Hardening non hardened steel gears....??

[Whiplash]

Hello all! I have been away for a long time, but I wonder if anyone can help me with a small project I have going? I am making a gearbox for an electric bike I am building, but the gears I got are not hardened and after thinking about it, I am worried they will wear out quickly!  is there any simple method for slightly hardening gears? I am familiar with the old, heat em up and quench em in  oil trick, but I am worried if they will get distorted from this? if not then that will be fine for what I am doing, I just need wear resistance, they are decent steel....

Thanks all and I hope everyone is doing well!! We had our Baby Girl, Sydney, 7lbs 2 OZ. April 17th at 9:54AM and as you can figure, its been pretty busy!

[vidio1]

Congrats on the new addition. Usually the distortion comes from uneven heating....There is also carburizing compound. It may be easier/safer as nothing flashes fire. The process is called pack carburizing if you want to google it

[Whiplash]

Thanks! Its my first time with a baby and a gearbox design but I am trying to tackle both! LOL!

[fabr]

WHat is the alloy of the gears? You MUST know that first before the question can be answered.

[Whiplash]

They are 1144 steel, is this method OK to use? I have never done it before, but I figure it can't be that hard just to get them a bit better than they are now. I just don't want them to wear out really fast, since the motor turns about 6500 RPM the first stage of gears gets rung pretty good. The rest of them are fine I think, but I will harden them as well if the first one goes good. The box is 27:1 and will have a belt drive input to lessen harmonics from the motor and facilitate a nice clean form on the bike. Here is a very simple rendering of the layout minus the outer box itself and motor mount. Also here is a pic of the bike in its current configuration running 1200 watts using a chain primary drive into a 5:1 gearbox from a Chinese pit bike. The gearbox is the weak link, as I have already broke one of them, I am trying to make my own to replace both chain drive and gearbox so I can up the power to the 3500 watts the motor will take. The bike still does 40MPH and in first gear will climb ANYTHING you point it at until it flips over! REALLY good fun in areas that don't allow dirt bikes, which out here is everywhere! LOL! Once I get the box sorted out, I will be selling these bikes to the public. I have a website from my brother ready that will handle E commerce and everything. I am hoping these babies take off a bit, there is nothing like it out there for the money I am going to ask!!

I had just returned from the trail in the background. You can see a small hut at the top where i was minutes before. I didn't pedal even once....

[Hammerworks]

Do some research on "Kasenite".Its used for case hardening and is easy to buy and use.
I'm pretty sure it will work on stressproof but not 100%.
Heat the part with a torch.
Jam it in the can of kasenite until it cools.
Wire wheel to polish a bit.(dont touch with your bare skin at this point)
Reheat and quench in clean water.

[Doug Heim]

I dont think you would want to carburize 1144 as it already has alot of carbon in it and if you do so it will make the surface brittle. 1144 is a good strong material and can be heat treated to make it hard and wear resistant. I personally dont do heat treating my self, I send it all out, buy I am familiar with some of the processes... Faber is the voo doo heat treater and has done a ton of research. There is a thread on it somewhere. However from what I know... the last 2 #s are whats important for what process is to be used. Therefor, 1144 would use a similar process as treating 4140, 1045, 4340, 4150 and so on. I wish they were 8620, then a simple carburize would make them very hard and strong.

[fabr]

You guys really need to know what you are talking about before giving advise.


 
Applications & Process
Expert Tip
 
 

Heat Treating: Estimating Cost Savings
Many steel bar users have switched to Dura-Bar because it machines faster than steel. In fact, the free machining properties that allow it to machine at faster speeds than most steels have earned it the name "The Steel Alternative."

However, often overlooked, is Dura-Bar's significant cost advantage over some grades of steel requiring carburizing of parts prior to through hardening. When the low-carbon content of steel grades is too low, parts must first be carburized before heat treating in order to increase their hardness and strength.

Carburization takes time, as much as 13 hours to achieve a 0.030" case depth on a resulfurized steel. As every manufacturer knows, whether machining or heat treating parts, time is money. Because Dura-Bar does not need to be carburized, a lot of time, and money, is saved - on top of the machining advantage. This technical brief outlines a method for estimating the cost savings of Dura-Bar in heat treat situations.

Key Points


Ferrous metals cannot be hardened by heat-treating unless at least 0.35% carbon is present.
Low carbon steels such as 8620, 1212, 1117 and 1018 do not have enough carbon to respond to heat treating without first carburizing.
Carburizing steel can be a lengthy and costly process.
All grades of Dura-Bar ductile iron already have plenty of carbon available for heat-treating.
Simple assumptions can be used to estimate heat treating cost savings.
Recently a customer saved over $300,000 per year by switching to Dura-Bar - on just one part!
 

The simple guidline for estimating cost savings that can result from increasing machining speeds is:

75% x the % increase in turning speed = % decrease in cycle time

or

A doubling of the roughing speed will result in 1.5 times more pieces/hour

This formula has been useful in quantifying expected cost reduction through machining at higher speeds using Dura-Bar ductile over carbon steel.

Recently, we have seen an increase in new projects involving heat-treated steel parts. In most cases this means the conversion to a ductile iron part will involve heat treating to meet the application requirements. Depending on the grade of steel being used, the customer might realize significant savings in heat-treating by switching to Dura-Bar and it is important to recognize when such a situations exists and to estimate the savings by switching to Dura-Bar.

Here is one very important thing to remember when heat treating Dura-Bar:

Ferrous metals cannot be hardened by heat-treating unless at least 0.35% carbon is present.

What does that mean?

Low carbon steels such as 8620, 1212, 1117, 1018 will not respond to heat-treating simply because there is not enough carbon present.

How do you know if the steel grade in question has enough carbon? It's easy; the last two digits of the steel grade represent the carbon content in 1/100%. For example, 1212 has 0.12% carbon. The four grades above have less than 0.35% carbon. (8620 = 0.20%; 1212 = 0.12%; 1117 = 0.17%; 1018 = 0.18%)

By comparison, 1045, 4140, 1144, 1141 all have enough carbon and they can be hardened with conventional methods. (1045 = 0.45%; 4140 = 0.40%; 1144 = 0.44%; 1141 = 0.41%)


 

 
 
 

[Whiplash]

Ok cool, so I can use the simple oil quench method? how do I know when its hot enough? glowing? I heard you can stick a magnet to it and when it does not stick you are good, is that right? Do I need to water quench it after? How hot then?

THAANKS!!

[fabr]

Heat to nonmagnetic and oil quench.

[fabr]

FYI,make sure you have PLENTY of old oil to quench in. Probably a minimum of a couple quarts for a gear. You really ought to have a fire extinguisher at hand also.

[Whiplash]

OK great, is it OK to use fresh oil? I don't have any clean used oil, its all mixed up with other junk? Also they seem to be black oxide coated, is it still OK to just heat and quench? Thanks! I knew I could count on you Fabr!

[fabr]

Heat to non magnetic,quench in almost any  oil -new or used. I use tranny fluid.  Don't worry about the black coating.

[Hammerworks]

I personally wouldnt mess with 1144 too much ,you'll lose the toughness if you do it wrong.Thats why I recomended kasenit,few thou for wear resistance.

Dirty oil has the carbon it in.Reheat to a "straw" color then quench in water.This is where it gets tricky.You have to really watch the color or you'll make it too brittle.

[fabr]