Many people are surprised when they hear that aluminum can be annealed. Since it's already a soft material, why do you need to make it even softer?
In fact, not all types of aluminum can be annealed. It's just certain qualifications. In this article, I'll cover what qualities can be annealed, what you gain from annealing, and a great trick to get it right every time.
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How to shine correctly always at hand
It's best to start with what you're likely to be most interested in.
If you already know that the strain you're working with can be annealed, and it's worth doing, you can (almost) always anneal like this:
Get a Sharpie.
Yep, that stupid cheap permanent marker. You probably have 3 in your toolbox right now. It doesn't matter what kind, it doesn't even have to be a Sharpie brand (although I don't see why you wouldn't want to use it).
Scribble across the piece of aluminum. Don't worry about 100% coverage, just enough to leave a mark in any general area.
Now get your flashlight. Start heating the part. Don't heat up too quickly and keep the flame across the piece to keep the heat even. You don't want hotspots. It's actually quite easy to overheat and melt the material (the glow occurs at a temperature just one thread below the melting point), so be patient and take your time.
You will see the Sharpie marks change color. So, at a certain temperature, they practically disappear. That's the sweet spot you've been looking for. Cool the aluminum in water and voila!
The nice thing about this method is that it gives you multiple ways to heat aluminum depending on what you have. You can use an oxyacetylene torch, propane torch, or whatever you have on hand to bring the material to about 775 F. This is the ultimate DIY method for annealing aluminum.
If you're one of those rare people who doesn't have a Sharpie in your toolbox, there are other ways to achieve the same result:
- If you use an oxy-fuel torch, light it with very little oxygen. Then pass the smoked flame over the piece. He will cover it with black charcoal. Then turn on the oxygen in a normal amount and heat the part until the carbon runs out, just like Sharpie brands do.
- You can also use bar soap if needed. Simply rub dry onto the surface of the piece and heat until golden brown. Not my favorite approach, but it works. I don't know if all soap brands will do this, but I know Dove will do the job.
To be clear, this is not technically considered a full annealing. The complete annealing of aluminum requires highly controlled furnaces and specific waiting times. However, a partial annealing like this gives you the ability to more easily shape it without breaking it.
This technique also only works with sheet metal or very thin parts. The heat must penetrate through the metal. If the metal is very thick, the surface temperature will be adequate, but the core temperature will be too cold for annealing.
Note on carbon soot process:It takes a little skill to know how thickly to apply carbon black. The amount you need to apply depends on the thickness of the metal. If it's only about 0.020" thick, you'll need to coat it very lightly, not even completely black. Otherwise, the soot will take a long time to burn off and you'll end up melting the part. Try it a few times on a practice piece to get an idea.
If you are working with a thickness around 0.020″-0.030″, the soot should not be completely black. You should be able to easily see the metal underneath. If closer to 0.040″-0.060″ thick, carbon black should be applied to the surface to make it completely black.
Pro tip:If you really want to identify the temperatures, you can use special markers that range from opaque to transparent down to 1% of the desired temperature. Just search for "temperature sticks".
Applications where manual annealing works very well
There are some areas where annealing aluminum in this way makes a lot of sense. Here is a short list with some examples:
Rohr To bend:Aluminum tubing can be difficult to bend without cracking or at least turning white. Annealing them is a great way to have a tube that retains its strength.
Tube smoothing:If you're doing something structural with pipe, you can flatten the ends so you can drill through them to safely drive a screw. Glow is a great way to get a nice clean shape. I made a 2" diameter tube with a 1/16" wall, but I'm sure you could make it a little bigger. Annealing allows the face to be changed without unduly deforming the tube - the curves will be well defined.
Flat bar flex:I've done this quite successfully with a 1/2" x 4" flat bar. Bending flat bars can be tedious as it is.Yes reallyprone to cracking. I definitely recommend shooting for refurbishment whenever possible.
The good thing about torch glow is that it is very easy to locate. Just redo the section to be bent, without having to mess with the rest. Once formed, the bent areas will likely work hard and regain a good deal of their strength, and the parts you didn't anneal will remain intact.
How to Anneal Aluminum with a Heat Treat Furnace
Obviously this will depend a lot on the quality of the aluminum. That said, the basic process is generally the same. Heat it to a certain temperature, keep it at that temperature, and then cool it down. Once you've finished machining, it's fairly easy to restore the aluminum's temper with a little more heat treatment.
