Air tempered Vs Water tempered of steel casting 2

[stanislasdz]

Hi guys !

For the same quenching

What is the difference bettwen air tempering and water tempering on the mechanical properties in steel casting ?

Thanks

 

[salmon2]

In principle, I will say no difference as long as it reached the equilibrium stage but the duration to reach equilibrium will be different for air and water, which can be a minor concern.

 

[metengr]

stanislasdz;
I agree with salmon2 there should be no difference in mechanical properties for steel castings cooling in air versus water after tempering. However, you may induce significant distortion from severe thermal gradients cooling in air versus water, after tempering.

 

[metengr]

cooling in air versus water, after tempering.

Oops, that should state cooling in water versus air. Sorry, I must have had too many beers at my hotel in Denmark.

 

[stanislasdz]

Thanks guys !

 

[GRoberts]

The only difference I can think of is that some alloys that have temper embrittlement ranges below the tempering temperature may tend to embrittle less when quenched in water due to a smaller amount of time spent in the embrittlement zone. This is not very common though, and castings have to be fairly thick for this to be a problem.

 

[arunmrao]

metengr,
Without any of thos delightful liquids intake,I read as water quenching vs air quenching. Perhaps our minds are conditioned to read only what we want/know.

Cheers,Enjoy all those hospitalities that Denmark is famous for(grin).

stanislasdz,
Can you please tell what grade of casting and the reason to select water tempering.

All others,
I agree with your opinions stated.

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[stanislasdz]

Arunmarao :

Today, i was reading a metallurgical study about the G24Mn6 Steel Casting.

In this paper the authors found theses mechanicals properties :

Under theses conditions :

In other side the heat treatemnt of the same grade in our plant give a low value of Rm about 690 Mpa

I don't know why we have 690 Mpa ?

Our conditions are :

Quenching temperature : 900 ° C ( water )
Tempering temperature : 570 °C ( water)

The only difference is that the authors of the study use air tempering whereas we use water tempering in our plant !

This motivate me to ask this question is this a diffrence betwen air tempering and wtaer tempering ?

have any one explanation why we have a lower value of Rm ?

Ps: how can delete my previous post ?

 

[salmon2]

The tempering temperature range of the paper is kind of wide: 520C ~ 570C, you do not know really what was the tempering temperature and you were using 570 - the upper limit. +/-10C or +/-5 C are typical for mass production. For lab a better control should be expected.

So very likely your tempered at a higher T than the paper. That is why your strength is essentially lower. You did not mentioned your duration of austenitizing and tempering, but I assume you r the same with paper.

How to delete a post? I just learned this couple days ago:
Red flag your post by "inappropriate post" and comment you wanted to delete it. Then the webmaster will do the job.

 

[stanislasdz]

Salmon2

Here the link to the paper :

http://www.ams.tuke.sk/data/ams_online/2007/number1/mag13/mag13.pdf

I well know that i must reduce the temperature of the tempring to get better value of Rm but i was surprised to see thesse values of Rm in the paper despite they use the same conditions in heat treatment like us !!

Ps: Oupps it's works, thanks for the help !

 

[salmon2]

Were you saying that you think the values of Rm are too high?

I think the numbers are all right.

 

[stanislasdz]

the paper indicated Rm : 700 - 800 MPa

Our values are between 650 en 690 MPa !!!! but we have too high Impact Energy 130 J at - 40 °C !!!

 

[salmon2]

My point is that you do not know what is the tempering temperature in the paper because it gives a heck wide range 520~570.

You said you tempered right at 570C, so let us assume the paper tempered at 570C as well then its Rm should be the lower limit - 700MPa, which is not that different from your range, 650~690 given the material variance.

Your impact energy does seem high, but the paper only gave the min which should correspond to 520C tempering, but didn't give the high number for 570C tempering.

So you may want to temper at 520C in your lab and see if you can match 800MPa and min impact energy.

Also I failed to find the geometry/size info in the paper, do not know if you are the same with the paper. You know the size matters a lot for heat treatment and different spots for tensile and Charpy will promote variance.