Steel P6M5: characteristics, application

The alloy element of the eighth group of the Mendeleyev periodic system with atomic number 26 (iron) with carbon and some other elements is commonly called steel. It has high strength and hardness, lacks ductility and toughness due to carbon. The alloying elements increase the positive characteristics of the alloy. Nevertheless, steel is considered to be a metallic material that contains at least 45% iron.

Consider an alloy such as P6M5 steel, and find out what characteristics it has and in what areas it finds application.

Manganese as an alloying element

Until the 19th century, ordinary steel was used to process non-ferrous metals and wood. Her cutting characteristics for this was quite enough. However, when trying to process steel parts, the tool quickly heated up, worn out and even deformed.

The English metallurgist R. Müshett, by conducting experiments, found out that in order to make the alloy more durable, it is necessary to add an oxidizing agent to it, which will release excess oxygen from it. Steel cast steel was added to the mirror iron, which contained manganese. Since it is an alloying element, its percentage should not exceed 0.8%. Thus, P6M5 steel contains from 0.2% to 0.5% of manganese.

Tungsten Iron

Already in 1858, many scientists and metallurgists worked on obtaining alloys with tungsten. They knew for sure that this is one of the most refractory metals. Adding it to steel as an alloying element made it possible to obtain an alloy that could withstand high temperatures and not wear out at the same time.

Steel P6M5 contains 5.5-6.5% tungsten. Alloys with its content often begin with the letter "P" and are called high-speed. In 1858, the first steel containing 9% of tungsten, 2.5% of manganese and 1.85 of carbon was produced by Muyette. Later, adding an additional 0.3% C, 0.4% Cr and removing 1.62% Mn, 3.56% W, the metallurgist obtained an alloy called samocal (P6M5). In its characteristics, it is also similar to steel P18.

Deficiency of tungsten

Of course, in the 1860s, when many elements were in full abundance, steel with the addition of tungsten was considered the most solid. Over time, this element in nature is becoming less and the price of it is growing.

From an economic point of view, adding a large amount of W to steel became impractical. For this reason, P6M5 steel is much more popular than P18. Having looked at their chemical composition, it can be seen that the content of tungsten in P18 is 17-18.5%, while in the tungsten-molybdenum alloy it is up to a maximum of 6.5%. In addition, up to 0.25% copper and molybdenum up to 5.3% are present in the samokal.

Other alloying elements

In addition to the above-mentioned carbon, manganese, tungsten and molybdenum, P6M5 also contains cobalt (up to 0.5%), chromium (4.4%), copper (0.25%), vanadium (2.1%) , Phosphorus (0.03%), sulfur (0.025%), nickel (0.6%) silicon (0.5%). What are they for?

Each alloying element has its own function. For example, chromium is necessary for thermal hardening, and nickel increases the viscosity. Molybdenum and vanadium virtually eliminate embrittlement after tempering. Some of the alloying elements improve the properties of steel, such as red hardness and hot hardness.

The P6M5 steel, the characteristics of which we are studying, has a hardness of 66 HRC in the quenched state at a test temperature of up to 600 ° C. This means that even with strong heating, it does not lose its strength characteristics, and therefore does not wear out or deform.

The designation P6M5

The decoding of steel depends on how it is made, what alloying elements it includes and how much it contains carbon. There are different notations for different types. If, for example, the alloy does not contain alloying elements, it is denoted "St" and a number that indicates the average carbon content in the steel (St20, St45).

In low-alloy alloys, first comes the percentage of carbon, and then the letters denoting the chemical elements (10ХСНД, 20ХН4ФА). If there are no numbers near them, as in the example, then the content of each of them does not exceed 1%. The letter "P" in the alloy mark indicates that it is a high-speed (rapid).

Next is a number - this is the percentage of tungsten (P9, P18), and then, letters and numbers are the alloying elements and their percentage. It follows that high-speed steel P6M5 contains up to 6% tungsten and up to 5% molybdenum.

Annealing

As a rule, the production of such an alloy is classical and is used for all high-speed steels. However, it should be borne in mind that in order for the tungsten-molybdenum alloy to be really strong, hard and wear-resistant, it must be annealed.

If other brands, for example, St45, lose their strength properties during annealing, then high-speed ones, on the contrary, improve and become stronger and harder. This is why P6M5 is annealed before quenching. How does this happen?

Rolling (for example, a sheet of "steel P6M5") with a thickness of about 22 mm in a special furnace is heated to a temperature of 870 ° C, then it is cooled to 800 ° C, and then heated again. Such cycles can be about 10.

In addition, after the fifth, it is necessary to gradually reduce the temperature. For example, the heating again, but to 850 ° C, cool to 780 ° C. And so on until it reaches 600 ° C.

Such a complicated annealing process is explained by the presence of austenite grains in alloyed alloys, which is extremely undesirable. Heating and cooling allows maximum dissolution of alloying elements, but at the same time austenite will not grow.

If the temperature regime can not be maintained and annealed at a temperature of more than 900 ° C, an increased amount of austenite is formed in the alloy and the hardness is lowered. Cooling is recommended to be carried out with the help of oil baths, this will protect the tungsten-molybdenum alloy from cracks and nadals.

Method of manufacturing Р6М5

Of course, like any other alloy, P6M5 is manufactured in a different range. So, in some shops high-speed hot steel is poured into ingots. In another production, it is rolled hot rolled. To do this, heated ingots are crimped between the rolls of the rolling mill. Its shape will depend on the shape of the shafts themselves.

The steel grade P6M5 is widely used for parts operating at high temperatures. For this reason, recently a very popular way of making steel is powder.

When pouring hot steel into ingots, a very rapid release of carbides from the melt occurs. In some areas, they form uneven areas of the cluster, which in the future are the site of nucleation of cracks.

Powder manufacture uses a special powder, which contains all the necessary components. It is sintered in a special vacuum container with high temperature and pressure. This helps to make the material homogeneous.

Application

Steel P6M5 is widely used in various industries. Most often it is used for the manufacture of cutting tools for turning, milling and drilling machines in metallurgy. This is due to its characteristics of strength, heat resistance, hardness.

As a rule, drills, taps, dies, cutters are made from it. Metal cutting tool from steel P6M5 is excellent for cutting at high speeds, in addition, it does not require cooling with soot. The knife from steel Р6М5 is also not a rarity.

Since the tungsten-molybdenum alloy has a high hardness and high viscosity, it is often used to make knives with strong handles and beautiful patterns.

Alloying elements in the necessary quantity allowed to create a unique steel, which practically does not rust and has good grinding. This makes it possible to increase the cutting speed by 4 times in plumbing work.

It is also used for the production of heat-resistant ball bearings operating at high speed at a temperature of 500-600 ° C. Analogues of the P6M5 alloy are P12, P10K5F5, P14F4, P9K10, P6M3, P9F5, P9K5, P18F2, 6M5K5. If tungsten-molybdenum alloys, as a rule, are used to make tools for roughing (drills, cutters), then vanadium (P14F4) for finishing (scanning, broaching). On each cutting tool there is necessarily a marking, which allows you to find out what alloy it is made of.