hardening and tempering
hardening and tempering
(OP)
Hi sir ,
i want to ask that how to controlled ferrite % in hardening and quench tempered steel.
after hard and tempered structure observed tempered martensite with 25% ferrite plz tell how to control ferrite level
i want to ask that how to controlled ferrite % in hardening and quench tempered steel.
after hard and tempered structure observed tempered martensite with 25% ferrite plz tell how to control ferrite level





RE: hardening and tempering
RE: hardening and tempering
What is the section size?
What time/temperature are you using for hardening?
What time/temperature are you using for tempering?
Without knowing these, all we can do is guess at your problem.
rp
RE: hardening and tempering
RE: hardening and tempering
steel composition is C%-0.43,Mn%-0.82,Si%-0.23,S%-0.014,P%-0.032 EN8D grade,
Socket 831 Pc Wt is 1kg200gm,loading per tray was 60 pc in hardening(continues furnace 7 tray)(4back and 3front in soaking area)
time 2hr 20min (including soaking time 1 hr) temperature-860 degree oil temperature-46 degree hardneing hardness-229-255 BHN
tempering temperature 580 degree/ time soaking 1hr 20 min,hardness achived 207-241 BHN
RE: hardening and tempering
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
rp
RE: hardening and tempering
- decrease quench temperature--> depending on the oil, you may want to go even lower than the 40 C suggested by Arun
- increase quench agitation--> Use the maximum agitation/impeller rpm possible within the quench tank
- increase the time in the quench tank--> it is possible that the parts are not in the quench tank for a sufficient duration
Have you tried a smaller load with the current furnace settings and quench parameters? I would not increase the austenitizing temperature above 860 C. The standard range is 800-860 C for this type of steel (SAE 1045, C45E EN 10083-2, S45C JIS G4051), and since there is likely not a long quench delay with a continuous furnace, this is unlikely to be helpful, and may lead to cracking problems if a more aggressive quench is used.RE: hardening and tempering
How long does it take to move from the furnace to the quench tank?
RE: hardening and tempering
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: hardening and tempering
RE: hardening and tempering
If this is a sealed quench furnace, then there is a quench delay when the parts are moved from the heating chamber into the vestibule prior to quenching. However, I doubt that the delay is so significant that the temperature is dropping below 800 C if the full load has been properly soaked to achieve 860 C. If there is a significant delay, say more than 20 seconds, then this should be investigated together with the quench details.
RE: hardening and tempering
RE: hardening and tempering
http://www.pearson-studium.de/books/3827370597/cd0...
While the composition for the steel in the diagram is slightly lower in Carbon and Manganese, it is close (0.39C and 0.72Mn vs 0.43C and 0.82Mn, which would shift the curves to the right). If you are seeing an as-quenched hardness of 229-255 HBW, this diagram would suggest the microstructure is ferrite and pearlite. No martensite would be expected. The pearlite would be very fine and difficult to resolve with an optical microscope. Are you sure you are looking at 25% ferrite 75% tempered martensite?
rp
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
I met the problem like this in the past (steel C35).
Metallography should be very helpful. I suppose that there is a mixture of pearlite and ferrite, no martensite.
RE: hardening and tempering
Finally, have you confirmed the chemistry? It is not inconceivable that you could have a mixed steel.
RE: hardening and tempering
and furnace is not sealed quench its continuous furnace.7 tray area in furnace and each tray come out after 20 min
RE: hardening and tempering
required hardness is 201-255 BHN after tempering
and after tempering hardness come is 207-241 BHN
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
how much quench hardness should be.it should be higher side for less ferrite
how much quench oil temperature and how much quench delay should be
RE: hardening and tempering
oil acidity is 0.40
RE: hardening and tempering
RE: hardening and tempering
It baffles me, that for a thin sectioned medium carbon steel material, low hardness is a issue.i would have expected discussions, regarding cracking or methods to lower hardness.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: hardening and tempering
how much quench hardness should be.it should be higher side for less ferrite
how much quench oil temperature and how much quench delay should be
RE: hardening and tempering
The other questions can be determined by looking at a CCT diagram. Referring to the CCT diagram referenced to from my post on 7 Jan:
A cooling rate that would produce 50% ferrite, 50% pearlite with an as-quenched hardness of 95 HRB (215 DPH) will get your from 845C to 100C in two minutes. Since this is unacceptable, two minutes in the quench should be sufficient. I like overkill on quenching, so you could consider 10 minutes in the oil. It wouldn't hurt and would make sure the quench time is not your problem. If you need to shorten it to maintain the cycle time for furnace, that should be OK, but I wouldn't want to go less than 5 minutes.
From the diagram, a mixture of 10% ferrite 90% pearlite would give you an an-quenched hardness of 21 HRC (242 DPH). 10% ferrite and the other 90% a mixture of bainite and pearlite would be 28 HRC (284 DPH). I'd assume DPH is 10KG Vickers. This tells me that you should be aiming for around 28 HRC as-quenched.
Now, understand that the diagram is not for your exact chemistry. You have a bit more C and a bit more Mn. Both of these will affect the results toward higher hardensses and longer transformation times. This is why I;d use 10 minutes in the quench. The higher carbon and manganese will increase your hardness targets, too, so you could consider an as-quenched hardness range of 28-32 HRC; that is if you are below 28 HRC, you probably will have too much ferrite and you should be closer to the 32 to make sure your process stays in control.
rp
RE: hardening and tempering
RE: hardening and tempering
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: hardening and tempering
RE: hardening and tempering
As for being a contrarian, I was taught long ago that generally held opinions are great for understanding things, generally. But, when you start dealing with specific problems, general opinions often can be misleading.
rp
RE: hardening and tempering
RE: hardening and tempering
As quench 863degree,as quench hardness 255-302BHN ,oil temperature 39-52 degree.
