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SECRET OF MANUFACTURING BULLETIN STEEL

Blade material - hardened steel - has the property that hardness and its elasticity within certain limits is in inverse relationship. The hardness of the blade should be large enough so that the knife does not quickly become blunt, but not excessive, otherwise the cutting edge will break out or the blade will break.

It has long been noted that the durability (wear resistance) of the blade does not necessarily depend on the hardness of the blade. Quite often, at what time a soft blade was duller in labor less than the more cruel. At the Zlatoust factory known metallurgist Anosov, trying to restore the secrets of the technology of manufacturing damask steel, determined the wear resistance of the blade by cutting felt rolls. In the course of the work it was found out that the samples of blades, taken from one piece of steel, also passed the same heat treatment, have different characteristics.

Cutting properties of the blade are determined by the parameters of the micropyle that is formed when it is sharpened, also visible if you look at the edge of the blade under the microscope. The teeth of this saw must be small and the same, their peaks should have the maximum hardness and not be dyed. This is ensured by the microstructure of the material also by the method of sharpening the blade. The sharper the angle of sharpening, the more easily the blade slips into the material being processed. But since the thin blade is more fragile, in order that it does not break in any way, it is necessary to increase the elasticity, thereby reducing the wear resistance.

In antiquity, the optimum combination of these properties was provided by bulat - the material that was brought from India. In the countries of the Near East, it came in the form of ingots, and then, in the process of forging, also hardening by special methods acquired unique properties, combining high hardness and greater elasticity compared to those who did not possess similar qualities, in our understanding, ordinary blades. However, the damask also were different. At the end of the last century, at what time, once again, interest in the technology of manufacturing damascus broke out, a commission was established in Russia that took into account all the samples of bulat weapons that were available in the country. Thus, half of the collected almost 4,000 blades turned out to be a forgery, but among the others only one percent had outstanding properties.

Damascus is a material (steel, as it were reinforced with more elastic fibers), obtained as a result of the forging of slightly high-carbon strips into one monolith by special technology. Damascus and damask are often confused, since on both materials, when etched, a pattern appears showing the structure of the metal. And yet they are different in percentage of carbon content.

According to the carbon content (in a special crystalline form), bulat occupies an intermediate position between the high-carbon steel and cast iron, but in Damascus its essence is the same as if it were also in carbon steel. Low-carbon Damascus went for the production of hunting rifle barrels, which, with some exceptions, were much more expensive than steel ones, as if manufacturing a damask was a more labor-intensive process.

Now the production of blades is experiencing another boom in the revival of the tradition of making patterned steel. Most of the respectable foreign firms, of course, and many private manufacturers, as it were in Russia, as well as in the far abroad, have restored the production of damask blades, as far as I understand, using mainly the decorative properties of the material. New, previously unknown combinations of materials have been created in Damascus, for example, stainless Damascus. From time to time in the press there are reports that in various ways it was possible to get also bulat steel, but its industrial production is established only at the Ukrainian NGO "Bulat" (Zbroya ta Poluvannya, 1999) . Moreover, damask knives, which are used, for example, in the manufacture of plywood, cutting paper, preparing chips for paper production, also the production of particleboard have a higher ordering stability than similar knives from the best Swedish steel.

Later, the correct forging, hardening, grinding and etching in the damask blade shows up a characteristic pattern that does not repeat itself (in damask the pattern consists of repeating elements). Even with the hardness of HRC 36-40, such a blade can not be sawed with a nail file, which is well scraped by steel, hardened up to HRC 54-56 . The disadvantage of bulat is its predisposition to roasting. There is evidence that a stainless steel bulat has already been obtained, but is it bulat?

