How is the impact strength of metals determined?

Impact strength is the ability of various materials to absorb the energy of the shock load, which is one of the most important indicators of strength. The impact strength of a material is most often determined by the impact bending of a rectangular sample of the material, while the work is evaluated before breaking or breaking a particular sample under shock loading, which is an index of impact strength. Definition of it is carried out on a special device - pendulum copra. A sample of the material with a notch in the middle is tested by striking it with a pendulum knife. The test of this metal index can be carried out at a temperature of -100 ° C to 1200 ° C, depending on the metal and the purpose of the test. The impact strength of metals is an indicator of the reliability of a material, indicating its ability to resist the damage caused by the tensile stress between atoms.

The value of the toughness of steel is determined by the amount of work that is sufficient to destroy a sample of this steel. It is denoted by a combination of letters and numbers. The first two letters are a symbol of impact strength (COP). The third letter shows the type of concentrator. Then there are the numbers. The first shows the maximum energy from the pendulum impact, the second indicates the depth of the concentrator, and the third indicates the width of the test piece. If the sample was tested at a reduced or elevated temperature, then a digital index indicating the temperature at which the test was carried out is additionally indicated.

The drop in the toughness of metals with a large decrease in temperature is an indicator of their cold-brittleness. Cold-brittle is the increase in the level of brittleness of metals with a drop in temperature. Low- alloy steels and some other metals such as tantalum, tungsten, chromium, and molybdenum, which consist of a body-centered cubic lattice of metal atoms, are subject to such a phenomenon as cold brittleness. The impact strength of metals depends primarily on temperature.

The impact strength of steel is determined by the structure of the steel under test, including the size of its grains and is a good indicator of the quality of the metal. Therefore, the impact test is widely used. The temperature range in which the toughness of steel falls sharply is called the temperature brittleness region. And it is necessary that this region of temperature brittleness does not coincide with the temperature of the steel. In other words, the working temperature of metal products should be higher than the threshold beyond which the temperature brittleness region begins. This is to ensure that the material of the part does not begin to crack and in the end is not destroyed. The criterion of the region of temperature brittleness is closely related to the level of impact strength of metals.

The optimum toughness of the steel is heat-treated steel and quiet open-hearth steel, the parameters of the temperature-brittleness range of which allow them to have such characteristics. For each type of steel, GOST sets its temperature at which the toughness is determined, as well as the temperature that is optimal for working with a particular type of steel. Impact strength of steel depends not only on temperature, but also on various impurities, the presence of alloying elements and on the composition of the steel itself. The formation of quenching structures in steel products seriously reduces the toughness of the steel. For example, if martensite is formed during welding with a certain violation of the working technique, the impact strength of the metal in the welding zone can be reduced by a factor of 13.