What is the hardness of steel 40x. Explanation of abbreviations

With strong heating, almost all materials change their physical characteristics. In some cases, heating is carried out purposefully, since in this way it is possible to improve certain performance qualities, for example, hardness. Heat treatment has been used for many years to increase the surface hardness of steel. Hardening should be carried out taking into account the characteristics of the metal, since the technology for increasing the surface hardness is created based on the composition of the material. In some cases, hardening can be done at home, but it should be borne in mind that steel is a difficult-to-machine material and, in order to impart plasticity, it is necessary to carry out strong heating to high temperatures using certain equipment. In this case, we consider the features of heating 40X steel to increase ductility and conduct quenching or tempering.

Steel 40X

As previously noted, for the correct quenching and tempering of steel, its composition and many other features should be taken into account. You can choose the right heat treatment modes based on the following information:

1. The considered steel belongs to the structural alloyed group. The doped group is characterized by the content a large number impurities that determine the change in performance, including hardness.
2. Used in industry to create shafts, axles, rods, mandrels, racks, bolts, bushings, gears and other parts.
3. Hardness index before heat treatment HB 10 -1 = 217 MPa.
4. The temperature of the critical points determines the moment at which 40X steel begins to lose its qualities due to heat treatment: c 1 \u003d 743, Ac 3 (Ac m) \u003d 815, Ar 3 (Arc m) \u003d 730, Ar 1 \u003d 693.
5. At a tempering temperature of 200 °C HB = 552.

The decoding of steel 40X indicates that the material contains 0.40% carbon and 1.5% chromium.

Download GOST 4543-71 "Rolled products from alloyed structural steel 40X"

hardening process

The process of high temperature treatment of 40X steel and other alloy is called hardening. It should be noted that heating is carried out up to certain temperature, which was determined through numerous tests. The holding time after which cooling is carried out, as well as other points, can be found in special tables. It is rather difficult to carry out heating at home, since in this case it is necessary to reach a temperature of about 800 degrees Celsius.

The result of strong heating and exposure of the metal 40X for a certain time, followed by a sharp cooling in water, is an increase in hardness and a decrease in ductility. In this case, the result depends on the following indicators:

1. metal heating rate 40X;
2. exposure time;
3. on the cooling rate.

When working at home, consider the processing temperature and cooling time.

When choosing a surface heating method, attention should be paid to HDTV. This method is more popular than conventional volumetric processing due to the fact that the required temperature is reached in a shorter time.

In the production of steel, the final product is obtained when all the oxide that it takes out of its natural state is eliminated, being the most important material for construction. Low alloy steel: Steel to which other metals are added to improve its properties. High mechanical strength. Steels are materials with high mechanical strength when subjected to tensile and compressive stresses and are supported by the chemical contribution of the steels. With the help of laboratory tests, the tensile and compressive strength are determined by evaluating its elastic limit and breaking strength.

At home, HDTV is used extremely rarely. After carrying out work with the use of HDTV, the operational strength of the part increases, which is associated with the appearance of surface compressive stresses.

Hardening 40X using the example of an M24 bolt product can be done as follows:

1. the electric furnace is heated;
2. warming up to 860 ° C should be carried out, for which in some cases it takes 40 minutes;
3. the time required for austenitization, after which cooling is carried out, is 10-15 minutes. Uniform yellow products - a sign of the correct passage of the 40X hardening process;
4. the final stage is cooling in a bath of water or other liquid.

It is impossible to determine on your own the moment after which the metal should be cooled in industrial and domestic conditions. That is why, according to the studies, it was assumed that it takes 1.5-2 minutes per millimeter to heat the metal in electric furnaces, after which the structure can be overheated.

Elasticity: The elasticity of steels is very high, when tensile tested, the steel returns to its original state in tension until the elastic limit is reached. Weldability: This is a material that can be joined by welding, and thanks to this, a number of designs with straight parts can be made.

Ductility: Steels have a high ability to work with them, bend them and bend them. Reliability: means that heat and impact can give any desired shape. Workability: They can be cut and drilled even though they are very stable and still retain their effectiveness.

The determination of hardness is carried out according to the Rockwell method. The improvement made by tempering or quenching can be measured using the HRC designation. Standard designation HR, to which a letter is added according to the type of test performed. The designation HRC is the most common, the last letter means the use of a diamond cone with an angle of 120 0 when testing.

Oxidation: Steels have a high oxidizing ability when exposed to air and water at the same time and the material corrodes if it is salty water. Heat and Electricity Transmitter: Steel is a high accuracy transmitter and at the same time is very weak at high temperatures, so it is preferable to use steels for nickel or aluminum or try to protect them by making them ventilated and avoid making fuel or plastic factories with this type of material.