In its time in Russia there were other excellent blade steel. For example, Daggers also used Egor Samsonov's knives from Tula in great popularity in the Russian Empire. Many of its products are included in all pre-revolutionary catalogs of hunting stores. The entire technological chain, from steel smelting to heat treatment, but similar to the finishing of knives, he produced on the building. Samsonov died already at the time of Soviet domination, he did not leave any disciples and did not pass on the secrets of his skill to anyone. They say that at what time he was already weak, he turned to the rulers with a petition to help in the repair of the building, as if he had neither the strength nor the means, but for this he promised to tell about all the intricacies of dressing his steel. But the Soviet authorities did not respond to the injunctions of the dying person, and the means of manufacturing such steel was lost.

In the 50's and 60's at the Moscow plant "Sickle and Hammer" attempts were made to restore the technology of making Samson knives, yet they ended in vain.

In our time in knife manufacture apply more than hundred grades of steel. Among them there are materials possessing unique properties, although they are also quite expensive. So, the units of US sea saboteurs - "Seals" are armed with combat knives, which can shred steel mesh, while not completely damaging the blade. Of the ceramic material - zirconia (zirconia), blades are made, but titanium nitride (golden color), titanium carbonitride (black) or alternating them are used as the coating of the steel blade. Another time, the blades are also coated with a diamond-carbon film. These coatings act on the surface of the blade extremely hard, but still it is, so to speak, exotic. Basically, modern knives are made of stainless or - on the fan - carbon also alloyed steels.

The blade of a damask knife, depending on its make-up, is five times, and sometimes also ten, more expensive than usual.

Favorite brands of steels used by foreign manufacturers are 440С , АТС34 , 154СМ (according to some data, steel АТС34 also 154СМ differ in the occurrence of non-basic alloying elements - manganese also silicon). The cast steel D2 appeared about ten years ago. It has a unique microstructure (with special heat treatment), which allows grinding with a small angle at HRC 58-60 . Steel CPMT440V , which is close in composition to the bulat, is produced by powder metallurgy. Firms guarantee firmness, but it does not mean that the blades made of such steel are not deficient.

My colleague brought a knife from the US, released by one of the oldest firms in the universe - the firm Buck. Certified quality certificate guaranteed the hardness of HRC 60 . And indeed, after testing the blade from 450C steel on the Rockwell instrument, we saw for ourselves. The knife was sharpened to the razor sharpness (although it was also sharp enough up to that) manually with the use of a special liquid (in order, God forbid, to let go of the edge) using a Lansky type device. However, on the first catch, the edge was safely jammed on a common fir bough.

Cheaper knives foreign firms operate from simpler steel, on which there are conventional brands 420 , 440 , 440A or simply indicating that this is stainless steel - INOX , ROSTFREI , SINOXID . They are hardened up to HRC 50-54 , and they are no better than wear table knives, so sharpening the edge at an acute angle is absolutely not necessary. Somehow I got a knife from the GDR, so far we have not even found out what material it was made from. So, when it was sharpened on the circle, there was almost no sparks, only rare red liquid threads. We could also sharpen it, the burr did not break in any way, although the blade was very hard.

Among the "Soviet" steels in place of the former manufacturers of consumer goods of carbonaceous also alloy steels of the type U7-U8 , 65G , 60S2 , ShKh15 , 9KhF , X6VF , etc., which are also very popular among handicraftsmen . Now the "stainless" steel type 40X13 , 40X13NV is quite common . These structural steels are now no less "loved" among craftsmen, hundreds of them work on every PTO or giant plant.

Some virtuoso virtuosos in quenching such steels have achieved really good results, reaching hardness of HRC 56-58 at a satisfactory elasticity. Cutlery is also used from similar steel. Having examined the data of the table, we see that its closest analogue is steel 420 (unless the essence of manganese is somewhat higher). Despite the fact that this steel is called stainless, it is actually susceptible to corrosion, especially in an aggressive environment or with low polish quality.

