When choosing a material for the manufacture of a metal product, several characteristics must be taken into account, including its stiffness modulus. This structurally insensitive indicator depends only on the nature of the material from which the power elements are made - stringers, frames, flat plates, etc.
The highest modulus of rigidity is steel, which, in turn, in its chemical composition is of two types. Firstly, it is alloy steel, in which alloying elements are specially added to obtain any necessary properties.
The main elements that affect the property of steel are carbon, silicon and manganese. Carbon with an increase in its content makes steel stronger and harder, while reducing its ductility. Silicon is introduced as a deoxidizer, however, when its content is more than one percent, the weldability of steel is much worse : the weld is made brittle. And such an element as manganese increases the cold brittleness and toughness of steel, also being a good deoxidizer.
As a rule, in addition to iron and carbon, any one component is added, so alloy steel is classified as three-component, four-component, etc. Sometimes it differs by the name of the alloying element, for example, chromium, chromium-nickel, chromium-nickel-molybdenum, etc.
Alloy steel contains more than one percent chromium or nickel. If it contains more than 0.5% vanadium, titanium, molybdenum, niobium, nitrogen, copper, etc., then it is considered to be doped with these elements.
Depending on the amount of added components, alloy steel is divided into the following subclasses:
- high alloy steel, in which the total content of alloying elements is at least ten percent;
- medium-alloyed - not more than eight percent;
- low alloy steel, in which only one element is added with an upper limit of no more than two percent.
Usually alloying elements significantly increase the cost of steel, especially since some of the added elements by themselves are scarce and expensive metals. On the basis of this, their addition to steel must be justified.
Alloy steel is marked as follows: the first two digits indicate the carbon content (hundredths of a percent), the letters symbolically indicate the added alloying element, the number after them indicates the percentage of this element. The letter “A” at the end of the marking means that this steel is of high quality with a low content of phosphorus and sulfur.
Another type of steel in chemical composition is carbon. Because of its simplicity of production and low cost, it is more often used in many industries.
One of the purposes of steel is its use in the manufacture of measuring and cutting tools, machine parts, dies with cold and hot deformation.
Tool steel can be alloyed and carbon, and depending on the standards regulated by GOST, for each specific metal product, it is necessary to use steel having a certain chemical composition.
For example, for surgical instruments, drills, chisels, hammers, screwdrivers, saws, milling cutters, etc., steel of a certain category is used - high-alloy, high-speed. It has high hardness, heat resistance and wear resistance. These unique properties are obtained by special alloying with the addition of tungsten carbide, as well as complex heat treatment.
For hammer, cold and hot dies, molds, etc., steel of such grades as X6VF, 9X, 5XHM, etc. is used.