Tempering Temperature 620 degree hardness achived 207-241 BHN specified hardness 201-255 BHN
customer told that 730 N/mm2 UTS Pc break and 830 N/mm2 pc not break.
plz tell me how can be analysed.
when hardness increase UTS all most will increase than should change material S45C against EN8D or other option.
RE: hardening and tempering
RE: hardening and tempering
What are the requirements you are trying to satisfy?
RE: hardening and tempering
Similar to redpicker comments: The hardness range achieved (207-241) is within the hardness range required (201-255) and thereby meets the specs. What's the problem??
RE: hardening and tempering
actually customer told that part is break our process is ok everything hardness to micro.but he want to asked if part break and heat treatment is ok hardness is ok micro is ok than should increase hardness specification and or change grade for increase UTS becoz 800N/mm2 UTS part is not break and 730N/mm2 part was break.
so i want to suggestion from ur side what can i do.
RE: hardening and tempering
he told that 730 N/mm2 pc break and 830 N/mm2 pc was not break means he asked to her what can change process or material or other that improved UTS or part are not break
RE: hardening and tempering
RE: hardening and tempering
So, you want to change the material so that minimum hardness is 235 (UTS 800N/mm2), correct?
You will need a range of hardness. If you were 201-255 BHN, let's say now 235-285 BHN.
With your process, you will drop about 50 BHN during tempering. So, you will want your as-quenched hardness to be around 285-341 (or higher).
You can probably get there with just increasing C and Mn. If you try to raise the C very much, however, you can risk cracking. I don't know what steels are available to you. You will probably want to limit the carbon to around 0.47 max. I'd try to find something around 0.45 C and 1.00-1.25 Mn.
Good Luck
rp
RE: hardening and tempering
rp ji
RE: hardening and tempering
part name Socket 304 wt per pc 0.520kg,material used EN8D C%-0.42, Mn%-0.85 and Raw material hardness is 179-187 BHN
loading per tray is 180 pcs
normalising temperature is set 860 degree and time 1hr 20min soaking ,7 tray furnace
part hardness required 162-210 BHN and hardness observed 156-170 BHN only proper fan cooling
than increase temperature 10 degree than little bit hardness achived 163 BHN
so plz suggest to me what can i do to improved hardness.
RE: hardening and tempering
and pc wt is 0.320kg loading 300 pc per tray.becoz specification is 175-220 BHN .material used EN8D C% 0.42,Mn%-0.86,Si%-0.25
RE: hardening and tempering
For socket 220, what do you mean by burn?
RE: hardening and tempering
so plz tell me its ok or not .
and how much degree temperature can varies.and how much permisible deviation should be
RE: hardening and tempering
RE: hardening and tempering
example:-SKT 609 Specified hardness 241-295 BHN
1-hardening temperature -862°C (Spec.860±10°C) & socking time 1 Hr.
2-Micro structure –Tempered Martensite with % of Ferrite 10
3-As Quench hardness – 514-601 BHN
4-TemperingTime(Socking) – 1 Hr. 20 Mints. & Temperature-680°C (Spec. 450-680°C)
5-As Tempered hardness-269-285 BHN
structure will affected or not in tempering in 680 degree
RE: hardening and tempering
As your hardness is within range, I am not sure why you want to increase tempering temperature.
rp
RE: hardening and tempering
and i want to just ask to u plz tell me can i do tempering at higher temperature and what effect in structure
RE: hardening and tempering
How much do you have to lower the hardness? Have you tried to increase the tempering time at 680C? You might find that doubling the tempering time at 680C will solve your problems and you will not have to worry about harm to the microstructure.
rp
RE: hardening and tempering
As Quench hardness – 514-601 BHN than lower hardness have range with in spec 241-295 BHN in temered.
yes i hv done at 680 degree temperature to lower the hardness
after tempering hardness come 255-269-285 BHN
means there is no bad effect in micro structure and no ferrite increase if we will go upto 690 degree in tempering
thanks rp ji
RE: hardening and tempering
plz tell me how to fix tempering temperature for diff part and different grade becoz tempering temperature depend on as quench hardness and as quench hardness depend upon carbon percent and other alloying element.
so plz tell me how to fixed temperature of tempering.
RE: hardening and tempering
sorry to come very late..
how r all of u..
anyway sir i want one simple question if i will tempered part in temperature 450°C and 400°C than what effect on structure and other properties.
and can i tempered my part at this temperature
what should be range of tempering temperature.
thanks,
atibha
RE: hardening and tempering
can i increase soaking time than effect in ferrite %
and oil temp. we can same kept 50°C .
RE: hardening and tempering
To decrease ferrite, you need to have high quench severity (high austenitizing temperature, low quenchant temperature, high quenchant agitation). Increasing the soak time will not affect ferrite in the final structure.
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
RE: hardening and tempering
please suggest to me for reduce decarburization.
actually new development item i have hard n tempered.
but in final micro observed fully decarb.
its socket Wt. 800gm Spec hardness 201-255 BHN