The composition of some foreign steels used to make knife blades
(Based on foreign periodicals)

Less corroded is steel 95X18, which contains 18% chromium and also approximately "reaches" up to 440C (closer to 440V ). This is a truly remarkable steel plus, naturally, more expensive. However, it is only possible to obtain such properties if the technology of forging and heat treatment is carefully observed. Today, only solid, well-established firms can provide such heat treatment conditions - heating in vacuum furnaces with high-precision temperature control, long-term tempering, cryogenic finishing (holding at low temperatures to produce extra fine grains). But the handicraftsmen, in no way observing all the subtleties of the technical process, will not be able to get good results, and it turns out that the quality of the knife from 95x18 is not any better than that made of steel 40X13 also hardened by a master virtuoso. Some of Russia's factories make some of this steel. Mention is similar to "diversionary steel", from which, perhaps, did "knives scouts" of the Soviet Army. I have seen a similar knife. His handle was literally soaked from misses when throwing at the target, but the blade is slightly blunt on the blade, of course, also only because, as the owner of the knife said, at a miss, he constantly got into the concrete fence. Steel 65X13 (similar to the Swedish 13C26 ) with good quenching is one of the most suitable materials for a hunting knife, as if the hardness of HRC 54-56 is sufficiently elastic and wear-resistant.

Another time local craftsmen make good blades even from artless low-carbon steel, sprinkling a strip of pig-iron crumb during forging. The metal strip is forged, repeatedly folding it. Carbon, contained in cast iron, diffusing into neighboring areas, turns them into steel. It turns out something like a damask. Naturally, a good blade can be obtained, only having a large experiment of labor is also a "flair" of metal.

In mass production, the strip of knife (blade) is made by hot stamping, with artisanal cutting of sheet material or by forging from a rod. They say that the wrought blade is stronger - maybe, but at the subsequent processing stages, the recrystallization of the part results, and this additional citadel is lost in many respects, unlike the riveting in the quenched state, for example, braids, shovels, where such fretting is significantly Improves the properties of the material. At handicraft production, the billets from 95X18 can easily be damaged if the forging heat regime is not observed. Later heat treatment of the blade follows the final grinding, finishing and sharpening of the cutting edge. Usually the angle of convergence of the chamfers on the strip of blade that form the blade is less than the angle of sharpening of the cutting edge - it is easier to provide quick grinding of the cutting edge, it is especially convenient to sharpen the blade with a profile that is concave in cross section. The angle of sharpening for different kinds of work varies. For example, 8-12 ° for razors, 10-15 ° for skins, 12-20 ° for hunting knives, 20-30 ° for woodwork (chisels, axes), 30-45 ° for cutting Raw bones, 40-60 ° in sabers.

Cutting nails, punching barrels for gasoline (as some companies do for advertising purposes), even opening cans without damage to the blade is possible only at the angle of sharpening, which corresponds to this "work" - 55-65 °. When cutting blades, a friend about a friend will gain the advantage of the wrong knife, which is made of higher quality steel, but to the one with more grinding angle. A sufficiently long blade can own several sections with different angles of sharpening the cutting edge along the length.

Falshlesvie, in contrast to combat knives, should not be sharpened in any way, since it only hinders the opening of the peritoneum, but it can be used in cutting, releasing from this labor a thin base blade.

Near the heel, a large angle of sharpening is often done to perform heavy work, or they use for this purpose a section with a so-called serretor sharpening - a wavy sawtooth sharpening consisting of identical or alternating more or less bottomless grooves that run across the cutting edge. There are a lot of options for this kind of grinding, besides, the blade with such sharpening is very effective when working with hard parts of muscle tissue, cartilage, tendons, ropes (parachutist strop cutters). Old Finnish knives are also knives, the blades of which gradually thin to the point, have a variable angle of sharpening (the plane of sharpening is twisted by the propeller on each side). Some northern peoples of Russia traditionally use knives with one-sided sharpening.

For the finishing of modern blades, the manufacturing companies use the electropolishing method also the fashioned fine grinding of the metal.

In order to camouflage military knives often tinted. The hunting knife is enough only to polish the blade to improve the anticorrosion properties of the metal, as well as to lessen the filling of the blade when cutting the trophy.

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