Thought it might be interesting to share a little experiment. I bought a 32cm and 28cm Mineral B Carbon Steel pans and was interested in the temperature distribution over time. I used an infrared thermometer.
Below is a graph of temperature vs time. I measured at the center, "inner ring", and outer edge.
I used setting "8". The highest setting is 9.
I used the same heat hob on my ceramic flat-top. Wish I had a gas cook-top....
One questions is that am I heating the pans too high? I'm guessing not? For both pans the I turned off the heat when the temperature was approaching 350C at the center, which is also when the oil started visibly smoking.
Overall I'm reasonably happy. The center was clearly the hottest but the overall distribution and trend with time seems to be quite steady and even.
No surprise that the center of both pans are showing browning but the outer parts are still mostly silver.
Next time I want to do the experiment on a gas cooktop at a friend's place. I do expect that the heat distribution to be much more even.
Hope you find this information and the graph below useful!