Toughness - the ability of different materials to absorb the energy shock, which is one of the most important indicators of strength.Toughness of a material is usually defined by impact bending rectangular sample material, the estimated work to rupture or fracture of the sample at a certain impact load, which is an indicator of toughness.Defining it is held in a special device - pendulum.The sample with the middle notch test by hitting it with a knife pendulum.The test indicator of the metal may be conducted at a temperature from -100 ° C to 1200 ° C, depending on the metal and the purpose of the test.Toughness is a measure of the reliability of metal or other material that indicates its ability to resist fracture caused by the tensile stress between the atoms.
value toughness of steel is determined by the magnitude of the work, which is sufficient to break the sample of the steel.It denotes the set of letters and numbers.The first two letters - a symbol of toughness (COP).The third letter indicates the type of hub.Then there are the numbers.The first one shows the maximum energy from the impact of a pendulum, the second indicates the depth of the hub, and the third - the width of the test specimen.If the sample is tested at reduced or elevated temperature, then further specified numerical index, meaning that the temperature level at which the test was carried out.
Falling impact strength of metals at high temperature reduction is an indication of their brittleness.Brittleness - a increase in brittleness of metals at low temperatures.The phenomenon of cold cracking, and low-alloy steels exposed to some other metals - tantalum, tungsten, chromium, molybdenum, which consists of cubic lattice obemotsentrirovannoy metal atoms.Toughness metals depends primarily on the temperature.
toughness of the steel depends on the structure of the test steel, including its grain size and is a good indicator of the quality of the metal.Therefore, test the toughness widespread.The temperature range in which the toughness of steel decreases sharply, called the domain of thermal brittleness.And it is necessary that this area temperature brittleness temperature did not coincide with the work began.In other words, the operating temperature of metal should be higher than the threshold beyond which the embrittlement temperature region begins.This is to ensure that the material items began to crack and eventually not been destroyed.Criterion embrittlement temperature region is closely related with the level of the toughness of metals.
optimum toughness steels have heat-treated steel and quiet open-hearth steel, thermal performance field fragility which allow them to possess such characteristics.For each kind of steel GOST establishes a temperature at which the toughness is determined as well as the temperature which is optimum for use with one or another type of steel.Toughness of the steel depends not only on the temperature but also from various impurities, the presence of alloying elements and from the steel composition.Formation of products in steel hardening structures seriously reduces the toughness of the steel.For example, when welding with a specific violation of the technology works martensite formed, the toughness of the weld metal zone can be reduced by 13 times.
