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Tempering of low carbon steel

Tempering of low carbon steel

Tempering of low carbon steel

(OP)
I have got a quench and tempered low carbon steel. The microstructure like pearlite + ferrite. Shouldn't it be tempered martensite?

Can someone provide me some useful information about quench and tempering microstructure?

thx

RE: Tempering of low carbon steel

What is the carbon content of the steel and what was the quenchant?

RE: Tempering of low carbon steel

How low is the carbon and what other alloying elements are there in the steel? In what medium was the steel quenched and finally the section thickness?

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

RE: Tempering of low carbon steel

(OP)
The material is 0.13% carbon, quench in water, tempered at 650C

RE: Tempering of low carbon steel

(OP)
The section is 1 inch cube, tempering for 1hour,
Mn1.3, Si0.25,Cr/Ni0.14,Mo0.2

RE: Tempering of low carbon steel

You do not have sufficient carbon content to form any appreciable martensite.

RE: Tempering of low carbon steel

Fine grained ferrite with isolated grains of pearlite.  I don't believe that a steel of that lean an alloy composition and low carbon content can achieve any martensite.  The nose of the CCT curve that you must pass during quenching to get martensite is probably off the graph.  

RE: Tempering of low carbon steel

SAE 1513 is a carburizing grade of steel. Forged camshafts is one application I remember. The microstructure you report is typical for this material.

RE: Tempering of low carbon steel

(OP)
Thanks for everyone!

In fact, I had 3 samples, which are same materials.

I had them for different heat treatment. Quenching, quenching_tempering at 580, and Q+T at 650.

The  just quenched one shows there are some martensite formed.

For 580C I think it is the tempered martensite structure.

But for 650C, the pearlite come, and I do not understood.

Thanks again  

RE: Tempering of low carbon steel

(OP)
The material is a ASTM 694, F65. used in flange and pipe.

RE: Tempering of low carbon steel

Can you post some microstructure photos? At 650C you are approaching a spheroidizing treatment, which might explain what you are seeing.

RE: Tempering of low carbon steel

I agree with dbooker630-- 650 C for such a low carbon steel will likely result in spheroidizing of any carbides that may be present.

RE: Tempering of low carbon steel

(OP)
I hav attached some micrograph of 650.

If you can not access to it, please let me know your emails please.

Thanks

Also, as I am a graduate working in the metalurgy area. Is there any good way to ahieve knowlage and experience like you guys as fast as possible?

RE: Tempering of low carbon steel

Can you save the file in an earlier version of PowerPoint? I don't have Office 2007.

As far as your second question, there is no shortcut. Thirty years ago I was in your shoes, the best thing I can say is to work with metallurgists that do have the experience. Not everything is in the textbooks.

RE: Tempering of low carbon steel

leizhou,

Can you confirm the etchant and the magnification of the image?  I believe this is spheroidized carbides in a ferritic matrix, but the magnification appears to be quite low.  Can you obtain higher magnification?

RE: Tempering of low carbon steel

(OP)
Thanks again.

I use to think this is a spheroidized phase, but I do not think the time 1 hour is enough for it. Also, a testhouse call bodycote say that is pearlite.

I really wish to learn from other metallurgists but I am the only "metallurgist" as my company is a design based.

I have attached the file in 2003 version.

Thanks

RE: Tempering of low carbon steel

leizhou,

I just downloaded a PPTX viewer and I agree with TVP. If you can get a 500X shot we can confirm the structure for you.

RE: Tempering of low carbon steel

(OP)
this image is under x400, I will try further. that takes me time.

Thanks

RE: Tempering of low carbon steel

If you were able to get any martensite after quench it would become tempered martensite at the 650 C temper. Yes it would take more than 1 hour to spheroidize it. Hypoeutectoid steels have a mixed ferrite/pearlite structure .After HT , depending on the conditions you can get interesting structures .The structure below is a hypoeutectiod steel [ Japanese sword] with ferrite grains surrounding a grain [originally pearlite] of pearlite at the edges and martensite in the center.

RE: Tempering of low carbon steel

leizhou,

It is difficult to tell from the photomicrograph. It could be highly tempered martensite but more resolution is needed.

RE: Tempering of low carbon steel

Based on CCT curves I looked at, you can't cool a plain carbon steel with 0.13% C fast enough to get martensite.  The first micro is over etched, the second micro is under etched.  Higher mag won't help, but could confuse.  You should be able to discern microstructure at 100x.  You must be working with BodyCote out of Chicago area.  

RE: Tempering of low carbon steel

I disagree with Metalmeister that higher magnification won't help, but it is dependent upon having a properly prepared sample, meaning well polished, uniformly etched, appropriate lighting, correct focus on microscope/camera, etc.  None of these items appears to be correct for the second image.  

RE: Tempering of low carbon steel

leizhou,

Hello. What is the etchant you are using? Also, are you aware that Mn is austenite stabilizer? Perhaps with this carburdizing alloy you cannot form martensite using water as a quenching agent. What is the Ms Temperature for this alloy? Maybe it's below room temperature.

About the microstructure you presented. You have to be careful with ductile materials when polishing. It's very easy to generate polishing artifacts. Also, please when you present a micrograph put in a marker for scale.

Best Regards

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