How To Heat Treat A Knife With A Propane Torch? The 80 Top Answers

When used outdoors, a propane-oxygen torch reaches a maximum temperature of 3,623 degrees Fahrenheit or 1,995 degrees Celsius. Propane is a naturally occurring hydrocarbon, a component of natural gas or petroleum. In its natural state, propane is colorless and odorless, although a compound is added to create a detectable odor for leak detection. While the gas is often used for heating and cooking, propane-powered torches, used for thawing pipes or soldering plumbing, can also be found in many home workshops. In the kitchen, a propane torch can be used to caramelize food.

Propane burner temperature

Propane torches are best for small soldering or heating jobs due to their portability. While propane-oxygen combinations can reach a maximum temperature of 3,623 degrees F, or 1,995 degrees C, a propane-butane torch only goes up to 2237 degrees F, 1225 degrees C. A torch flame consists of two cones, an outer light blue flame and an inner dark blue flame. The hottest point in the flame is at the top of the inner flame.

propane blend

Bernzomatic warrants to the original purchaser that your LTR50, LTR100, LTR200 and LTR300 product will be free from defects in materials and workmanship for one year from the date of purchase. This warranty applies to all purchases of the LTR50, LTR100, LTR200, and LTR300 on or after June 1, 2016. This warranty does not apply to products that have been damaged by improper maintenance, accident, or other misuse, or that have become inoperable due to normal wear and tear. This warranty is void if the product is repaired or modified by anyone other than Bernzomatic.

Bernzomatic will repair the product if found to be defective in materials or workmanship. Instead of repairing a defective product, a replacement product can be delivered at Bernzomatic’s option. Bernzomatic’s sole obligation and your exclusive remedy under this warranty shall be limited to such repair or replacement.

To make a claim under this limited one-year warranty, contact a Bernzomatic dealer or Bernzomatic directly at 1-800-359-9678. A service employee will help you with this. When making a complaint, please provide proof of purchase.

Bernzomatic makes no other warranties with respect to the Product and limits any implied warranties to the duration of this Limited One Year Warranty. In no event shall Bernzomatic be liable for incidental or consequential damages. Some states do not allow limitations on how long an implied warranty lasts, or the exclusion or limitation of incidental or consequential damages, so the above limitation or exclusion may not apply.

This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.

Hardening is a method of making knife steel harder. By first heating the knife steel to 1050 to 1090 °C (1922 to 1994 °F) and then rapidly cooling (quenching) it, the knife steel becomes much harder but also more brittle.

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To reduce brittleness, the material is tempered, typically by heating at 175–350 °C (347–662 °F) for 2 hours, resulting in a hardness of 53–63 HRC and a good balance of sharpness retention and grindability and Toughness.

Tempering should be accomplished within a reasonable time after hardening, preferably within an hour or so. It is vitally important that the blade is allowed to cool to room temperature before tempering begins. Otherwise, the transformation into martensite will be interrupted and the hardening result may be impaired.

A higher tempering temperature results in a slightly softer material with higher toughness, while a lower tempering temperature results in a harder and slightly more brittle material, as shown in the figure below.

For example, a camping knife or survival knife can be hardened to 350°C (662°F) to withstand rough treatment without breaking. On the other hand, if the knife is expected to remain sharp, it can instead be tempered at 175°C (347°F) for maximum hardness.

Tempering temperatures below 175°C (347°F) should only be used in exceptional cases where extreme demands are placed on high hardness, since very low tempering temperatures result in a very brittle material. Likewise, tempering temperatures above 350°C (662°F) should be avoided as this can lead to brittleness and reduced corrosion resistance. Note that if the hardened blade is exposed to temperatures above the tempering temperature (e.g. when sharpening), the properties of the knife will be affected.

Properly performed hardening results in a good balance of hardness, toughness and corrosion resistance in the finished knife blade.

More details on hardening

Heat treatment of tool steel

It is important for anyone involved with heat treating tool steels to remember that there are no acceptable shortcuts in the heat treating process. Therefore, the use of best practices for preheating, austenitizing, quenching, deep cooling and tempering is mandatory.

preheat

Slow heating rates and appropriate preheating steps for tool steels offer several advantages. First, most tool steels are sensitive to thermal shock, and reducing thermal gradients created by rapid heating rates minimizes the tendency of tool steels to crack. In addition, tool steels undergo a volume change as they transform from their annealed microstructure to austenite while being heated to an elevated temperature. If this volume change occurs unevenly, it can result in unexpected distortion, especially in cases where there are differences in section sizes.

