How to harden stainless steel at home: instructions and safety precautions

When working with metal, people often wonder how to harden stainless steel. There are several ways. Metal hardening is a laborious procedure. It is necessary so that the products are strong.

Currently used industrial hardening of metal. It is produced in special thermal furnaces. Many are interested in how to harden stainless steel at home. It is difficult to do without special equipment. At home, you can make stainless steel more rigid and remove softness. In today's article, we will look at how to achieve this.

Why is this needed?

Before tempering a stainless steel, you need to understand what this procedure is for. If the steel is hardened correctly, it will not bend easily. After heat treatment, the product will not crumble.

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It is important not to overdo it with hardening, otherwise the metal will become very brittle. In this case, you have to spend a vacation product. Many do not know how to harden a knife so that the blade is strong and does not bend when cutting. This type of work is permissible to carry out at home, if you follow the safety rules. It must be remembered that steel cannot be overheated. If it becomes too hard, the knife will not cut well.

There are two options: temper the whole product, or only part of it. The first option is called global metal hardening, and the second - local.

General sequence of work

To properly harden a stainless steel knife, you need:

  1. Heat the metal part of the product. The handle does not need to be heated.
  2. Wait until the knife turns scarlet. The metal should heat up evenly.
  3. You need to warm the blade for no more than 10 minutes, after which it is placed in sealing wax and immediately removed.
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After work, you need to remove the remains of sealing wax from the blade. Next, wipe the surface with turpentine.

What will be required to work with stainless steel?

It is necessary to prepare the necessary materials in advance and take care of good equipment. If the house does not have an electric furnace, then an ordinary gas burner is suitable for the operation. You need to purchase sealing wax, as well as turpentine.

How does metal change during the course of work?

Many make blanks for knives at home. This work requires certain skills. Before you harden the knife at home, you should find out how the process goes and what happens to the metal.

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In the course of work, steel becomes hot. Depending on the material from which the sheet is made, it acquires a red or white hue. In the process of hardening, the metal becomes stronger than it was before the procedure. Strength increases in the following cases:

  1. When the alloy is heated to a certain point. The process of destruction of the crystal structure begins.
  2. The metal is transformed into a soft mass. Crystals acquire mobility. They turn into fine-grained. After the product cools, the grains do not lose their structure. A strong bond appears between them. As a result, steel becomes strong, but at the same time brittle.
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Many are interested in how to harden a knife. Experts advise working only with a cutting edge. In this case, the product will last a long time.

Hardness Test Method

Many people use a stainless steel knife in everyday life. If they do not know whether he needs heat treatment to increase wear resistance, they look at the degree of hardness of the metal.

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What it is? The hardness of a metal is usually understood as its resistance to loads from strong objects. There is a special Rockwell technique. It consists in pressing a ball of steel. Durable balls and diamond cones with an angle at the apex of 120 ° with a rounded sharp end are used as indenters.

Because of its simplicity, this method is one of the most common material testing methods.

How to determine the degree of hardness of a metal without special tools?

At home, without a device, you can determine the degree of hardness of the product. To do this, stock up on the file. It can be used to determine the hardness of a flat surface. This method also works with rounded surfaces. If the edge of the product is very sharp, a piece of glass is taken to test the strength.

If the metal is soft, then it will not cut the glass (maximum will leave a couple of scratches). When the metal is solid, it is difficult to take it with a file. After some effort, it may leave a noticeable mark on the glass.

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If the metal was subjected to strong hardening, then it is almost impossible to take a file. The product easily cuts glass. In the process you can hear a specific crunch.

What types of home training stand out?

Before hardening a stainless steel, you should find out what methods are available for working at home. Much depends on the correct task. It is important to consider what steel grade the stainless steel has. There are various modes of metal hardening:

  1. Hardening in a single environment. It is considered one of the simplest methods. It must be remembered that the method is not suitable for a metal that contains a lot of carbon. If you take a sheet of this type, then as a result of hardening, cracks will appear on it. The product becomes brittle and in most cases loses its shape. The method is excellent for products with a low percentage of carbon.
  2. Intermittent quenching method. It takes place in two stages. The product is cooled in water, after which it is placed in oil. You can leave the metal in the air. This method is suitable for high carbon metal. It allows you to harden steel without cracking. The method is considered difficult to perform at home. It should be used for products with a high carbon content.
  3. To harden a stainless steel in stages, it is first necessary to heat the metal, and then lower it into hot water with the addition of salt. The product is kept in a salt bath for up to 5 minutes. Gradual cooling occurs. The product is not affected by thermal stress. The advantage of this method is that it avoids cracks and other damage to the metal. The final stage consists in cooling the sheet in fresh air. This method is intended for thin metal, which contains a lot of carbon.
  4. Surface hardening of metal. It is often referred to as partial. Many people want to figure out how to harden stainless steel according to this method. In this case, you can see that the products receive surface strength. The core of the metal remains plastic. The method is perfect for hardening parts that can withstand heavy loads.
  5. The method of subsequent leave. It is interesting in that you can set the hardness of the metal to the desired depth. This method is used when working on percussion instruments. The strength of such products is increasing.
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What is used to cool stainless steel at home?

At home, for cooling after metal hardening, use:

  1. Water. She quickly copes with the function of a metal cooler. It is not recommended to place metal in water in which a high percentage of carbon is present. The product may become deformed. This medium is suitable for low carbon stainless steel.
  2. If a person wants to cool the product evenly after hardening, then he will need mineral oil. It allows the metal to cool slowly and does not cause deformation. This method is great for alloy steel.
  3. Sodium chloride or hydroxide present in aqueous solution. The concentration of the substance should not exceed 10 percent. The metal product will cool evenly. The desired method is applied to steel with a high carbon content.
  4. Various polymer solutions. These include detergents. The method is good in that it does not cause deformation of the material. There will be no defects on the product.

Table of metal cooling temperature after quenching

Recommended quenched metal cooling medium

Suitable temperature


20 to 80 degrees


20 to 200 degrees

Saline solutions

From 20 degrees and above to infinity

What you need to know to conduct the hardening procedure of stainless steel at home?

Before carrying out this operation at home, you should find out some rules:

  1. If the metal has an increased hardness, then it must be heated as much as possible. It is best to wait until the product is crimson.
  2. If a large amount of carbon is noted in the composition of the steel, then care should be taken to the cooling process.
  3. If the product requires hardening over the entire surface, then it should be evenly heated on each side.
  4. Do not overheat the stainless steel. Stains should not appear on the surface as a result of glowing.
  5. Before starting work, it is necessary to prepare special forceps. A capacity will be required to cool the metal.

Expert Advice

Specialists advise hardening stainless steel on an open fire. The fire of a bonfire is best suited for these purposes. Ready-to-use coals are recommended. They hold the desired temperature for quite some time.

If the product requires partial hardening, a blowtorch should be used. It is suitable for working with cutting edges and other small parts. It is important not to overdo the parts on fire.

Beginners often ask how to harden a stainless steel according to the instructions. It is also important to know what safety precautions should be followed when working with it. If the cooling step takes place using oil, it is necessary to keep a distance from the tank so as not to get burns.

How to reduce the hardness of a stainless steel using tempering?

Vacation is used to eliminate the increased hardness of the metal. The product is heated to a maximum temperature, and then gradually cooled in air.

For vacation you can use temperatures not exceeding the mark of 250 degrees. In this case, the material does not lose its strength. In this mode, they work with knives and other piercing objects.

Springs and spirals are recommended to be heated to 500 degrees. If a person works on parts intended for shock loads, then he can use the temperature regime from 500 to 700 degrees.

How to harden stainless steel? Safety precautions

To work with metal does not harm human health, the following safety precautions must be observed:

  1. Ventilate the room in which the metal is quenched regularly. It is recommended to install a special range hood in the room. Children and animals should not be allowed into the room where the work takes place.
  2. In the process you need to use special gloves. As soon as the instruments begin to glow, they are immersed in water until completely cooled.
  3. When working with fire, fire regulations must be observed, do not approach fire with flammable liquids.
  4. If the product is quenched in oil, the container is tightly closed with a lid.
  5. You need to work in special protective clothing. Sleeves and legs should be closed, as there is a risk of burns to the limbs.

So, we looked at how to harden a stainless steel. As you can see, this operation can be done with your own hands at home. The main thing is not to forget about safety and follow the instructions exactly.


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