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Trouble with Heat Treatment of 1022 steel Fasteners

Trouble with Heat Treatment of 1022 steel Fasteners

Trouble with Heat Treatment of 1022 steel Fasteners

(OP)
I am making special fasteners from 1022 steel.

The screw needs a high surface hardness (58-60 HRc) but should be able to bend also (5-7 degrees).

In my heat treatment process I get the hardness but the screw does not pass the bend test. It is brittle and breaks.

HELP !

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Being able to bend is a very unusual requirement for a screw. Can you give more information about the application? It seems the best approach would be to eliminate the need to bend.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

That's the maximum hardness that you can achieve with this material and of course it is brittle. Have you thought of nitriding or carburizing the surface to meet surface hardness requirements. Then the underlying material's ductility will achieve your ductility requirements. One must question why you need to use 1022 for this purpose.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

I don't believe that as quenched 1022 will make 58HRC.
The answer is surface hardening, either nitride or carburize. The process temp will temper your steel so that it is ductile and the surface will be hard.
1022 does seem an odd choice

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Carburizing or carbonitriding. That is the purpose of this grade.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Maximum possible hardness with 0.22 C is about HRC 45 , depending on thickness , austneitizing temp, quench severity, etc, etc. Gas carburizing is the standard process for ordinary steel screws. It seems like you are carburizing to get above C 45.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

(OP)
The screw I am making is a Self Drilling Screw. 1022 is the standard material.

The screw has to be hard enough to cause the drilling (in 6mm steel plate), then the threads have to tap the steel plate until the flange touches. It should NOT break during the process.

I am doing Carbonitriding, Quenching and Tempering. I am able to achieve a surface hardness of 60 HRc (case is 0.2 mm so the entire thread thickness is kind of through hardened). I then bring the hardness down to about 56 HRc in tempering, but the screw still breaks while tapping. The break is about 3-5mm below the head.

Is the tempering faulty ? What can I do to increase toughness ?

RE: Trouble with Heat Treatment of 1022 steel Fasteners

A case of 0.2 mm is not thick enough to get a HRc test at 60. The surface hardness should be tested with Rockwell Superficial like 15 N or Vickers with a light load. I think the actual surface hardness is higher than HRC 60. I would gas carburize at a carbon potential of about 0.4 % , then the lower carbon in the surface would not be so hard and untough.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

"but the screw still breaks while tapping"

Is this a bending failure, or twisting?

Please show detailed drawings of the screw and some pictures of the failures.
Does the screw cut the threads, or roll-form the threads ?

If the tapping geometry of the screw is incorrect the torque to tap will be excessive.
Ditto if the size of the resulting drilled hole is too small.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

(OP)

RE: Trouble with Heat Treatment of 1022 steel Fasteners

(OP)
This is the screw.
The drill size is pre matched in the front tip.
I think the picture will answer most questions.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

(OP)
To answer “blacksmith”, we are testing on HV1 scale.
The HRc is only conversion.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

HV1 (i.e. 1 kg load) seems pretty high. Using Vickers, it should be more like 100 g (HV0.1) or, as blacksmith suggested, use the superficial tester.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

the size and length of this screw is in adequate to drill and tap .236 thick plate. it's going to break., or fail.
need a bigger fastener. and it may need to use a stiff carbide drill. then tap.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

J-G...

Part of the problem with Your design is that it needs-to-be 'self-drilling-and-thread-tapping'... Yet the screw appears to be ordinary 'self-drilling' for soft-metal/wood installation.

WHAT are You intending to install this fastener into: hard wood??? soft aluminum or low strength carbon steel??? or nickel alloys and titanium??? Etc?? The intended material to be fastened is a very IMPORTANT FACET OF THIS DISCUSSION.

In my humble opinion the drill-tip must be capable of drilling the 'starter/pilot hole' and clearing-away those 'chips'... and then...

The lead-in threads will be required to begin the process of tapping the hole... and then...

The remaining threads MUST be capable of clearing-away new-chips as tapping/insertion progresses.

Sooo…

The lead-in threads should probably 'look like' a hole-thread-tap... and the remaining thread should probably have a way of passing-out [or otherwise absorbing] the chips... possibly with spiral grooves cut thru the thread flanks [lengthwise] or some-other process. Without being abrasively destroyed in the process. My head hurts.

