2090 – 11 – Using Quenching

When manufacturers quickly cool metal seconds after it’s been soaked at an extreme temperature, it is called quenching. When metal is cooled so fast, the crystal structure of austenite, or F-C-C, doesn’t have time to form as it moves into the crystal structure of the ferrite, or BCC, phase. Instead, it forms the B-C-T crystal structure of martensite.
Quenching typically strengthens and hardens steel. It can be performed using a wide variety of liquids, like fresh water, saltwater, or different oils. Oil cools the metal much slower than saltwater, which cools quickest. The faster the metal cools, the harder the steel will be. But quick cooling goes hand-in-hand with the possibility of distortions being formed in the metal.

  1. List the effects of water vs oil quenching.

    • Water                          Oil

      Hardness

      Brittleness

      Straightness

      Place + or – on the correct side of each effect.

2090 – 01 – Defining Heat Treatment

2090 – 01 – Defining Heat Treatment

When metals undergo heat treatment, they are carefully heated and cooled in order to change their crystal structure, and therefore, their mechanical characteristics.Manufacturers don’t have the ability to control whether a change in crystal structures will occur; all heated metal will undergo a change in some way. Instead, manufacturers regulate the temperature, choosing only the right time to heat the metal.When done correctly, these heat treatments will enhance a metal’s properties. Standard treatments performed in workshops are softening or hardening, improving toughness or ductility, and relieving stress developing in the metal.

2090 – 02 – Knowing the Phases of Steel

2090 – 02 – Knowing the Phases of Steel

When metal begins to fluctuate in temperature, it passes through certain phases. These phases are defined by specific crystal structure formations. At room temperature, the steel has a body-centered cubic (B-C-C) crystal structure. This is the ferrite phase. Once the steel’s temperature rises to one thousand three hundred and forty degrees Fahrenheit, though, it enters its austenite phase, during which the steel takes on a face-centered cubic (F-C-C) structure.One of the main differences between the two phases is how much carbon each phrase can hold. Ferrite steel can only hold 0.02% carbon, while austenite steel can hold up to 2.11% […]

2090 – 03 – Understanding the Effects of Carbon Content

2090 – 03 – Understanding the Effects of Carbon Content

Steel in the ferrite phase isn’t able to hold as much carbon in the austenite phase. At the start of manufacturing, steel is in the austenite region at higher temperatures. At an elevated temperature, solid steel that has less than 2.11% carbon is able to retain carbon — even in a dissolved state. Austenite steel’s crystal structure has gaps that store carbon.FCC structure changes to BCC structure when the steel eventually cools down. The ferrite steel’s BCC crystal structure has fewer gaps that can store carbon. And so, when the temperature increases, the carbon that was stored in the crystal […]

2090 – 04 – What are Hypoeutectoid and Hypereutectoid Steels?

2090 – 04 – What are Hypoeutectoid and Hypereutectoid Steels?

Knowing how carbon precipitates is vital in understanding how steel will react at various temperatures and phases. The austenite phase has 0% carbon. As more carbon is introduced, the temperature of phase transformation lowers. Once the threshold of 0.77% carbon is reached, temperature climbs along with carbon content. At 1340 degrees Fahrenheit, steel reaches the eutectoid temperature, which is the lowest temperature that can change austenite into ferrite and cementite.Steel is then separated into two separate groups:– Hypoeutectoid steels have a carbon content of under 0.77%– Hypereutectoid steels which has more than 0.77% carbon content.These two types of steels have […]

2090 – 05 – When Does Pearlite Form?

2090 – 05 – When Does Pearlite Form?

At room temperature, steel contains both ferrite and cementite. As steel cools from the cementite to the austenite phase, part of the ferrite and cementite turns into pearlite. Pearlite has equal rows of ferrite and cementite. Austenite will become pearlite in between 1000 and 1341 degrees Fahrenheit.Pearlite formation occurs differently in hypoeutectoid and hypereutectoid steels. Since hypoeutectoid steel has less carbon, it forms ferrite first. The rest of the austenite will change to pearlite when temperatures are below 1341 Fahrenheit. This creates steel with a mix of ferrite and pearlite.Hypereutectoid steels have more carbon content, so cementite makes at austenite […]

2090 – 06 – Creating Bainite

2090 – 06 – Creating Bainite

Sometimes, manufacturers will speed up the heat treatments in order to affect the properties of a metal and the phases it goes through.When heated above the austenite phase, and then quickly cooled, before undergoing another, slower cool, steel will form bainite. It occurs when steel reaches between 420 and 1000 degrees Fahrenheit.Bainite is similar to pearlite in make-up: They both have a ferrite and cementite phase. Bainite has pieces of cementite that form in narrow and pointed patterns, or in sheets. Pearlite, on the other hand, looks like fingerprints. Bainite is comparable to pearlite in ductility, but is much stronger.