Here are some common types of aluminum you might want to heat treat, along with furnace annealing instructions:
| 1100 | Tempered to 650 F, make sure it's hot at all times, and let the air cool. |
| 2024 | If working in a heat-treated state, soak at 750 F for two hours, then cool slowly in the oven. Annealing at 650 for 2 hours between cold working and then air cooling. |
| 3003 | Quench at 775 F, fresh air. |
| 5052 | Temper to 650 F then air cool. |
| 6061 | Temper to 775 F, hold at temperature for 2-3 hours and allow to air cool. |
| 7075 | Annealing at 775 F for 3 hours, then quench to 500 F at a rate of 50 F per hour, then cool in air. This is a tricky thing to work with. |
Well, once you've annealed and worked with the aluminum, you might want to go back to the previous heat treatment. If not, you might be fine, or you might end up figuring something out later. It depends on the importance of the part you are working on.
I won't go into all the different ways to heat treat each grade of aluminum and how to get each temper easily would be a separate article. Since this is specifically about annealing, keep in mind that it may be worth restoring heat treatment and tempering to anything that has been annealed.
What does annealing do to aluminum?
Since aluminum is already such a soft material, what can be gained from annealing?
The main reason for annealing aluminum is to improve formability. Any associated deformation can cause cracking or material fatigue, but annealing can reduce these problems.
Quick Tip: Avoid machining aluminum during annealing; it is too sticky and will no longer cut cleanly. It will be more difficult to get a good surface finish that is not completely worn away. It is also very likely that the material will stick, fuse with your cutting tools and cause a catastrophic failure that everyone in the shop will know about. If possible, try to reheat annealed parts before machining.
If you bend non-cold-annealed aluminum, you'll likely see the drawn side turn slightly white. They are small cracks that form on the surface of the material.
It's usually not a big problem, but under certain conditions it can be a problem. For example, if it's a high-performance part that you need to rely on for maximum strength, cracking is a big problem. In applications where bent aluminum is exposed to vibration, additional tempering can be helpful. Or when exposed to heat/cold (even in summer and winter in northern areas).
As long as you are actually reshaping the metal, are trying to stretch it, shrink it, or draw it deep, you should at least remember to anneal it.
Note that you may need to anneal it several times when casting it, as the aluminum will harden and become rigid again. It can also fade over time - some classes only keep it for an hour, others can keep it for a year. Aluminum can be a fun thing once you get to know it.
What types of aluminum can be annealed?
Here is a list of forged grades and information on whether they are also suitable for annealing:
| 1xxx - Pure aluminum (99% or better), also known as electrical grade | Not heat treatable. Glowing is technically possible, but it is very difficult and should be avoided unless absolutely necessary. To be honest, this material is so soft that it's highly unlikely that you'll need to relieve it unless you're really stretching and squeezing it. |
| 2xxx - copper alloy | heat treatable. In general, however, this grade is prone to hot cracking, so do not attempt to anneal it unless absolutely necessary. |
| 3xxx – Manganlegierung | Not heat treatable. This is a very malleable material and is commonly used in applications such as cookware. You can cook it easily. |
| 4xxx - silicon alloy | Both heat treatable and non heat treatable depending on the digits after 4. It can have a silicon content of up to 21.5% making the melting point very low. It is often used as a soldering additive. The glare is a pain. |
| 5xxx - Magnesium Alloy | Not heat treatable. This is commonly seen in sheet form, and it is a pliable material. Gloss works well for deep and complex modeling, but you are unlikely to need it for simpler things. |
| 6xxx - Magnesium-silicon alloy | heat treatable. This is one of the more common grades of aluminum (particularly 6061) and it anneals very well. It may need to be annealed several times during molding as it tends to harden. |
| 7xxx - zinc alloy | heat treatable. This is a very rigid aluminum that is commonly used in aerospace applications for things like wing spars. Glitter is possible, but extremely difficult and should be avoided, especially if you are trying to do it by hand. It is also very prone to stress cracking. |
| 8xxx - "other elements" | This is a totally random mix of alloying elements and usually some very special stuff. On glitter, your guess is as good as mine. See if you can get information from the provider. |