For most tool steels, choose a preheat temperature just below the material’s critical transformation temperature (Ac1) and hold it long enough to allow the entire cross-section to reach a uniform temperature. Further preheating and holding just above the critical temperature allows the material to change volume smoothly, resulting in less deformation. Preheating should be followed by rapid heating to austenitizing temperature.

austenitizing

The purpose of austenitizing is to allow carbide particles to partially or fully dissolve and diffuse into the matrix. Different types of carbides dissolve at different rates depending on the temperature, so the appropriate austenitizing temperature mainly depends on the chemical composition of the steel. In addition, the austenitizing temperature can be easily varied to tailor the resulting properties to specific applications.

In general, higher temperatures allow more alloy to diffuse, allowing for slightly higher hardness and strength. At lower temperatures, less alloy diffuses and the resulting matrix is ​​tougher and less brittle, although it may not develop as high a hardness.

Hold times at austenitizing temperature are usually extremely short – close to one to five minutes after the tool has reached temperature to avoid grain growth. Load thermocouples are often placed in parts or in representative cross-sections – the soak time is initiated once the center of the part has reached temperature. The optimum combination of properties is often achieved at the lowest cure temperature that produces adequate hardness for the intended application.

Scare off

After the alloy content has been redistributed during austenitizing, the steel must be cooled fast enough to transform to martensite. Most tool steels (Figure 5) actually develop a martensitic structure in the temperature range of 600°F (315°C) to 200°F (95°C). How quickly a tool steel needs to be cooled and what quenching medium it should be fully hardened in depends on its chemical composition. Higher alloy tool steels develop fully hardened properties with a slower quench rate. Typically, use the slowest quench rate appropriate to develop optimized part microstructure and hardness while minimizing distortion and risk of cracking.

Courtesy of The Yankee Corp., Fairfax, Vt., www.yankeereamer.com Figure 5. M-Series High Speed ​​Steel Reamers and Blanks

For the higher alloy tool steels processed above 2000°F (1095°C), the quench rate from approximately 1800°F (980°C) to below 1200°F (650°C) is critical for optimal heat treatment response and material hardness.

No matter how tool steels are quenched, the resulting martensitic structure is extremely brittle and highly stressed. If commissioned in this condition, there is a significant risk of tool failure. Some tool steels will spontaneously break in this condition, even if left untouched at room temperature. For this reason, once tool steels have been quenched by any method to a handling temperature of about 65°C (150°F), they should be immediately tempered, which is usually interpreted as within 15-30 minutes.

deep freezing

In most tool steels, retained austenite is highly undesirable because its subsequent transformation to martensite causes an increase in size (volume), creates internal stresses, and leads to premature failure in service. Retained austenite is transformed by deep freezing to -85 °C (-120 °F) or in some cases cryogenic cooling to -195 °C (-320 °F). The newly formed martensite resembles the original as-quenched structure and requires tempering. Deep freezing is often performed prior to tempering due to concerns about cracking, but sometimes between multiple temperings.

cranking

Tempering is performed to both stress relieve the brittle martensite formed during quenching and to reduce the amount of retained austenite present. Most steels have a fairly wide range of acceptable tempering temperatures. In general, use the highest tempering temperature that gives the tool the required hardness.

The rate of heating up and cooling down from the tempering temperature is not normally critical. The material should be allowed to cool below 65°C (150°F) and often fully to room temperature between and after tempering. A good rule of thumb is to soak an hour per inch of the thickest section after the entire tool has reached temperature, but definitely no less than two hours, regardless of size.

Multiple tempers are typical, particularly for many of the more complex tool steels (e.g. M-series and H-series) which require double or even triple tempering to fully transform retained austenite to martensite. These steels reach their maximum hardness after initial tempering and are referred to as secondary hardening steels. The purpose of the second or third temper is to reduce the hardness to the desired working level and to ensure that any new martensite formed as a result of austenite transformation during tempering is effectively tempered.

Other heat treatments

glow

Tool steels are normally supplied to customers in the annealed condition with typical hardness values ​​around 200-250 Brinell (≈ 20 HRC) to facilitate machining and other operations. This is particularly important for forged tools and die blocks where partial or full air hardening occurs, leading to residual stress build-up. Any dies and tools to be post-hardened must be annealed.

In full annealing, the steel is slowly and uniformly heated to a temperature above the upper critical temperature (Ac 3 ) and into the austenitic range and then held until complete homogenization occurs. Cooling after heating is carefully controlled at a specific rate as recommended by the steelmaker for the tool steel grade in question. Cooling normally continues to about 1000°F (540°C) when the steel can be removed from the furnace and air-cooled to room temperature.

normalization

The purpose of normalizing is to refine the grains and ensure that the microstructural components are evenly distributed throughout the matrix. Excessive segregation can lead to poor fracture toughness or deformation in tools, due in part to segregation and differential transformation rates.

