Steel 5xnm machinability

Tool die steel 5ХНМ

Brand 5ХНМ – purpose

Tool die steel 5ХНМ is used for hot deformation of non-ferrous light alloys - high-speed machine stamping dies; for the production of press dies, hammer dies of pneumatic/steam-air hammers (the weight of the falling components is more than 3 tons), matrix blocks - inserts of horizontal forging machines.

Steel 5ХНМ - domestic analogues

Material 5ХНМ - characteristics

5ХНМ

Home/Characteristics of Steel and Rolled Metal Grades/5ХНМ

Characteristics of the material. Steel 5ХНМ.

Chemical composition in % of material 5 ХНМ in accordance with GOST 5950-2000

Temperature of critical points steel grade 5 XHM (5 ХНМ )

Technological properties of grade 5 XNM

Mechanical properties of steel 5 ХНМ depending on the section

Steel hardness 5 ХНМ (HRC e , НВ )

The purpose of final heat treatment is to obtain in the finished tool an optimal combination of basic properties: hardness, strength, wear resistance, toughness and heat resistance.

The most common final heat treatment process for hot forming tools consists of quenching and tempering. The wide variety of operating conditions for such a tool predetermines not only the use of different steels, but also the need to obtain in each specific case the optimal combination of properties for the given conditions through the correct choice of heat treatment modes. At the same time, depending on the purpose of the tool, it is possible to select different heating temperatures for quenching, quenching media and cooling methods, and tempering temperatures. The quenching and tempering modes are not universal, but they should be assigned differentially in accordance with the operating conditions of the tool.

In particular, it should be taken into account that with increasing heating temperature for quenching, the heat resistance and hardenability of die steels increases, but due to grain coarsening, their toughness decreases. Therefore, for example, for a pressing tool operating with high heating, but without significant dynamic loads, it is advisable to increase the heating temperature for hardening to obtain greater heat resistance.

At the same time, when choosing quenching and tempering modes, one should take into account their influence on the deformation of the tool during heat treatment and the possibility of subsequent machining.

Increasing the tempering temperature generally increases the toughness of the steel, but reduces its hardness, strength and wear resistance. In this regard, to preserve the wear resistance and hardness of the steel, the tempering temperature is chosen to be lower, but not lower than the heating temperature of the tool during operation.

Physical properties of the 5ХНМ brand

Heat resistance, red resistance of 5XHM steel

Designations:

Legend

Mechanical properties

Weldability

Characteristics of alloyed alloy 5ХНМ

Among the most noticeable properties of 5KhNM steel are high strength and high toughness, excellent wear resistance and heat resistance, scale resistance and good thermal conductivity. However, this alloy is not suitable for welding.

What do alloying elements give to this alloy? The use of chromium makes the metal more elastic, hard and durable. This element also increases the hardenability of steel and, in general, significantly improves many of the physical properties of the metal. Nickel is also used to increase strength, but here its role is to lower the cold brittleness threshold of the alloy. A side effect of this is a tendency to temper brittleness, but the problem is completely solved by the use of molybdenum. Combining with chromium and nickel, this chemical element significantly increases the toughness and strength of the metal, however, reducing its thermal conductivity.

Tool die alloy steel 5ХНМ can boast the following physical and mechanical properties:

Weldability and substitutes for structural and tool steels

A table is provided of the main grades of structural and tool steels, including stainless and heat-resistant, and recommendations for welding parts made from them.
STEEL GRADES

If, in any case, you need to weld steel for slightly different purposes, you can use the following recommendations.
WELDABILITY OF STEEL
The main characteristics of the weldability of steels are their tendency to crack and the mechanical properties of the weld.

According to weldability, steel is divided into four groups: 1 - good weldability; 2 - satisfactory weldability; 3 - limited weldability; 4 - poor weldability

To group 1

include steels, welding of which can be performed without heating before welding and during the welding process and without subsequent heat treatment. But the use of heat treatment is not excluded to relieve internal stress. Steels St1 - St4 according to GOST 380-94 have good weldability; steel 08; 10:15; 20; 25 according to GOST 1050-2013; steel 15L; 20L according to GOST 977-88, steel 15G; 20G; 15X; 20X; 20ХГСА; 12ХН2 according to GOST 4543-71. Steel 12Х18Н9Т; 08Х18Н10; 20Х23Н18 according to GOST 5632-72

To group 2

mainly include steels, when welded under normal production conditions, cracks do not form, as well as steels that require preheating to prevent cracks, steels that must be subjected to preliminary and subsequent heat treatment. St5ps steels have satisfactory weldability. St5sp according to GOST 380-94. steel 30; 35 according to GOST 1050-2013; steel Z0L; 35L according to GOST 977-88; steel 20ХНЗА; 12Х2Н4А according to GOST 4543-71.

To group 3

include steels prone to cracking under normal welding conditions. They are pre-heated and heated. Most steels in this group are also heat treated after welding. St6ps steels have limited weldability. St6sp according to GOST 380-94; steel 40; 45; 50 according to GOST 1050-2013; steel 30ХМ; 30ХГС; ZZHS; 20Х2Н4А according to GOST 4543-71; steel 17Х18Н9; 12Х18Н9 according to GOST 5632-72.

To group 4

include steels that are most difficult to weld and prone to cracking. They must be welded with preliminary heat treatment, heating during the welding process and subsequent heat treatment. 40G steels have poor weldability; 45G; 50G; 50Х according to GOST 4543-71. steel 55L according to GOST 977-88; U7 steel; U8; U8A; U8G; U9; U10; U11; U12 according to GOST 1435-90; steel 65; 75; 85; 60G; 65G; 70G; 50ХГ; 50HGA; 55С2; 55С2А; 60С2; 60С2А according to GOST 14959-79; steel X12; XI2M; 7X3; 8X3. CHVG; ХВ4; 5ХГМ; 6ХВГ according to GOST 5950-73.