Practical information about aluminum designations
Here is an explanation of some of the additional codes you will find in the grade designation to help you understand what condition the aluminum is currently in:
Basic designation of aluminum heat treatment:
| F | "As Manufactured": The material has not been controlled after the casting, hot stamping or cold stamping process. |
| o | "Annealed" - very low strength, but extremely ductile. |
| H | "Strain Hardened" - This only applies to forged products. This designation is followed by a number, which is explained in the table below. |
| C | "Heat-treated solution" - you almost never see this - is uncured and therefore unstable. Internal stresses are high and it is generally best to avoid this type if possible. |
| T | "Solution heat treated" - Improved by heat treatment, possibly work hardened, but a temper code (described below) explains what else can be done to adjust the properties of the aluminum. |
Aluminum tempering codes:
| T1 | After a high temperature forming process (such as extrusion) naturally cooled and aged to a stable condition |
| T2 | Chilled from a high temperature forming process, cold worked and naturally aged to a stable condition |
| T3 | Solution heat treated, cold worked and naturally aged to a stable condition |
| T4 | Heat-treated and naturally aged solution for stable condition |
| T5 | Chilled from a high temperature forming process and artificially aged |
| T6 | Artificially aged and annealed solution |
| T7 | Heat-treated and aged solution |
| P8 | Solution annealed, cold worked and then artificially aged |
| T9 | Solution heat treated, then artificially aged, then cold worked |
| T10 | Chilled in a high temperature forming process, cold worked and then artificially aged |
Deformation hardness codes for aluminum:
| H1 | hardened stress |
| H2 | Work hardened and then partially annealed |
| H3 | Work hardened and then stabilized |
| H4 | Work hardened and then painted or varnished |
Okay, that's all you need to know about glitter. I hope this helps.
Keep in mind that you may need to test the process a bit before you risk ruining something valuable. See if you can get a small piece of the exact aluminum you are working on to see exactly how it reacts.
Doubts? More tips? Write them in the comments!
FAQs
At what temperature does aluminum anneal? ›
To anneal a work hardened aluminum alloy, the metal must be heated to somewhere between 570°F to 770°F for a set amount of time, ranging from just thirty minutes to a full three hours. The time and temperature are depending on two things: the size of the part that is being annealed and the composition of its alloy.
Can you anneal aluminum with a propane torch? ›You can use an oxyacetylene torch, a propane torch, whatever's on hand that can get the material up to around 775 F. This is the ultimate DIY way of annealing aluminum.
What are the 3 stages of annealing? ›- Recovery stage.
- Recrystallization stage.
- Grain growth stage.
To date, the annealing process can be done through three primary stages. These stages are recovery, recrystallisation, and gain growth. The recovery stage of annealing recovers the physical properties of the metals.
What is the formula for annealing? ›The optimal annealing temperature (Ta Opt) for a given primer pair on a particular target can be calculated as follows: Ta Opt = 0.3 x (Tm of primer) + 0.7 x (Tm of product) – 14.9; where Tm of primer is the melting temperature of the less stable primer-template pair, and Tm of product is the melting temperature of the ...
What temperature do you anneal metal? ›Annealing is done at high temperatures, usually at about 1500 F for steels. Tempering is done at low temperatures, typically up to about 500 F. Typically tempering is done after a hardening process to relieve internal stresses and prevent future catastrophic failure.
Does annealing aluminum weaken it? ›investigated the organization and its properties of multi-pass cold-rolled aluminum sheets during graded annealing. Their results revealed that annealing at high temperatures weakens the strength of the texture and thus affects its mechanical properties.
How long should I anneal for? ›Alloys are annealed at temperatures of between 300-410°C, depending on the alloy, with heating times ranging from 0.5 to 3 hours, depending on the size of the workpiece and the type of alloy.
Do you quench after annealing? ›To anneal a metal you must bring it up to a critical temperature with a torch and then quench the hot metal in water. Be careful not to heat metals beyond the annealing temperature or they will melt.
What temperature does aluminum become pliable? ›Aluminum becomes soft and loses its strength at 160 ∘C
There are 3 stages of the selection process - Prelims, Mains and Interview. The prelims exam is scheduled on 17th December 2022.