Normalizing involves heating slowly to the normalizing temperature (i.e., in the austenitic range), holding at a temperature sufficient to allow homogenization to occur, and then cooling in air to room temperature. Caution is advised as many tool steel grades will air harden upon cooling from austenitizing temperatures.

Relaxation

In cases where tools have been subjected to aggressive machining, internal residual stress build-up must be removed. Stress relieving is performed at 925-1025°F (500-550°C), allowing the tools to cool to room temperature before heat treating. Stress relief built in as a preheat step is often used.

Common problems in heat treatment

decarburization

This can occur in all heat treating processes (even in vacuum furnaces if leaks are present) and is to be avoided (unless removed by machining) because of subsequent deterioration of the hardness of the finished tool. The use of vacuum or protective atmospheres minimizes or eliminates decarburization. Other techniques such as using a borax or glass coating have also been used.

resizing

The heat treating process results in an inevitable dimensional change – either an increase or decrease in dimension due to changes in the microstructure of the tool. A combination of variables often contributes, including high alloy content, improper preheating, long soak times, higher than necessary austenitizing temperatures, quenching variations, insufficient cooling between tempers, or other factors in the process.

Heat treatment processes are typically simple in process and application. But sometimes descriptions are insufficient because the same technique can be used to achieve different goals. The best example of this would be stress relieving and tempering. Both are performed with the same equipment and use the identical time/temperature cycles, however the goals for the two processes are inherently different. Against this background, the most important heat treatment processes are described below…

Classification of heat treatment processes

normalization

Normalizing steel allows the crystalline structure to be restored and restores the carbides to uniformity. Steel doesn’t like an uneven structure. If the carbides are agglomerated and oversized from forging, the steel will not hold as sharp as it possibly could. Bar stock from the mill should probably not need to be normalized, especially if it has been annealed. Forged material could probably benefit from this. Basically, heat it up in your forge or furnace and let it air cool. Finished.

glow

Generally, as the last heat of the day, most people heat up their forge to temperature, turn off the forge, and let the steel cool in the forge overnight. If you want to do other work you can use a half size trash can filled with vermiculite and heat a few large sticks of scrap steel to add bulk/heat. Heat the steel to temperature and place everything in the vermiculite to cool slowly, using the vermiculite as an insulator. Slower cooling in the forge works better, but boiling in the vermiculite works pretty well too. Some people prefer to use lime instead of vermiculite.

hardening

Generally in a forge, this means heating it until a magnet won’t stick, and then “just a little bit more” to get the extra heat into the steel, which isn’t magnetic. A few minutes at this temperature will not grow a grain but will allow the carbon to “go into solution”. Superheating steel into the 1550 F to 1600 F range and beyond and soaking it will cause grain to grow. Simple, heat it to non-magnetic, give it another minute or so to heat up a bit more, and extinguish.

Extinguish

Quenching oil is very demanding in design and application. If you can’t afford it, use low-viscosity motor oil, or even canola, vegetable, or peanut oil. It won’t be perfect, but it will work. Experienced knife makers will tell you to use special heat treatment quenching oil to get better results.

Most agree that the steel really needs to be cooled at high speed, like 1 to 2 seconds, and that is absolutely correct. However, that doesn’t mean you only have 1 second to get from your heat source to your quench. When a red-hot piece of steel is moved from heat to oil, many fires start. Knock the oil over, drop the red hot steel into the oil and fire immediately! So be careful! The steel retains heat and survives a few seconds in air when you switch from heat to deterrence. Do this safely and be prepared for a flare up of fire and a large amount of smoke. And always be prepared for a fire.

cranking

If you’ve done everything right with quenching, your steel will be as fragile as glass. If you drop it now, it will break. You want to temper it once it reaches room temperature. Temper twice for 2 hours each to allow the steel to cool back to room temperature between cycles.

450F gives about 62RC

500F gives about 59-60RC where most will want this steel.

600F gives about 58RC

cryo treatment

Cryogenic treatment involves soaking steel after hardening but before tempering at temperatures from at least minus -90°F (dry ice range) to minus -290°F (liquid nitrogen range) for eight hours. Most high carbon steels are not cryotreated as the benefit is not usually as significant for carbon steels as it is for the newer super stainless steels. Soak it overnight in liquid nitrogen or even in a cooler filled with dry ice. Some people add acetone to dry ice. Acetone is insanely flammable and it would not be a recommendation. Use kerosene or even diesel fuel if you feel you need a liquid medium, but simply placing your blade under a block of dry ice will do. Some opted for low-temperature heating at 300°F to 350°F, called a “snap temper,” to take some of the stress out of a hardened blade before cryo. Adding this step reduces the chance of the blade breaking.

Here is some information on heat treatment formulas for tool steels.

However, if you are looking for more detailed information on these processes and associated terminology, please read this guide: The Heat-Treating Data eBook published by SECO/WARICK Corporation.

