4 ms·

Now that nature lets you read articles for free you can actually go and read the original paper. In the paper the authors had to heat treat the steel at 900 °C

by wycx 12y ago

Now that nature lets you read articles for free you can actually go and read the original paper. In the paper the authors had to heat treat the steel at 900 °C for 15 mins to generate the microstructure that gave the properties they wanted. So, what does welding do to the microstructure? Does this material need to be heat treated again at 900 °C after welding? Does the the hard-but-brittle B2 intermetallic reform in the HAZ?

TheCraiggers 12y ago
Interesting question, although I'm not sure it applies much in the real world. Aren't the welds themselves typically the weakest link in a build? Seems like the engineering tricks used to keep welds under stress from ripping apart would also benefit the affected metal in the HAZ.
- chromaton 12y ago
  Welds can be stronger than the HAZ. See this video from Lincoln Electric on welding chrome-moly: http://youtu.be/W5dVAT9PTmw?t=7m53s http://youtu.be/W5dVAT9PTmw?t=7m53s
  - djcapelis 12y ago
    Yep! Generally if your weld breaks before the material in the HAZ it is considered a bad weld and certified welders working under structural standards are generally required to produce welds that are stronger than this. (Not actually a certified welder right now, but I have a brief familiarity with the D1 structural standards as getting a cert is something I've looked into.)
rsfern 12y ago
That's a really interesting question, and I'm not sure what the answer should be. According to the authors, the B2 intermetallic forms in small particles during recrystallization at 900 C because of the influence of the nickel, so you might expect a similar high rate of particle nucleation in the wake of the melt pool, resulting in small, dispersed particles. Then again, you might get coarse intermetallic phases instead, resulting in a brittle weld. In either case, the advantage of the B2 particles is that they allow a high degree of strengthening during work hardening, which would be done before welding. Any subsequent heat treatment would tend to undo that work hardening.

by wycx 12y ago

TheCraiggers 12y ago

Interesting question, although I'm not sure it applies much in the real world. Aren't the welds themselves typically the weakest link in a build? Seems like the engineering tricks used to keep welds under stress from ripping apart would also benefit the affected metal in the HAZ.

chromaton 12y ago
Welds can be stronger than the HAZ. See this video from Lincoln Electric on welding chrome-moly: http://youtu.be/W5dVAT9PTmw?t=7m53s http://youtu.be/W5dVAT9PTmw?t=7m53s
- djcapelis 12y ago
  Yep! Generally if your weld breaks before the material in the HAZ it is considered a bad weld and certified welders working under structural standards are generally required to produce welds that are stronger than this. (Not actually a certified welder right now, but I have a brief familiarity with the D1 structural standards as getting a cert is something I've looked into.)

rsfern 12y ago

That's a really interesting question, and I'm not sure what the answer should be. According to the authors, the B2 intermetallic forms in small particles during recrystallization at 900 C because of the influence of the nickel, so you might expect a similar high rate of particle nucleation in the wake of the melt pool, resulting in small, dispersed particles. Then again, you might get coarse intermetallic phases instead, resulting in a brittle weld. In either case, the advantage of the B2 particles is that they allow a high degree of strengthening during work hardening, which would be done before welding. Any subsequent heat treatment would tend to undo that work hardening.