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 in order for the products to be strong.
Currently, industrial metal hardening is used. It is produced in special thermal ovens. Many are interested in how to harden stainless steel at home. This 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, it is necessary to understand why this procedure is necessary. If the steel is properly hardened, it will not bend easily. After heat treatment, the product will not crumble.
Important notoverdo it with hardening, otherwise the metal will become very brittle. In this case, you will have to release the 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 can be done at home if you follow the safety rules. It must be remembered that steel must not be overheated. If it becomes too hard, the knife will not cut well.
There are two options: the whole product is hardened, or only part of it. The first option is called global hardening of the metal, and the second is called local.
General workflow
To properly harden a stainless steel knife, you need:
- Heat the metal part of the product. The handle does not need to be heated.
- Wait until the knife turns scarlet. The metal should heat up evenly.
- It is necessary to heat the blade for no more than 10 minutes, after that it is placed in sealing wax and immediately removed.
After work, you need to remove the remnants of sealing wax from the blade. Next, wipe the surface with turpentine.
What do you need 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 oven, then a conventional gas burner is suitable for the operation. You need to purchase sealing wax, as well as turpentine.
How does metal change during work?
Many people make blanks for knives at home. This job requires certain skills. Before you harden a knife at home, you should find out how the process goes andwhat happens to the metal.
In the course of work, the steel is heated. Depending on the material from which the sheet is made, it acquires a red or white tint. During the hardening process, the metal becomes stronger than it was before the procedure. Durability increases in the following cases:
- When the alloy heats up to a certain point. The process of destruction of the crystal structure begins.
- Metal transforms into a soft mass. Crystals become mobile. They become fine grained. After the product is cooled, the grains do not lose their structure. There is a strong bond between them. As a result, the steel becomes strong, but at the same time brittle.
Many are interested in how to harden a knife. Experts advise to work only with a cutting edge. In this case, the product will last a long time.
Method of testing metal for hardness
Many people use a stainless steel knife in everyday life. If they do not know if it needs heat treatment to increase wear resistance, look at the degree of hardness of the metal.
What is this? 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. The indenters used are solid balls and diamond cones with a 120° apex angle and a rounded sharp end.
Because of its simplicity, this method is oneof the most common material testing methods.
How to determine the degree of metal hardness without special tools?
At home, you can determine the degree of hardness of the product without a device. To do this, stock up on a 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, it will not cut the glass (maximum will leave a couple of scratches). When the metal is hard, it is difficult to take it with a needle file. After some effort, it may leave a noticeable mark on the glass.
If the metal was subjected to strong hardening, then it is almost impossible to take it with a needle file. The product easily cuts glass. In the process, you can hear a specific crunch.
What are the types of home hardening?
Before you harden stainless steel, you should find out what methods are available for working at home. Much depends on the right task. It is important to consider what grade of steel the stainless steel has. There are various modes of metal hardening:
- Hardening in a single environment. It is considered one of the simplest methods. It must be remembered that the method is not suitable for metal, which 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 percentagecarbon.
- Intermittent hardening 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 metal with high carbon content. It allows steel to be hardened without cracking. The method is considered difficult to perform at home. It should be used for products with a high carbon content.
- To harden a stainless steel step by step, you must first heat the metal, and then lower it into hot water with the addition of s alt. The product is kept in a s alt bath for up to 5 minutes. There is a gradual cooling. The product will not be affected by thermal stress. The advantage of this method is that it avoids cracks and other damage to the metal. The final step is to cool the sheet in the fresh air. This method is designed for thin metal, which contains a lot of carbon.
- 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, it can be seen that the products receive surface strength. The core of the metal remains ductile. The method is perfect for hardening parts that can withstand heavy loads.
- After release method. 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 increases.
What is used to cool stainless steel at home?
At home, for cooling after hardening the metal is used:
- Water. It quickly copes with the function of a metal cooler. It is not recommended to place metal with a high percentage of carbon in water. The product may be deformed. This medium is suitable for low carbon stainless steel.
- If a person wants to evenly cool the product after hardening, then he will need mineral oil. It allows the metal to cool slowly and does not cause deformation. This method is excellent for alloy steel.
- Sodium chloride or hydroxide presented in aqueous solution. The concentration of the substance should not exceed 10 percent. The metal product will be evenly cooled. The desired method is applied to steel with a high carbon content.
- Various polymer solutions. These include detergents. The method is good because it does not cause deformation of the material. There will be no defects on the product.
Table of metal cooling temperature after quenching
| Recommended environment for cooling hardened metal | Suitable temperature |
| Water | 20 to 80 degrees |
| Butter | 20 to 200 degrees |
| Saline solutions | 20 degrees and above to infinity |
What do you need to know to harden stainless steel at home?
Before carrying out this operation at home, you should learn some rules:
- If the metal has an increased hardness, then it needs to be heated as much as possible. It is best to wait until the product turns crimson.
- If a large amount of carbon is noted in the composition of the steel, then you need to be careful about the cooling process.
- If the product requires hardening over the entire surface, then it should be evenly heated on each side.
- Do not allow stainless steel to overheat. The surface must not show spots as a result of heating.
- Before starting work, you need to prepare special tongs. You will need a container to cool the metal.
Expert Tips
Experts advise hardening stainless steel over an open fire. The flame of a fire is best suited for these purposes. It is recommended to use ready-made coals. They keep the desired temperature for quite a long time.
If the product requires partial hardening, then a blowtorch should be used. It is suitable for working with cutting edge and other small parts. It is important not to overexpose the parts on fire.
Beginners often ask how to temper stainless steel according to the instructions. It is also important to know what safety precautions must be observed when working with it. If the cooling phase is done with oil, keep a distance from the container to avoid burns.
How to lower the hardness of stainless steel with tempering?
Vacation is used to eliminate increasedmetal hardness. The product is heated to the maximum temperature, and then gradually cooled in air.
For holidays, you can use temperatures not exceeding 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 up to 500 degrees. If a person works on parts designed for shock loads, then he can use a temperature regime from 500 to 700 degrees.
How to harden stainless steel? Safety instructions
To ensure that working with metal does not harm human he alth, the following safety precautions must be observed:
- You should regularly ventilate the room in which the metal hardening process takes place. It is recommended to install a special hood in the room. Children and animals should not be allowed into the room where work is taking place.
- In the process you need to use special gloves. As soon as the tools begin to glow, they are immersed in water until they are completely cool.
- When working with fire, you must comply with fire regulations, do not approach the fire with flammable liquids.
- If the product is hardened in oil, then the container is tightly closed with a lid.
- You need to work in special protective clothing. Sleeves and legs must be covered as there is a risk of burning limbs.
So, we looked at how to harden stainless steel. As you can see, this operation can be done with your own hands at home.conditions. The main thing is not to forget about safety precautions and follow the instructions exactly.