Check out American Rotary’s 29-page Common Heat Treating “Recipes.” Find any type of steel and follow the heat treatment instructions to get the desired result! Click here.

Different Types of Quenching Oils for Blacksmithing 2022 (Compared)

The quenching process is a very important step in the forging process when working with heated metals. Quenching is a form of rapidly cooling a uniformly heated metal to limit and control the effects that slow cooling has on a metal’s microstructure and hence its metallurgical properties.

One of the common media in which a forging can be quenched is oil. There are many types of quenching oils to accomplish this task, but some may be better than others for specific applications.

The common quenching oils that we will discuss are motor oils, food grade oils, mineral oils, and automatic transmission oils, as well as commercial quenching oils. Although the properties of these oils can vary widely, it’s also important to consider their cost, availability, and compatibility with the grade and grade of steel you wish to quench.

1705 Shares Don’t forget to save this for future reference!

Selling AAA Quench Oil – 1 Gallon Jar Appearance: Light amber oil Viscosity @ 100°F: 14.0 – 19.3 cSt

Nickel Shot Time: 9-11 seconds Flash Point: >340°F

Parks AAA is considered a medium to medium speed oil. A quench oil is often described in seconds…

How do metal quenching oils work?

The quenching process consists of different steps. When a heated workpiece first comes into contact with the quenching oil, a vapor layer forms around the metal as it is fully submerged. This vapor layer is stabilized by various conditions.

The properties of the metal and the quenching oil can greatly affect the stability of the vapor blanket surrounding the workpiece. Once the vapor blanket is destabilized, nucleate boiling occurs. This step in the process has the fastest rate of heat transfer. When and how quickly this step takes place depends largely on the molecular composition of the respective quenching oil.

Once the process temperature falls below the boiling point of the oil, the process moves to the convection cooling step. The cooling rate in this step is highly dependent on the viscosity of the cooling oil, which in turn depends on its purity. Below is a great video showing the quenching process in two different media, both oil and water:

As previously mentioned, the properties of quenching oils can vary widely depending on the type of oil used. This variation affects the way the oil quenches a metal. Some of the effects it can cause manifest themselves as working metal structural changes that are more favorable at lower temperatures, such as phase transformations.

Phase transformations could increase the density of a metal’s crystal lattice, making it harder. A metal’s hardness can determine how pliable or brittle it is, making it an important property to control.

Is there actually a best quenching oil?

While there may not be one universally best quenching oil type, there are quenching oils that may be better suited for quenching certain types or grades of steel in a particular application than others. It is very important to consider this factor once you understand the properties of the metal you wish to quench.

Because quenching process conditions are not universal for all types of metal, it makes sense that the oils used for quenching should be selected based on properties unique to the particular steel or steel alloy being quenched.

Steels and alloys are quenched at different starting temperatures and cooling rates to promote the uniformity and quality of the end product. One of the most common combinations of metal and oil is mineral oils and oil hardened steels as they act as a medium strength deterrent.

Considerations when buying quenching oils

1) Oil quenching cost

The factor that is paramount when choosing a quenching oil for many forges is its cost. This is a very important and valid factor to consider as cost can be affected by the effectiveness of a particular oil in an application or simply by the availability of the oil.

If you are a beginner blacksmith just wanting to get started with some projects involving the quenching process in oil, it might be wiser to start with cheaper oils to practice and refine your technique.

If you are an experienced blacksmith trying to find the perfect quenching oil for your application regardless of cost, it would make more sense to select the ideal type of oil for your project – often in the form of commercial quenching oils.

2) Oil quenching rate and speed

The other physical properties of the quenching oil can also have a significant impact on how efficient it is at quenching a particular type of steel. Some metals require specific quenching rates to prevent cracking or distortion in their structure.

As briefly discussed, the viscosity of oil can speed up or slow down the convective heat transfer step in the quenching process, also known as the quench rate. The lower the viscosity of a given oil, the faster the heat transfer rate. It is also important to note that viscosity can also be affected by the degradation of the oil that occurs during use in the quenching process. This deterioration is characterized by the presence of oxidation by-products in the oil, which can also lead to an increase in the overall viscosity of the fluid and a decrease in the rate of heat transfer.

Another physical property that can affect quench rate is the water content of the oil. This property also affects the appearance and quality of the finished piece if it does not cause a fire in combination with the oil. Because water has very different properties from oil, more than two percent of the water content in a quenching oil could result in irregularities on the workpiece surface and a dangerous combination. This is a form of contamination that can greatly change the rate of heat transfer on different parts of the metal surface due to thermal gradients.

3) Environmental impact of oils

The environmental impact of a quenching oil is a very important factor to consider when choosing a quenching oil. Not only does this factor impact how you dispose of the oil, but how often you can reuse a quench oil and get the most out of your supplies.