High strength low allow steels [almost tool-steel because of possible friction heating] are probably necessary... with either nitriding or a very hard surface coating such as IVD titanium Nitride to provide high temp friction/wear resistance.

Hmmmmmm… A high strength CRES with nitrogen-surface hardening + wear/abrasion coating... might also be suitable candidate material.

One last possibility is a fastener with fine/hardened threads that is installed in a conventionally drilled-hole that 'cold-works the based-metal hole-wall into a matching female thread-pattern'. This would require a fastener capable of sustained high torque loading during installation. My head still hurts.



Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Did I miss what size the fastener is? Thread size and length?

" the threads have to tap the steel plate until the flange touches... but the screw still breaks while tapping. The break is about 3-5mm below the head."
Have the first few "tapping thread" passed completely thru the plate when the screw breaks? Does the screw break more-or-less at the surface of the part?

RE: Trouble with Heat Treatment of 1022 steel Fasteners

If the size is right, and if the design is right, then the C control must be at fault.
Have you ended up with the material too hard too deep? Or is it too weak?
You need cross sections and microhardness traverse along with some analysis of the fractures.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Looking at information for these types of screws, generally the screws are limited to a maximum plate thickness equal to their diameter. It seems this is simply the wrong application for the screw. You may also have problems if the threads engage before the drilling tip has passed through the material.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

If the length of the drilling tip of the screw (not including the taper on the nose) is less than the thickness of the plate being drilled, your self tapping screw will never tap a hole through the plate without breaking - it's impossible.

When you're drilling, you're creating chips. As soon as the thread touches the top surface of the plate, the hole is closed. The chips have nowhere to go; they will jam the drilling operation and the shaft of the screw will fail. This will happen pretty much every single time unless the bit driving the screw becomes disengaged.

This seems to me to be an application of the wrong screw to the wrong plate, not a problem with the design or heat treatment of the screw itself.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

You'll first need to clarify what you mean by '1022' steel, because the first thing that comes to mind is SAE 1022, which in no way can approach 58-62 HRC, and isn't used for screws AFAIK.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Stupid mechanic here who works on automotive body-in-white, not a metallurgist. That looks like a wood screw or sheet-metal screw. There is no way you are going to self-tap 6mm of steel plate, even mild steel, with a screw like that.

Option 1 if you can get to the backside, a proper screw and hex nut with normal everyday M6x1.0 threads. No self-tapping no nothing. Drill a clearance hole, position the nut and screw, tighten, done.

Option 2 if you can't get to the backside, drill and tap a normal M6x1.0 hole and use a normal off-the-shelf M6 screw. Done.

Option 3 if you don't want to drill and tap, weld a weld-nut to the backside and use a normal off-the-shelf M6 screw. Done. We projection-weld weld nuts to the backside of sheet metal parts all the time. In my home shop, I've MIG-welded normal nuts to the backside of steel brackets many times.

Now, over to you. Wny won't these "standard off-the-shelf" solutions work for you?

Self-tapping screws are for sheet metal ductwork in a house. And I've never seen one that long.

I've seen self-tapping screws for ISO metric threads. https://www.mcmaster.com/self-tapping-screws/syste...

Those list use in softer materials ... but I've run across larger sizes of them used in automotive applications. I seem to recall one car that I owned, using M8-ish self-tappers holding the driver and passenger seats down to the floorpan.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

(OP)
Please advise Heat Treatment of this screw in a mesh belt furnace. Bulk.
Material is SAE 1022
C - 0.18 - 0.23
Mn - 0.7 - 1.0
P - 0.04 max
S - 0.05 max

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Industrial Fasteners Institute has some requirements for self-drilling tapping screws. Adapted from SAE apprently.
Design, torque testing, etc.

What is the plating on the screw?
What is your screws' minor diameter, and at what torque value to they break?
I'd be thinking if the torque required to tap exceeds the values in Table 3, the geometry of my screw or maybe even hydrogen embrittlement should be investigated.

RE: Trouble with Heat Treatment of 1022 steel Fasteners

Hi there
I have read it now, I am doing the heat treatment of self drilling screw the core and surface hardness with the same martial is about 400 Hv and 600 hv

please tell me your temper temperature ? I think you choose wrong temper temperature

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