2090 – 07 – Creating Martensite

2090 – 07 – Creating Martensite

Once steel has been heated above the austenite phase and rapidly cooled back down to room temperature, it enters martensite phase. Quick cooling means carbon can’t precipitate from the steel. That’s why Martensite has no ferrite or cementite. Carbon gets stuck in the crystal structure even as the FCC structure changes to a BCC crystal structure. This causes the BCC structure to distort, creating a structure named a body-centered tetragonal structure. As heat escapes from steel in the Martensite phase, the steel expands a little bit. This type of stress can crack or distort the metal unless cooled the correct […]

2090 – 08 – The Process of Annealing

2090 – 08 – The Process of Annealing

Steel can be heat-treated to make pearlite, bainite, or martensite depending on the job. Annealing is one way that manufacturers control the temperature of the metal. It heats steel up to a specific temperature and maintains it that temperature for the appropriate amount of time. Then, the steel is cooled until the desired process is finished.Soaking is the process of keeping a metal’s temperature at an elevated temperature. Usually, steel is kept in a furnace and allowed to cool off for at least a day.A metal is annealed for a many different reasons. It can soften the metal and remedy […]

2090 – 09 – The Different Processes of Annealing

2090 – 09 – The Different Processes of Annealing

Manufacturers use different types of annealing to achieve greater hardness and decrease ductility. Annealing is an umbrella term for a few different processes a metal can be put through, but all annealing processes have some basic similarities. The four most common types of annealing are;• The full annealing process raises a metal’s temperature past the austenite phase, and then cools it slowly. It’s used to achieve greater ductility in low-carbon and medium-carbon steels.• The process annealing procedure is used to get rid of strain hardening in low-carbon steels before cold working.• The Recovery annealing process gives metals all the effects […]

2090 – 10 – Understanding Normalizing

2090 – 10 – Understanding Normalizing

Annealing and normalizing share procedural similarities. They both require metal to produce austenite, but their processes begin to differ as metal cools. Normalizing is much faster paced than annealing. Manufacturers achieve this pace by keeping the metal in open air at room temperature. Because this process occurs so much more quickly, normalized metal has distinct surface and interior characteristics.Normalizing creates a finer pearlite when compared to annealing which can be stronger, harder, and less ductile but more difficult to machine. Picking annealing or normalizing is dependent on the properties needed for the steel.

2090 – 12 – Tempering Martensite

2090 – 12 – Tempering Martensite

Martensite is quite hard but brittle, so it needs to be tempered to get better ductility and alleviate the stress induced during quenching. Martensite is the only metal that needs to be tempered, a process during which manufacturers soak the metal at the lowest temperature, ensuring that it does not return to its austenite phase.Tempering transforms some of the carbon trapped in the distorted crystal structure into cementite. While martensite loses some strength and hardness when tempered, it has much better ductility and toughness.

2090 – 13 – Combination of Heat Treatment Steps

2090 – 13 – Combination of Heat Treatment Steps

There’s nothing wrong with performing more than one heat treatment on your metal. When you buy treated steel, you buy it based on how it’s been heat-treated and the hardness that the heat treatments have created.A metal might go through many different processes, like keeping it at a high temperature and then slowly cooling it. Once the part is cold worked, manufacturers may use an annealing process to increase the metal’s ductility and allow for more cold working. Once the part has been shaped, a recovery anneal can improve toughness and achieve a manufacturer’s desired hardness.Two heat treatments are required […]

2090 – 14 – Understanding Hardenability

2090 – 14 – Understanding Hardenability

Some metals don’t handle heat treatment as well as others. The measurement of a metal’s ability to be hardened by heat treatment is called hardenability. The better the hardenability of steel, the easier it hardens below its surface without requiring drastic cooling.Hardenability is not the same as hardness, which is mostly attributed to carbon content. The higher the percentage of carbon, the more hardness a metal has. The more hardness steel has, the more difficult it is to get through its surface. Hardenability, though, represents how easy it is to get maximum hardness of a metal. The better the hardenability […]

2090 – 15 – Knowing the Types of Furnaces

2090 – 15 – Knowing the Types of Furnaces

There are a few different furnaces used to treat metals. Typically a furnace will be one of two types; batch furnaces and continuous furnaces. Batch furnaces keep the workpiece still during its heat treatment. Continuous furnaces rotate the piece while its being worked and its used more often because of its superior production rates and much better control over the heat treatment.A mixture of natural gas or propane with diesel or fuel oil is used to treat the metal. Typically a commercial furnace will facilitate a special atmosphere to heat treat the metal. This reduces any scaling that could happen […]

2090 – 16 – Utilizing Surface Hardening

2090 – 16 – Utilizing Surface Hardening

A metal may only have its surface hardened producing a tight grain structure. Surface hardening processes produce a metal that is ductile and tough on the interior and hardened, wear-resistant surface by heating the surface selectively.Induction hardening has an electrical current harden the surface. Flame hardening uses an intense flame then quenches the surface.If you change the chemistry of the surface, you can also change the properties:Carburizing will raise the temperature of a metal in an area that is carbon-rich creating a surface with high-carbon. Nitriding heats an alloy that has aluminum or chromium in an area that is based […]

2090 – 17 – Lesson Summary

2090 – 17 – Lesson Summary

Temperature and carbon content factor into the creation of steel phases. Steel exists in the ferrite phase at room temperature. Austenite phase is achieved at a higher temperature. Austenite has a higher capacity for carbon than ferrite. Once cooled, austenite will turn into a mixture of ferrite and cementite at a steady rate. Pearlite is a mix of ferrite and cementite, which is produced after a steady cooling rate. It is first rapidly cooled and then it is cooled afterward very slowly so bainite will develop. Martensite is steel that is cooled quickly. Annealing soaks a metal and then steadily […]

This is an error message

Updating...