How long does it take to anneal aluminum? ›
Annealing requires heating the alloy between 570°F to 770°F for thirty minutes to three hours, depending on the composition of the alloy and the size of the part.
Does propane burn hot enough to melt aluminum? ›Aluminum has a low melting point, so you can easily melt it using a propane torch or a DIY foundry.
Do you need to anneal aluminum? ›Aluminum may be fully or partially anneal aluminum, depending on the required mechanical properties of the finished product. Metals like aluminum are annealed because they're more likely to experience strain hardening.
What temperature is used for annealing? ›The temperature range for process annealing ranges from 260 °C (500 °F) to 760 °C (1400 °F), depending on the alloy in question. This process is mainly suited for low-carbon steel. The material is heated up to a temperature just below the lower critical temperature of steel.
What temperature is the annealing step? ›The annealing step (30 sec to 1 min, at temperatures 45–60 °C), is required so that the primers bind to the complementary sequence on each of the DNA single strands. The primers are designed such that they bracket the target of interest and the region of sequence that lies between them is referred to as the amplicon.
How is annealing done? ›annealing, treatment of a metal or alloy by heating to a predetermined temperature, holding for a certain time, and then cooling to room temperature to improve ductility and reduce brittleness.
What equipment do you need for annealing? ›What equipment is required for annealing? Most importantly, annealing requires a heating device to bring the metal to its required temperature. This is commonly a furnace, a type of high-temperature oven that is capable of reaching temperatures between 700 °C and 900 °C, although some can reach 1000 °C or higher.
What is the difference between full annealing and process annealing? ›Process annealing is carried out intermittently during the working of a piece of metal to restore ductility lost through repeated hammering or other working. Full annealing is done to give workability to such parts as forged blanks destined for use in the machine-tool industry.
What are the two types of annealing? ›The commonly used methods of Annealing are divided into two major categories, namely, annealing involving phase change crystallization above critical temperature and annealing below the critical temperature.
What happens if annealing temp is too high? ›Annealing temperature was too high
If the annealing temperature is too high, primers are unable to bind to the template. The rule of thumb is to use an annealing temperature that is 5°C lower than the Tm of the primer.
What solution is used in solution annealing? ›
ALUMINUM. Solution annealing is a high temperature heat treat process where the alloying elements of the material are brought into a solid solution. The solid solution condition is maintained by quenching the material in water or polymer.
Does annealing make metal harder or softer? ›Annealing involves heating steel to a specified temperature and then cooling at a very slow and controlled rate. Annealing is commonly used to: Soften a metal for cold working. Improve machinability.
Do I anneal before or after sizing? ›Should annealing be done before or after resizing? Annealing should always be done before resizing. This eliminates spring back, and ensures repeatable and accurate shoulder bumping and neck sizing. Annealing should be done every reload.
Does annealing metal make it stronger? ›The annealing treatment increases the system's strength by reducing dislocation emission sources and improves material ductility through strengthening grain boundaries' resistance to intergranular cracks.
Does annealing change thickness? ›The annealing process, which is believed as an efficient method to release the stress or leads to a thickness transition, turned the changing trend of refractive index back to normal. The stress in ALD-Al2O3 thin films caused the anomaly trend.
At what temperature does aluminum become weak? ›At temperatures above 150 °C, the alloy suffers a loss in strength with deterioration increasing over time. Above 200 °C, the weakening is substantial, and is accompanied by some gain in ductility.
Does annealing increase size? ›The final grain size depends on the annealing temperature and annealing time. For a particular annealing temperature, as the time at the temperature increases the grain size increases. For a particular annealing time, as the temperature increases the grain size increases.
How can I anneal at home? ›So how do you anneal steel? To anneal steel, heat it up about 100 degrees F above its critical temperature, soak it at that temp for 1 hour per inch of thickness, and let it cool at a maximum rate of 70 F per hour. Ok, that's the short answer.
What are the disadvantages of annealing? ›Disadvantages. The main drawback with annealing is that it can be a time consuming procedure, depending on which materials are being annealed. Materials with high temperature requirements can take a long time to cool sufficiently, especially if they are being left to cool naturally inside an annealing furnace.
How long should annealing be held? ›The annealing step (30 sec to 1 min, at temperatures 45–60 °C), is required so that the primers bind to the complementary sequence on each of the DNA single strands.