Hammer dies

Dies made of steels 5ХНСВ, 5ХНМ, 5ХНВ and 5ХГМ.
To eliminate internal stresses arising during forging, to refine the grain, obtain a uniform structure and reduce the hardness, die blanks (cubes) are subjected to annealing or normalization with a high tempering according to the regime for a given steel. The quality of dies and their durability in operation are affected by heat treatment - hardening and tempering of dies. If the heat treatment of the dies is carried out unsatisfactorily, then cracks may appear in the dies (during the heat treatment or after some time of operation). The dies are destroyed due to significant internal stresses arising during heating and cooling. Particularly high stresses during heat treatment of large dies. When heated, internal stresses arise due to temperature differences in individual zones of the die. To reduce internal stresses, heating for quenching and tempering should be carried out in such a way that there is a minimum difference between the surface temperature and the temperature of the die core.

To prevent the formation of significant internal stresses from uneven heating, the dies must be slowly heated to 500-600 ° C. With a further increase in temperature, heating can be faster. Usually, when heating for hardening, the dies are loaded into a furnace having a temperature of no higher than 650 ° C. When loading cold dies, the furnace temperature decreases, and the larger the dies, the more so.

To protect against oxidation and decarburization when heated, the working surface of the die is covered with spent carburizer, coated with fireclay clay on top and placed in the oven with the figure up (Fig. 183, a) or with the figure down in the iron

a box into which a layer of spent carburizer is poured (Fig. 183, b).

The hardening temperature of dies is 820-880° C (lower temperature for hardening small dies, higher temperature for large ones). The hardening temperature is 840–860° C for steel 5KhNSV and 820–860° C for steels 5KhNM, 5KhNV, 5KhGM.

For dies with the smallest side (height) of 250-700 mm (when heated in an electric furnace), the holding time after loading into the furnace is 40 minutes - 2.5 hours; heating to the hardening temperature for 11-23 hours, holding at the hardening temperature for 2-5.5 hours. After holding at the hardening temperature, the dies are cooled in air to 750-780 ° C for 15-40 minutes to reduce stress and deformation and cooled in oil with a temperature not exceeding 70° C or in air. A more uniform structure is obtained by cooling in oil. The stamp is immersed in oil with the working part down. During cooling, the stamp is always in a suspended state. The stamp is kept in oil until the temperature of the heated surface of the stamp drops to 200-150° C. Depending on the size (250-700 mm), the stamps are kept in oil from 30 minutes to 2 hours.

After hardening, the dies are immediately tempered. Tempering the dies reduces their hardness and reduces the internal stresses that arise in the dies as a result of hardening. Quenching stresses in dies can be so great that if the die is left without tempering after quenching, then after some time cracks will form in it. If a hardened stamp is placed in a furnace heated to the tempering temperature (500-600 ° C), then with rapid heating of the surface layers and a significant difference between the surface temperature and the core temperature, cracks may occur in the stamp. Therefore, after hardening, the dies are placed in a tempering furnace heated to a temperature not exceeding 400 ° C, and then heated to a given tempering temperature. Tempering temperature and hardness after tempering depend on the steel and die size. Higher hardness (HRC 40-44) is allowed for small dies in which the deformed metal heats up faster. These dies are slightly deformed during hardening, so hardening and tempering can be carried out after final processing on metal-cutting machines. Medium dies should have a hardness of HRC 36-41. This hardness allows the use of a combined manufacturing method in the following sequence: rough cutting of a figure with a tolerance, heat treatment, final cutting after heat treatment.

Large dies must have high viscosity; they are tempered to a hardness of HRC 35-38. First, the cubes are hardened and released, and then the shape is cut. Worn dies are processed by cutting without intermediate annealing, then heat treatment is carried out again. Tempering temperatures and hardness of hammer dies are given in table. 25.

Dies with the smallest side (height) of 250–700 mm are heated in an electric furnace to tempering temperature for 9–25 hours and kept at tempering temperature for 1.5–5 hours. Since the tail part of the stamp must have increased viscosity, after general tempering temper the shank. To do this, the stamp is installed with the shank down on a special slot furnace or on a stove-stove. Heating is carried out until a blue or gray tarnish appears on the working part of the die, which corresponds to a temperature of 250-350 ° C. Tempering temperatures and the hardness of the shanks are given in table. 26.

To shorten the heat treatment cycle, the following method of hardening dies is recommended. The stamp heated to the hardening temperature is covered from the tail part with a hermetic box (Fig. 184) and in this form is immersed in oil. When cooling, the oil does not penetrate inside the box, since this is prevented by the air and oil vapor in the box. With this cooling method, the shank is not hardened, but is subjected to normalization with self-tempering to obtain the required

hardness, and therefore additional tempering is not required. A progressive method that shortens the heat treatment cycle and improves the quality of dies is the method of local hardening. The dies are heated in a special slotted gas oven when installed face down. With this method, the working part of the stamp is heated to the hardening temperature; heating of the shank does not exceed 450° C, i.e. there is a sharp decrease in temperature from the working to the tail part of the die; the shank remains soft. The dies are heated in a slot furnace without protective coating. The resulting thin layer of scale (a few hundredths of a millimeter) is easily removed from the stamp figure. After hardening, tempering is carried out according to the usual conditions for the working part.