An alloy of an element of the eighth group of the periodic system of Mendeleev with atomic number 26 (iron) with carbon and some other elements is usually called steel. It has high strength and hardness, and lacks plasticity and toughness due to carbon. Alloying elements increase the positive characteristics of the alloy. However, steel is considered to be a metallic material that contains at least 45% iron.
Let's look at an alloy such as R6M5 steel and find out what characteristics it has and in what areas it is used.
Main characteristics
The basic parameters of steel of this grade are: high toughness, excellent wear resistance, and a good level of grindability. This grade is used in the production of many types of blades and cutting equipment for working with structural strength steels.
Knife with a blade made of steel R6M5.
A tungsten-molybdenum alloy is the second name of this brand, which can retain its characteristic qualities even under extreme temperature changes. Moreover, its bending strength reaches 4700 MPa. Its combination with impact strength gives it a noticeable superiority over many of its peers.
Minuses
The main disadvantage is that due to the low chromium content, the alloy is susceptible to corrosion. The higher the temperature, the faster the destructive processes occur.
Other cons:
- A thin sharp cutting edge, even with slight pressure, leads to damage to soft tissues - a high probability of causing injury, not suitable for tropical fruits with soft skin, hard bone (mango, avocado - risk of bone chips getting into the pulp).
- The quality of sharpening decreases with frequent simultaneous cooling - the sudden release of tungsten energy affects the atoms of other elements of the crystal lattice.
- Loss of sharpening quality when not in use for a long period of time.
- Loss of properties due to prolonged exposure to negative temperatures in an environment with high humidity. reduction of service life due to icing and defrosting. If this happens, gradually defrost it in an oily, non-acidic solution. carefully remove plaque. During the first operation, after getting rid of ice, heat it up gradually.
- Difficulty of manual processing - without turning equipment it is difficult to sharpen the blade yourself.
- When sharpening by hand, it is not recommended to cut shortcrust pastry - one edge crumbles, the other shrinks.
- Contrary to its intended purpose, rapid manual cutting without proper training may result in injury. This also applies to work not at a right angle.
- Such knives will not be able to separate products of different densities (fish fillets from bones).
Application of R6M5 in production and everyday life
P6M5 is often used for the production of knives, both in mass production and in everyday life. It should be noted that a properly sharpened knife can handle almost any material; on the Internet you can find a video where you can see how a knife made from this brand cuts a metal plate.
Despite the high price, knives made from P6M5 are very popular in everyday life, but the problem is that a product made from this steel is difficult to sharpen and therefore most often such a knife can be found among hunters, tourists, etc.
In almost every home you can find power tools, but all technological equipment and tools are made from P6M5.
Drills made from this steel are used for various jobs around the house. This alloy is used to produce products such as:
- simple drills, sharpened on one side;
- made in the form of a crown, they are intended for drywall;
- with a spear-shaped ending.
Of course, drills for working with metal are also made from this steel.
In industry, R6M5 is used for the manufacture of various tools, for example:
sweeps;
dies (dishes);
slotting cutters;
blades for hand and mechanical hacksaws.
Sharpening features
Products made from R6M5 are subject to periodic dulling. We can immediately say that ordinary wheels made of electrocorundum are unlikely to help with sharpening. For this purpose, it is advisable to use abrasives made on the basis of CBN.
For sharpening and straightening, flat profile (PP) wheels, as well as cup wheels, are used. But sharpening with CBN-based wheels has its drawbacks, which are expressed in poor-quality surface cleanliness and the appearance of changes in the structure of the metal.
To achieve the maximum effect from sharpening the P6M5, it is recommended to sharpen in two passes:
- preliminary, for this purpose wheels with grain 40 are used;
- finishing, for this purpose use wheels with grain 25 - 16.
Carbon steels
Carbon tool steels are marked with the letter Y, and the number following it shows the carbon content in tenths of a percent. For the manufacture of tools, high-quality carbon steels of grades U7-U13 and high-quality steels of grades U7A-U13A are used. High-quality steels contain no more than 0.02% sulfur and phosphorus, high-quality steels - no more than 0.03%. According to their intended purpose, carbon steels are distinguished for use under shock loads and for statically loaded tools. Steel grades U7-U9 are used for the manufacture of tools when working with shock loads, which require high cutting ability (chisels, metal stamps, woodworking tools, in particular saws, axes, etc.). Steel grades U10-U13 are used for the manufacture of cutting tools that do not experience shocks or shocks during operation and have high hardness (files, scrapers, sharp surgical instruments, etc.). Simple cold-forming dies are sometimes also made from steel of these grades. Carbon hypoeutectoid steels, after hot plastic processing (forging or rolling) and subsequent cooling in air, have a structure consisting of lamellar pearlite and a small amount of ferrite, and hypereutectoid steels have lamellar pearlite and excess cementite, which usually forms a continuous or discontinuous network along the boundaries of the former grains austenite. Heat treatment of carbon tool steels consists of two operations: preliminary and final treatments. Preliminary heat treatment of steels consists of annealing at 740-760 °C, the purpose of which is to obtain a microstructure consisting of granular pearlite - pseudo-perlite, since with such a microstructure after subsequent hardening the most uniform properties are obtained. In addition, this structure facilitates the machining of the tool. The final heat treatment consists of hardening and low tempering. Quenching is carried out in water from 780-810 °C, that is, at temperatures for hypoeutectoid steels lying slightly above LS3, and for hypereutectoid steels lying below Ast.