For example, premium quenching oils can last for years before needing to be discarded. Oil filtration and circulation systems are currently used in commercial plants to optimize the use of quench oil due to the rising cost of oil and its proper disposal. The recyclability of quenching oils can reduce your carbon footprint. Some oils can even be recovered as biofuels, further optimizing their use.

Different Types of Blacksmith Quenching Oils (Comparison)

1) Motor oils

Valvoline Advanced Full Synthetic SAE 5W-30 Motor Oil 5 QT (Packaging May Vary) 40% more protection than industry standards with enhanced anti-wear additives that provide additional…

Resistance to oil degradation 10X better than industry standards with a combination of premium antioxidants…

25% better protection against deposits with additional engine cleaners

Motor oils are a common type of quenching oil used in both forging and blade forging applications. New and used engine oils can be used for quenching, both of which are widely available. New engine oil is usually cheaper to use than commercial quench oils.

Used motor oil is often free or easy to get, but it may contain some contaminants used in a vehicle. Unfortunately, both new and used motor oil contain additives that can release toxins when the hot metal workpiece comes into contact with the oil during the quenching process. These toxins typically give off an undesirable odor during quenching. It is always advisable to avoid inhaling these toxins and wear the proper protective equipment for your application.

Quenching with engine oil should be done in a room with adequate ventilation. Because of the impurities in motor oils, many blacksmiths who use it find that there is a thin dark film on their finished workpiece after quenching.

Pros Cons Can be cheap, new or used

Widely accessible

Commonly used in blade forging Used motor oil can contain many contaminants

Motor oils contain additives that release toxins during the quenching process

Toxins smell bad when quenched

Should only be used in a well-ventilated area

Smell of deterrent motor oil should never be inhaled

Contamination can cause stains on the workpiece

2) Food grade oils

#1 Best Seller Spectrum Naturals Refined Organic Canola Oil, 32 oz For all-purpose cooking

Refined for a neutral taste

Expeller Pressed organic rapeseed oil with omega 3 fatty acids

There are many food grade quenching oils that can be used in blacksmithing. These options include vegetable, peanut, and avocado oils. Some commonly used vegetable oils are canola, olive, and palm kernel. Vegetable oil is very cheap and comes from renewable sources. They are biodegradable and can even be recovered as biofuels. As a quenching oil, vegetable oils have better impact energy values. This property allows them to increase the toughness of the workpiece.

The trade-off with these types of oils is reduced hardness. Peanut oil and olive oil could also be used for similar applications, but they tend to be more expensive than traditional neutral oils.

Advantages Disadvantages Inexpensive to buy

Widespread

Renewable Resources

Recyclable

Promotes the toughness of the workpiece. The workpiece does not reach the same hardness values ​​as when quenching other types of oil

Some vegetable oils are more expensive than others

3) Mineral oils and automatic transmission fluids

Mineral oils and automatic transmission oils are suitable alternatives for motor oils. In fact, these types of oils do not contain the additives that engine quenching oils are known for in blacksmithing. If you don’t have access to mineral oils, another great alternative for them is baby oil, it just adds an extra scent.

Mineral oil quenchants are excellent for steels that require a fast quench rate and for oil-hardened steels. Mineral oils generally have greater cooling capacities for steel alloys. Their efficiency in the quenching process increases their overall costs.

The environmental compatibility of mineral oils is not very good because they are not biodegradable. When these oils are heated to very high temperatures, there is a chance for dangerous flavoring compounds to build up and release toxins into the air.

Advantages Disadvantages Alternative to engine oil

Baby oil is an alternative to mineral oil

Contains no additives. Non-biodegradable quenching oil

Relatively expensive oil

When mineral oils reach high temperatures, they can produce toxic flavorings

4) Commercially available quenching oils

Sale AAA Quench Oil – 1 Gallon Jug Appearance: Light amber oil Viscosity @ 100°F: 14.0 – 19.3 cSt

Nickel Shot Time: 9-11 seconds Flash Point: >340°F

Parks AAA is considered a medium to medium speed oil. A quench oil is often described in seconds…

As the name suggests, commercially available quenching oils are specially produced for the quenching process. There is a wide range of commercial quenching oils suitable for the different types of steel and steel alloys to be quenched. They are formulated so that various commercial quenching oils exhibit properties that can result in slow or fast quenching speeds.

Because commercial quench oils are made for quenching, they are typically the most expensive types of quench oil available. They are not readily available in general stores and have a higher cost than traditional oils.

If you are new to the art of blacksmithing or just curious about the practice, you may have heard of quenching or dipping your work piece in a substance to cool and harden it.

