If this is homework then you'll need to show your work. First task: calculate the energy to be removed from the steel. For this you're going to have to look up its specific heat capacity (SHC). Edit it into your question.

OK, so you've got to extract 5.5 MJ. How many kg of air will that take? (Same procedure.) Actually, where did you get your SHC value from? It doesn't look right.

I found this online calculator and just tried to put values: link .. What did I forget to take into account?

Look up the SHC of steel. It's not 1012 J/(kg-K). You've chosen air.

And what do u mean (same procedure.)? It's still unclear to me :( .. How do I incorporate the time (9 mins) it should take to cool down?

I'm stepping you through the procedure. I was bringing you onto calculating the mass of air required when I noticed that your first calculation is not correct. You have to calculate the energy to be removed from the steel first. You've used the SCH for air instead. Start again.

oh I overlooked that.. I changed to steel.. there is new result.

I'm a bit confused.. if I set SHC to AIR.. then the energy is 5.5 MJ ... or should I used something else to calculate this?

ok I think I got your point.. so in the result I will get the mass of AIR , right? but how to take into account that time (9 mins?)

It will be the same mass no matter how long it takes.

OK, so if my calculation is correct then 41 Kg of air is needed.. and now it's just about what type of cooling machine can deliver such an amount of air in that time, right?

Not quite. Your question asks for the volume of air. Look up the density of air ...

Also, be careful with units. Kg is kelvin-grams. Capitals matter.

aha okay so air density = 1.225 kg/m3 .. so V = 41/1.225 .. is that correct?

Correct and that answers the question in the title of your post but your post has the 9 minute requirement so I suspect that you were asked for the required airflow. Calculate m^3/minute.

I'm trying to find some air flow formula but no luck yet..

Um, you've got the volume, you've got the number of minutes. How would you calculate the volume per minute?

aha okay :) ... 33,4 / 9 = 3,7m3/min

Correct.

thank you for your help and time I rly appreciate it.

Note that the question implies that you'll get a linear rate of cooling. In the real world you won't because the cooling rate will decrease as the difference between the steel and air temperature decreases.

Just a comment on your approach: you didn't have a systematic approach to the problem and you got fixated on 9 minutes way to early. Break it down into logical steps.

Is past midnight in Ireland. Goodnight.

yes, clear and i think this result is enough for me ... honestly, this kind of task is out of my focus but I wanted to help to my friend. On the other hand, I really appreciate your approach, because even though I have no knowledge about this topic, it was nice to follow your suggestions and determine it... yeah pretty same for me in Slovakia :) goodnight

I've posted an answer. Please accept that to indicate that your question has been answered.

done