440 steel - stainless steel. Steel 440: Characteristics

Steel is a compound of iron and carbon. The types of this material are determined not due to the ratio of the main components, but on the basis of impurities and additives that give the product different properties and characteristics.

Types of steel, according to pricing policy, can be divided into subgroups: cheap, popular and expensive. It all depends on the purpose of the material, the difficulties of its production. Moreover, there is no clearly bad or good alloy, since this material contains a whole range of characteristics that meet certain conditions. Specifically, this can be seen if we consider, for example, 440 steel.

Steel components

High-quality steel should be characterized at the same time by wear resistance, strength, elasticity, ductility, rigidity, anti-corrosion ability and endurance of sharpening. In practice, almost all of these properties contradict each other. One of the main elements of the alloy, responsible for hardness and stiffness, is carbon. Compounds with a high content thereof include those in which the concentration of a given chemical element is more than 0.5%. The property of wear resistance and low susceptibility to corrosion gives chromium steel. If its level is more than 13%, then this is a stainless product.

Granularity, strength, rigidity gives the alloy manganese. It is used at the forging and rolling stage. This is the so-called deoxidized steel.

To prevent products from this material from being brittle and brittle, and at the same time being resistant to heat, molybdenum is added to the compound. In this case, the alloy is called air hardened.

Helps reduce corrosion risks and gives nickel hardness. The strength property provides the material with silicon. Tungsten and vanadium give the alloy strength and wear resistance.

Features of steel 440

440 steel refers to stainless materials. It is used mainly for the manufacture of knives, building structures. A distinctive feature of this alloy is corrosion resistance and high strength. Also, the advantage of this series is its resistance to environmental factors, water, food, weak acids and alkalis.

Steel grade 440 includes subspecies 440A, 440V, 440C, and the 440A series is softer than others, and 440C is harder. However, the minus 440C is fragility and relatively low resistance to rust in relation to 440A and 440V. It turns out that with prolonged contact with moisture or aggressive environments, corrosion can occur. Although additional properties that prevent rust are given to this alloy due to its smooth polished surface.

It is not recommended to use 440 steel at a temperature higher than its heating during tempering, since in this case the mechanical properties of the alloy will be lost.

The chemical composition of 440 steel

Steel 440, the characteristics of which directly depend on the chemical composition, according to the series, contains the elements shown in the table below.

As can be seen from the table, the lowest carbon content in the 440A series, the highest - 440C, that is, the last brand is stronger than all, and the first is the most resistant to corrosion. Although all series of this brand are quite high quality and tolerate loads well.

Physical properties and heat treatment of 440 stainless steel

Steel 440 physical characteristics for series A, B and C has the following:

• material density - 7650 kg / cu. m;
• modulus of elasticity - 200 GPa;
• thermal conductivity - 242 W / m kb .;
• specific heat - 460 J / kg.kb .;
• electrical resistivity is 600.

The hardness of 440 steel varies between 56-58 units.

The average coefficient of thermal expansion, which is measured in mm / m / degrees Celsius, in the 440A series is 10.1; 440V - 10.3; 440C - 11.7.

The heat treatment of this material goes through the following stages:

• annealing;
• hardening;
• vacation.

Annealing takes place at a temperature of + 850-900 degrees Celsius, followed by a constant decrease to _600. Cooling occurs by air. Then - the procedure of fading annealing at 735-785 degrees and cooling in the furnace.

Hardening is carried out at + 1010-1065 degrees Celsius. Extinguishing - with warm oil or air.

Vacation takes place at a temperature of + 150-370 degrees, due to which the material is given the necessary hardness. Among the varieties of such a material as 440 steel, the mechanical characteristics are best for the 440C grade. This alloy is the most expensive and reliable. It sets the standard for product quality.

Scopes of steel 440

440 stainless steel is used in most cases for making knives. The rental of this alloy is intended for construction products that have welded or other joints.

Sheets of finished products are available in thicknesses from 4 to 50 mm. 440 steel does not require additional heating and heat treatment during welding with it. Convenient and reliable alloy for the production of bearings, parts of pipe fittings.

Large awkward knives are produced from 440A brand, including for underwater work and hunting. Blades from the 440C series have excellent cutting properties and good sharpening endurance, which is why this steel is used for the production of elite cutting tools.

You need to know when buying a knife marked "440" that a less expensive alloy is used here - 440A. If more expensive 440V and 440C connections are used, manufacturers always pay attention to this.

Alternative brands

There are a number of alternative grades that can replace this alloy. For example, the 440A / B series has additional properties that improve corrosion resistance. 440F steel has higher machinability with similar strength. The 420 grade is inferior in terms of hardness. The 416 series has increased machinability but lower reliability.

If you make knives from the brand 440A and its analogues, then such products are suitable for everyday use. Although, it is worth considering the quality of hardening. The company Sog has proven itself in this process. The Rendel company mainly produces knives from 440B steel.