Blacksmiths generally use water, oil, or compressed air for quenching. These substances vary in terms of environmental impact, cost and impact on the metal, but the best quenching medium is usually water or quenching oil.

To learn more about what quenching is and which extinguishing agents are most effective, read on!

* This article may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases.

How does quenching work?

Quenching involves immersing hot metal parts in liquid or air. When workpieces reach the cooling process, quenching is used to speed up the cooling of the metal and increase its hardness.

Check out the video below from the Forged in Fire TV show for some great tips (PS: I love this show):

After the metal has been formed and soaked, it is immersed in a quenching liquid. When the metal is heated and reaches its proper temperature, it is soaked to keep its temperature even throughout the piece.

When the temperature is then constant, the metal is immersed in the quench material, creating a vapor layer around the metal.

This quenching process causes the metal’s crystal structure to decrease, making it denser, stronger, and harder.

Why is quenching important?

When steel or cast iron are made and slowly cooled, they form a weak metal.

The faster cooling of these substances allows for the formation of a much harder and stronger metal.

Therefore, by controlling the heat transfer from the hot metal you can ensure your metal is as strong as possible and improve its microstructure by preventing cracks and flaws.

Without quenching, your metal wouldn’t be hard enough to use.

Be sure to check the quenching performance of your steel before deciding which quench to use. This rating gives you information about which substance is most suitable for your material.

The most common substances used for quenching are water, quenching oil and air.

Different types of quenching media

The most popular types of quenching media for blacksmithing are quenching oils (vegetable, motor, mineral), water, and compressed air.

Read more about each one below:

1. Quench oil

Quenching oil increases wetting of steel during the quenching process, preventing cracking.

Oil quenching works best for knives, blades and some hand tools as these steels are generally designed for oil quenching. It also extinguishes faster than compressed air. Although it does not quench as quickly as water, it causes fewer cracks than water quenching.

Quenching oils are less efficient at quenching than water because they often form a sludge during quenching. Sludge and varnish are not evenly absorbed by the steel surface, so these by-products change the rate at which different parts of the steel surface cool.

This can reduce efficiency by allowing parts of the surface to cool more slowly and also less evenly, creating uneven heat transfer that in some cases can lead to warping and cracking.

The oil’s ability to properly quench the steel depends on the metal’s surface irregularities. Additionally, oils of different viscosities or thicknesses have different boiling and ignition points, so it’s important to consider thickness when deciding what type of oil to quench with.

Water content should also be considered when using quenching oil as water contamination in quenching oils can lead to increased cooling rate and spotting or cracking.

Certain types of quenching oils are better suited to different people depending on their financial situation, environmental concerns, and what you are welding. The most common quenching oils are motor oils, mineral oils, vegetable oils and commercial oils.

a. vegetable oil

If you want to use vegetable oil for quenching, coconut oil is a good option. Not only is it an effective quenching oil, it also leaves a great smell in your forge.

In general, vegetable oils are a good option for home smiths because they are widely available and easy to use.

One problem with coconut oil is its cost — it’s generally more expensive than other vegetable oils.

However, vegetable oils are the most household-friendly quenching oil due to their general availability and lack of additives.

b. Engine oil

Motor oil can be used for quenching without any problems. Even used motor oil can be used for quenching, so this is a great option if you have extra or want to save money.

Motor oil that has been used in a vehicle is readily available, or even free, but may contain contaminants because it is inside the vehicle.

In addition, motor oil can be dangerous or uncomfortable because it releases strong-smelling toxins and additives.

When quenching with engine oil, you should work in a well-ventilated area and wear protective clothing.

c. mineral oil

Mineral oil works just as well as motor oil, but doesn’t contain the same toxins or additives, making it a safer alternative.

It can be bought in bulk from Amazon, such as B. this mineral oil from Pure Organic Ingredients. However, it is more expensive than motor oil, which is often free.

Fortunately, you can use baby oil even if you don’t have access to mineral oil. Surprisingly, this oil works as a replacement for mineral oil when quenching metal!

If you are environmentally conscious, remember that these oils are non-biodegradable, so they have a negative impact on the environment and can release toxins at high temperatures.

i.e. Commercial quench oil

Commercially available quenching oils are oils specially produced for the quenching process.

These oils are specially made for different steels and alloys so you can be sure they are making high quality products.

While these oils are a great option for professional blacksmiths, they are typically more expensive than other oils.

2. water

Water can also be used to quench metals. It has a low viscosity (because it’s very thin) so it vaporizes quickly and quickly exchanges heat with the metal.

These properties allow water to cool metal faster than other quenching media.

While water makes metal significantly harder by quenching it, it can also make it brittle and prone to cracking.

This is a compromise of using water instead of oil, since water is more likely to crack the metal than oil.

To quench a workpiece in water, the workpiece is immersed in a water tank until the workpiece and the water are at room temperature.

