, AND more corrosion resistant than 416R Remember that fully annealed, all of these steels are way too soft to use. Hardness is your friend, so long as it does not compromise other mechanical properties that are critical. Toughness is also your friend, in the same way, as is corrosion resistance. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Musings on barrel life...
Top