These two disadvantages are manageable considering the use of materials and Maintenance which is provided to them. Quality control of steel in our country is based on two tests: Chemical test: This is done because there are many types of steel and the company that produces them is required to prove its chemical composition.

Vacation and normalization

Tempering is carried out immediately after hardening is completed, since there is a high probability of cracks in the structure. In this case, the product is heated to a point below the critical one, holding is carried out for a certain period of time and cooling is performed. Tempering provides an improvement in the structure, eliminates stress and increases ductility, and eliminates the brittleness of 40X steel.

Axial Tensile Test: This test is always performed randomly on the obtained steels. The purpose of this test is to obtain in any steel its elastic limit and tensile strength, in order to know the quality of the material and compare it with the parameters that are set for steels. good quality, the percentage of elongation is also obtained, which allows you to find out the ductility of the steel.

• Werner or caliber.
• Measuring tape.

After the sample is prepared, press on the ends with a press to continue applying the load. Before starting the pulling process, in order to be able to then measure how much elongation was before failure, so that the percentage of doubling was centimeter and centimeter of the entire panel. Measuring results: Elastic zone: this is the zone in which, when the beam is unloaded, it returns to its original shape.

There are three types of heat treatment under consideration:

1. Low tempering determines the heating of the surface up to 250 °C with exposure and cooling in air. It is used to relieve stress and slightly increase ductility with virtually no loss of hardness. In the case of a structural alloy, it is used extremely rarely.
2. Medium tempering allows you to heat the product up to 500 °C. In this case, the viscosity increases significantly, and the hardness decreases. Use this method of heat treatment when receiving springs, springs and some tools.
3. High allows you to heat the part up to 600 ° C. In this case, martensite decomposes with the formation of sorbite. Such a structure is presented the best combination strength and plasticity. It also increases the impact strength. Use this method of heat treatment to obtain parts used under shock loads.

Plastic zone: refers to the area where when the beam is deformed and the loading is stopped, it does not return to its original position.

• Maximum carbon 0.3% Maximum sulfur 0.05% Maximum phosphorus 0.04%.
• The elastic limit cannot exceed 30% of its minimum value.

Structural profiles cannot show visible damage, the first thing they must have is a good appearance.

If it's Venezuelan steels, you can omit that because they already come with those considerations. Axial tensile test: Determine its physical and mechanical characteristics, which are also normalized. Structural profiles must be controlled.

Another type of common heat treatment is normalization. Often, normalization is carried out by heating the metal to the upper critical point, followed by exposure and cooling in a normal environment, for example, at outdoors. Normalization is carried out to give a fine-grained structure, which leads to an increase in ductility and toughness.

Oxidation: This occurs when steels are in direct contact with water and air at the same time. Corrosion: It is closely related to oxidation with the difference that occurs when the material is exposed to saline. Conductivity: Steel is a highly accurate transmitter and at the same time very weak at high temperatures, so it is preferable to use steels for nickel or aluminum or try to protect them by venting and avoid making fuel or plastic factories with this type of material.

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All detailed characteristics of these mechanisms are given in our catalog.

The chemical composition of steel.

The main indicators of the chemical composition of Steel 40X are specified in its marking - from 0.36 to 0.44%, and the letter X means the presence of an alloying element - chromium, the proportion of which in the composition is from 0.8 to 1.1%. Below is the full line-up:

• iron (Fe) - up to 97%;
• silicon (Si) - from 0.17 to 0.37%;
• manganese (Mn) - from 0.5 to 0.8%;
• nickel (Ni) - up to 0.3%;
• sulfur (S) - up to 0.035%;
• phosphorus (P) - up to 0.035%;
• chromium (Cr) - from 0.8 to 1.1%;
• copper (Cu) - up to 0.3%;

Existing GOSTs for Steel 40X.

Due to the wide variety of existing rolled products and blanks from Steel 40X, the quality and characteristics of the entire range of products are regulated by the following GOSTs:

• circle Sal 40X GOST 2590-2006 (GOST 2590-88) circle (bar) steel hot-rolled;
• circle Steel 40X GOST 7417-75 circle (bar) calibrated;
• circle Steel 40X GOST 14955-77 circle (rod) with a special surface finish (silver);
• hexagon Steel 40X GOST 2879-2006 (GOST 2879-88) hot-rolled hexagon;
• hexagon Steel 40X GOST 8560-78 calibrated hexagon;
• sheet Steel 40X GOST 19903-74 hot-rolled sheet;

Steel 40X. Mechanical properties.

Mechanical properties depending on the section

Mechanical properties of Steel 40X depending on tempering temperature

Mechanical properties at elevated temperatures

endurance limit

Impact strength Steel 40X KCU (J / cm.sq.)

Hardenability of steel according to GOST 4543-71

Physical properties of Steel 40X

Explanation of abbreviations

Samples of products from steel 40X.

Below are samples of some products manufactured by our organization from 40X steel.