Water is more sustainable than other extinguishing media as it has little impact on the environment.

Because water is easily accessible, it is also generally inexpensive.

3. compressed air

Compressed air is one of the less commonly used media for quenching. Exposing metal to air cooling to cool is technically “air quenching”. However, when the metal is immersed in compressed air, it cools faster than in normal air.

While this method is effective, it does not drastically change the structure of the metal or make it significantly harder.

Therefore, for stronger or harder tools, you may want to use an alternative medium. However, it is also less likely to cause cracks or brittleness in the metal, making it more flexible than other substances.

In general, compressed air is accessible and inexpensive.

Conclusion

In summary, blacksmiths use many media for quenching. The most common quench media are water, compressed air and quench oil.

Water and compressed air are the most sustainable and cost-effective quenching methods, but water can crack the fluid.

Compressed air can also be a less than desirable option because it cannot greatly affect the properties of metal.

Blacksmiths also use oils for quenching. While commercial quenching oil is the best quality and most specific oil, motor oil, mineral oil, and even vegetable oil can produce positive results when quenching.

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Is a propane torch hot enough to melt glass?

Nevertheless, there are specialized glasses that will melt at as low as 900 degrees. A kiln is necessary to raise the temperature of glass to 1400 to 1600 degrees, while a blow torch can raise the temperature of glass to approximately 900 degrees. Ignite the flame on your propane blow torch.

Could this be heat treated with a propane torch?

Heat treating with a Map Pro Torch

Heat treating with a Map Pro Torch

Heat treating with a Map Pro Torch

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See some more details on the topic how to heat treat a knife with a propane torch here:

Top 9 How To Heat Treat A Knife With A Propane Torch

1. How to Heat Treat a Knife | Red Label Abrasives · 2. Using Map Torches – Heat Treating 101 · 3. How to Harden Steel: 10 Steps (with Pictures) – wikiHow · 4. How …

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Source: thuvienhoidap.net

Date Published: 4/12/2022

View: 1803

Could this be heat treated with a propane torch?

Put it on a brick or something that will reflect the heat. Move it around a lot. The knife needs to stay at critical for 12-15 minutes. I use a …

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Source: bushcraftusa.com

Date Published: 11/7/2022

View: 9239

o1 heat treat with a propane torch – BladeForums.com

step 4 while first blade is in the oven, start heating blade 2 with torch, quench, put in oven next to blade one.

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Source: www.bladeforums.com

Date Published: 10/22/2021

View: 1723

Can you heat treat knives with a blow torch? – Quora

Reheat entire blade length (keep it moving) very gently above a soft low heat propane or alcohol lamp, or gas stove flame until a light yellow color is observed …

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Source: www.quora.com

Date Published: 11/27/2021

View: 945

Poor Man’s Heat Treating Thread… – KnifeDogs.com Forums

Hardening: Heat to 1475F to 1500F (steel type depending) until the metal is just past non-magnetic. Non-magnetic is around 1425F. A propane …

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Source: knifedogs.com

Date Published: 8/12/2022

View: 3759

unsuccsessful heat treat with torch. – Beginners Place

Using just a MAPP gas torch alone won’t quite do it. Even with an OA torch, it’s tuff to get an even heat on a blade. It can be done, but it …

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Source: www.bladesmithsforum.com

Date Published: 10/24/2022

View: 8381

practicality of heat treating with plumber’s propane torch

It’s easy to build a bean can forge with a propane plumbers torch. You need about 1 linear foot of ceramic wool insulation and a metal coffee …

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Source: www.iforgeiron.com

Date Published: 11/25/2021

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How to Flame Harden Steel

When flame hardening steel, the steel is heated and then cooled. This first part of the process changes the molecular structure of the steel, making it hard but brittle. If dropped or hit hard, it could actually shatter. The second part of the process, known as annealing, involves reheating and recooling the steel. After this second part of the process, the steel is hardened yet malleable enough to still be machined.

How to Heat Treat a Knife

Brief Summary Heat treating is a part of the knife manufacturing process designed to harden the steel of the blade for use. The heat treatment can be performed in four steps: normalizing, quenching, tempering and grinding.

Topics covered:

The purpose of heat treating a knife is to harden the steel enough for use. The correct degree of hardness depends on the intended use of the blade. It must be hard enough to retain its sharpness but flexible enough to withstand regular and sometimes intense use.