Carbon steels have a very high critical hardening rate - about 200-300 °C/s. Therefore, even the slightest slowdown in cooling during hardening is unacceptable, since this can lead to partial decomposition of austenite at temperatures in the pearlite range and, as a consequence, to the appearance of soft spots. The decomposition of austenite occurs especially quickly in carbon steels at temperatures close to 500–550 °C, where it begins almost instantly, proceeds extremely intensely, and ends completely within a few seconds. Therefore, only tools of small diameter can be heated through and through after quenching in water. However, at the same time, large internal stresses arise in them, which can cause significant deformations. Tools that are large in size, when quenched in water and in aqueous solutions of salts, acids and alkalis, the cooling capacity of which is higher than water, are hardened to martensite only in a thin surface layer. The structure of the deep zones of the tools represents the products of austenite decomposition in the pearlite temperature range. The core of tools having this structure is less brittle compared to the martensitic structure. Therefore, tools with such a core can withstand shocks and impacts better than tools hardened through martensite. Carbon steels are most appropriately used for tools with a small cross-section (up to 5 mm), which can be quenched in oil and achieve through hardenability, as well as for tools with a diameter or minimum thickness of 18-25 mm, in which the cutting part is only on the surface layer, for example files, countersinks, taps. Carbon tool steels are tempered at temperatures not exceeding 200 °C to avoid a decrease in hardness. The hardness of a finally heat-treated tool made of carbon steels usually lies in the HB.C range of 56–64. The advantages of carbon tool steels are low cost, good workability by pressure and cutting in the annealed state. Their disadvantages are low cutting speeds, limited tool sizes due to low hardenability, and significant deformations after quenching in water.
We make a model knife from rapid steel
For those who are not yet familiar with rapid steel, I would like to explain why this steel is so good for making knives?
1. Rapid blades and discs are already hardened, that is, the blade needs to be cut and sharpened; there is no need for hardening.
2. High performance properties of rapid knives.
3. The widest range of applications. From forcefully scraping off paint, etc. from concrete to wood carving and other fine works.
Unfortunately, this steel also has its drawbacks.
1. Rapid is quite fragile - the price to pay for hardness. The father-in-law accidentally dropped the knife on the floor - the tip was gone.
2. Steel parts are processed using Rapid. Processing it this way takes a very long time. For example, it took me up to an hour to sharpen the blade.
3. Again, it’s easy to restore the rapid from a dull state to a razor; just a few correct movements on a whetstone or sandpaper are enough. And if you dull it well, you will have to spend a lot of time sharpening it again.
Well, now a short review of knife making.
1. At the flea market from Uncle Vasya (maybe Petya!) we buy a piece of mechanical saw. For thirty hryvnia (about three dollars) I bought a new mechanical saw 35 centimeters long. Then I found a couple more broken ones in my dad’s garage.
2. Use a grinder to saw off the required length from the saw blade. We don’t even try using a hacksaw.
2. On the cut piece we draw the outline of the future click
3. We clamp it in a vice and use a grinder with cutting and cleaning wheels to make a contour (don’t forget about the mask when working with the grinder).
4. Using a grinder or grinder (the latter is faster, but less efficient), we roughly form the slopes.
5. On a coarse-grained stone, we bring the slopes to an approximately decent appearance.
6. Take a hard, smooth surface, such as a cutting board, apply or glue sandpaper of the required grain size there, and moving the blade back and forth, bring the blade to the desired result.
7. If desired, you can polish it on a sharpener with vulcanite rubber wheels or felt with GOI paste. The blade is ready.
Now it's time to make the handle.
So, the options here are as follows, in order of increasing complexity and improving quality:
1. Don’t make a handle at all.
2. Wrap the handle with electrical tape (scotch tape), which was extremely popular in Soviet times.
3. Cover the handle with cambric (heat-shrink tubing)
4. Wrap the handle with rope, IV tubing, or something similar.
5. Plastic plumbing thermal pipe for hot water of suitable diameter. We clamp the blade with its tail up in a vice and use a mallet to fill the tube of the required length (initially we make the blade slightly cone-shaped). You can lightly sand the pipe - it will fit better in your hand. Not a bad pen for a short time.