At Red Label Abrasives, we pride ourselves on providing knife makers with the sharpening kits they need to produce quality knives. In this blog we discuss the steps involved in heat treating your blade so that the finished product strikes the perfect balance of strength and flexibility. These steps can be applied to all common knife steels, including 1080, 1084, 1095, and 5160. The steps also work whether your knives are forged or worn.

what you will need

Knife blade beveled and surfaced to desired finish (once hardened, material is more difficult to remove by filing and sanding)

Heat source (e.g. propane torch, mini forge, or charcoal forge)

Refractory quench tank with lid. You can use metal coffee tins, a cookie jar, or something similar.

oil for quenching. Realistically, most types of oil will work for this. Don’t use water though – it cools too quickly and will crack most steels.

Fireproof regulator block, e.g. B. an aluminum tube to keep the blade at the correct depth in the quenching oil.

Magnet for checking steel temperature

Tongs or vise tongs to securely hold the blade during heating, quenching and tempering.

Fire extinguisher for grease or oil fires

Face shield and heat resistant gloves

File for testing blade hardness

kitchen stove (recommended)

Step 1: Normalize

With this step, you restore a uniform or normalized condition within the steel, making it stronger and easier to machine. The forging process in particular causes the carbides to bunch up and become oversized, which can prevent them from properly holding an edge.

Use a sheet of P150 grit sandpaper to dull the blade edge and minimize the possibility of warping or tearing during treatment. Then use the heat source to heat the steel to 1500~1600℉ before allowing it to cool. Be sure to turn it over the flame regularly: concentrating on one side can cause problems with the finished product.

Below you will find an overview of recommended heating temperatures for common knife steels:

1080:1500℉

1500℉ 1084:1500℉

1095:1575℉

5160: 1525℉

You can use a magnet to judge the temperature: steel loses its magnetic ability at around 1425℉, so if you heat it to a point where it’s not magnetic, you’ll know you’re close. Heat the steel a few shades lighter and you should be at the right heating point.

Another way to test the temperature is to put salt on the steel surface. Salt melts at 1474℉, so when you see it liquefy, you know you’ve reached the critical temperature.

Step 2: Quenching

After heating, quickly dip the steel in a can of oil and move it back and forth in a cutting motion. This will prevent air bubbles from forming around the steel. Then place it on the regulator block which should be submerged in the oil. (The block ensures that both sides of the blade are evenly cooled.)

Many knife makers recommend using canola oil heated to around 130°C, saying that water tends to cool the steel too quickly, which can cause cracking, especially if the blade is on the thin side. In comparison, oil has a slower cooling rate. You can heat it on your stove or use your forge to heat a piece of rebar before dipping it in the oil to raise the temperature.

In order for the blade to harden, it must cool below 900℉. Wait about 10 to 15 seconds before pulling out the blade and checking for warping. When it looks good, take a file and scrape the corner across the steel. A properly hardened blade is stronger than the file and resists scratches.

Step 3: Tempering

Blade steel is extremely brittle after quenching. To soften the steel and relieve any built-up stress, you must reheat it immediately—this time to 400℉. This process, known as tempering, can be done over a fire or with a blowtorch, but the simplest method is to place it in your oven at 400°C for two one-hour cycles, allowing the knife to cool between each cycle . If using another method, heat the knife until it turns a golden, straw-like color typical of 400℉.

Note:

Some knife makers treat their blades with a cryo treatment prior to hardening. The steel is soaked overnight in dry ice or liquid nitrogen at temperatures between -90℉ and -290℉ depending on the medium used.

Tempering temperatures below 347°F should only be used in certain circumstances, e.g. B. with extreme requirements for high hardness, as lower temperatures typically lead to a very brittle blade.

Tempering temperatures above 662°F should be avoided as they can cause reduced corrosion resistance and brittleness. If the treated blade is exposed to heat that is higher than the tempering temperature (e.g. when sharpening), the knife properties will be impaired.

Wrap up

By now your blade is fully hardened. Now all you have to do is grind off any lime that may have collected on top of the blade after quenching. Apply a fine abrasive to your belt sander and gently run it over the surface until the steel is clean. You can then complete the final steps of adding an additional bevel at the desired angle and using a fine grit for final sharpening and polishing.

For over 35 years, Red Label Abrasives has provided both hobby and professional knife makers with abrasive belts that achieve excellent results. We sell complete knifemaker’s kits as well as separate belts and blades to replenish your inventory.

Red Label Abrasives is a family business that has been manufacturing high-quality American-made abrasives for over 35 years. We take great pride in providing unmatched product quality and customer service. For more information about our products or to place an order, please call 844-824-1956 or fill out our contact form.

Could this be heat treated with a propane torch?

For this blade size, a propane torch should do the job. As mentioned, hold it in the heat until the steel is cherry red. I’ve heard that quenching in ice water is a good quick fix, but then I’m not a knife maker and have no idea about quenching materials and their properties.

My father was a tool and die maker and I watched him heat treat tools with an oxy-acetylene torch and oil quench. It worked, but then again, he knew what he was doing and I didn’t. He was very good at his job.

steve

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