7. Make a comfortable functional handle from wood, plywood, plastic.
Actually, I used the last two options. The first knife was made in the form of a model knife with a handle made of a thermal pipe,
the second is in the form of a shoemaker's with a beech handle.
The handle was made from two halves (beech), having previously made a cut in each using the device I described in the article “Another homemade mini circular or device for an electric sharpener”
The resulting workpiece just needs to be processed with a file to your liking. The result is higher.
The wood can be varnished or impregnated with linseed oil.
I wish everyone patience and perseverance when making a knife from rapid!
Decoding - what the marking symbols mean
Elements of equipment and devices have a high strength index, the material has excellent viscosity. Steel ensures long-term performance, both in product components and in blades or finished tools.
Such markings are a legacy of the Soviet era:
- The letter “P” is an indicator of high-speed steels. The expression comes from the translation of the English “rapid” - “swift”.
- The sign after “P” indicates the presence of tungsten in the composition as a percentage. For this particular metal it is in the range of 6% with minor deviations.
- This is followed by the letter “M”, indicating the presence of molybdenum in the stamp. The next indicator is the percentage of presence of the element in the total mass.
- In addition to M, high-speed steels can include the following designations in their markings: “K” - cobalt, “T” - titanium, “F” - vanadium, “C” - zirconium.
Considering the designation “P6M5”, decoding can also include other letters. If the steel was smelted by electroslag remelting, an addition appears in the form of “Ш” (Р6М5-Ш). With the introduction of the latest technologies into the production process, the following wording now appears - P6AM5. This means adding nitrogen to the overall composition.
Principles of alloying high-speed steels
The high hardness of martensite is explained by the dissolution of carbon in α-iron. It is known that when tempering from martensite in carbon steel, tiny particles of carbide are released. While the released carbides are still in the finest dispersed dispersion (i.e., at the first stage of precipitation when tempered to 200 °C), the hardness does not noticeably decrease. But if the tempering temperature is raised above 200 °C, carbide precipitation increases and the hardness decreases.
In order for steel to consistently maintain its hardness when heated, it must be alloyed with elements that would complicate the process of coagulation of carbides. If you introduce some carbide-forming element into steel in such an amount that it forms a special carbide, then the red-hardness increases abruptly.
This is due to the fact that the special carbide precipitates from martensite and coagulates at higher temperatures than iron carbide, since this requires not only the diffusion of carbon, but also the diffusion of alloying elements. Almost noticeable coagulation of special carbides of chromium, tungsten, molybdenum, vanadium occurs at temperatures above 500 °C.
Thus, red resistance is created by alloying steel with carbide-forming elements (tungsten, molybdenum, chromium, vanadium) in such an amount that they bind almost all the carbon into special carbides and these carbides go into solution during quenching.
Despite the strong difference in the general chemical composition, the composition of the solid solution is very similar in all steels, the atomic sum W Mo V, which determines the red resistance, is approximately 4% (atomic), hence the red resistance and cutting properties of different grades of high-speed steels are similar.
Where are high speed steels used?
The scope of wear-resistant metal depends on the composition that determines its working properties. Basically, this is a tool that has high demands on strength, heat resistance, and long service life.
- Production of drills, cutters, cutters, taps;
- Manufacturing cutting edges for tools, which in some cases can be removable;
- Parts for metalworking machines and equipment;
- Manufacturing of tools used for finishing hard-to-cut metal products.
Experts give the following recommendations on the use of these metal grades:
- Tungsten-molybdenum compounds are suitable for tools intended for roughing products, manufacturing cutters, broaches and shaver.
- Cobalt compounds are used for processing heat-resistant and corrosion-resistant products in difficult conditions.
- Vanadium alloys are used for finishing materials.
- The P9 grade is used to create equipment elements that are not subject to excessive load.
- Grade P18 is suitable for tools with complex shapes and shaped products with increased wear resistance requirements.
The range of metal products is represented by square, circle, strip, and sheet metal. Most often, cutting tools are made from a circle. Square steel is used for the production of electric planers, knives, and turning tools. If you have doubts about the correct choice of a suitable alloy, it is better to contact specialists. Specialized companies will be able to select high-quality rental products with the required performance characteristics.
Decoding - what do the marking symbols mean?
What is the meaning of the abbreviation R6M5 - spelling out steel? Such designations turned out to be a legacy of Soviet times.
The letter “P” is a designation for high-speed steels. The word is taken from the transcription of the English “rapid”, translated as “fast”.
The number behind the letter “P” indicates the percentage of tungsten in the alloy. For the brand described, it fluctuates around 6% with minor deviations.
Next comes the letter “M”, indicating the presence of molybdenum in the alloy. The next parameter is the proportion of the substance present in the composition.
In addition to Mo, high-speed steels may contain the following designations in their markings: “K” - cobalt, “F” - vanadium, “T” - titanium, “C” - zirconium.
Analyzing further the abbreviation P6M5, the decoding of steel may include additional letters. If the metal is produced by electroslag remelting, the nomenclature “Ш” (Р6М5-Ш) appears. With the introduction of new P6M5 technologies, decoding began to be found in this interpretation, P6AM5. This means alloying with nitrogen, which occurs at the stage of cooling the alloy after heating it to the hardening temperature (more details below). This steel is used in the manufacture of milling wheels.
Drill from Japanese company Nachi made of HSS steel
Imported analogues of high-speed cutters are labeled as HSS, which means High Speed Steel, literally translated, this is high-speed steel, and analogues of P6M5 are steels:
1.3343 (Germany DIN);
S600/S601 (standard D-016);
M2 (USA according to AISI/ASTM standards).
Decoding the designation of steel grades
Initially, high-speed steel as a material for the manufacture of cutting tools was invented by British specialists. Taking into account the fact that tools made from such steel can be used for high-speed processing of metals, this material was called “rapidsteel” (the word “rapid” here means high speed). This property of these steels and the English name he invented at one time was the reason that the designations of all grades of this material begin with the letter “P”.
The first number after the letter P in the designation of steel indicates the percentage content of such an element as tungsten, which largely determines the basic properties of this material. In addition to tungsten, high-speed steel contains vanadium, molybdenum and cobalt, which are designated in the markings by the letters F, M and K, respectively. After each of these letters in the marking there is a number indicating the percentage of the corresponding element in the chemical composition of the steel.
An example of decoding a high-speed steel grade
Depending on the content of certain elements in the steel, as well as their quantity, all such alloys are divided into three main categories. It is quite easy to determine which category steel belongs to by deciphering its markings.
So, high-speed steel grades are usually divided into the following categories:
- alloys containing up to 10% cobalt and up to 22% tungsten; These steels include alloys of grades R6M5F2K8, R10M4F3K10, etc.;
- steel containing no more than 5% cobalt and up to 18% tungsten; such steels are alloys of grades R9K5, R18F2K5, R10F5K5, etc.;
- alloys that contain no more than 16% of both cobalt and tungsten; These alloys include steel R9, R18, R12, R6M5, etc.
Determining the type of steel by spark
As mentioned above, the characteristics of steels classified as high-speed steels are mainly determined by the content of such an element as tungsten. It should be borne in mind that if a high-speed alloy contains too much tungsten, cobalt and vanadium, then due to the formation of carbide heterogeneity in such steel, the cutting edge of the tool that is made from it may chip under the influence of mechanical loads. Tools made from steels containing molybdenum do not have such disadvantages. The cutting edge of such tools not only does not chip, but is also distinguished by the fact that it has the same hardness indicators along its entire length.
The grade of steel for the manufacture of tools, which are subject to increased requirements for their technological characteristics, is P18. Having a fine-grained internal structure, this steel exhibits excellent wear resistance. Another advantage of using steel of this grade is that when hardening products made from it, they do not overheat, which cannot be said about high-speed alloys of other brands. Due to the relatively high cost of tools made from steel of this grade, it is often replaced with the cheaper P9 alloy.
Technical characteristics of steel grade P18
The fairly low cost of steel grade P9, as well as its variety - P9K5, which in its characteristics is in many ways similar to the high-speed alloy P18, is explained by a number of disadvantages of this material. The most significant of them is that in the annealed state such a metal is easily susceptible to plastic deformation. Meanwhile, P18 grade steel is also not without its drawbacks. Thus, high-precision tools are not made from this steel, which is explained by the fact that products made from it are difficult to grind. Good indicators of strength and ductility, including in a heated state, are demonstrated by tools made from P12 steel, which in its characteristics is also similar to P18 steel.
Properties of steel grade R9K5
Domestic quick cut (rapid) vs mainstream monsters
Eagle77 09/03/2021 — 13:06
Hi all. It would be very interesting to figure it out and understand how inferior our old domestic high-speed cutters p6m5, p18, etc. are. modern monsters of the mainstream!
Could you please clarify the evaluation criteria? What are you evaluating? RK durability, mechanics with the same hardness as monsters, something else?
And so far it turns out “There is an elderberry in the garden, and there is a guy in Kyiv!”:
They often cut meat with it right on the plate and constantly forgot to wipe it clean from water. To my surprise, the knife survived everything and didn’t even rust much, but knives from Rex121 and K390 instantly became covered with very unpleasant deep and pitting corrosion under much more favorable conditions
What does this show? That P18 rusts weaker than Rex and K390? How does this relate to cutting, durability of the paint and mechanics? No way! Let's get excited about 40X13! It is clearly better than P18 and all the others in general, because polished after maintenance it does not corrode at all!
