K390 steel for knives: advantages and disadvantages of the alloy

K390 steel from the Austrian company Bohler is considered one of the best for making knives and other cutting tools. It is a tool powder steel intended for the production of stamping tools by cold deformation. It is used mainly for the manufacture of folding and hunting knives.

It is usually not used for the production of kitchen knives due to its high cost. This metal is used to make knives of a higher price category. But, like other types of steel alloys, the material has its advantages and disadvantages.

Features of the K390 alloy
K390 steel is characterized by increased hardness, strength and wear resistance. It is a high-speed steel with high toughness and resistance to mechanical wear. The special chemical composition provides high hardness of the material, thanks to which the cutting edge of the blade retains its sharpness for the longest time, even under harsh operation.

Currently, the brand is considered one of the best tool steels for cutting tools on the market. During the production process, a homogeneous carbide structure is formed, which guarantees maximum hardness and wear resistance.

It has the following chemical composition:

Carbon (C) – 2.5%. Provides hardness, wear resistance and toughness. Due to the high carbon content, the edge retains its sharpness for a long time.
Chromium (Cr) – 4%. Increases density and tensile strength. Provides protection against corrosion, but in this case insignificantly, since the chromium content is low. Slightly increases hardness.
Molybdenum (Mo) – 4%. Increases strength, hardness and annealing. Promotes protection against corrosion.
Silicon (Si) – 0.55%. Deoxidizes steel and increases strength.
Vanadium (V) – 9%. Improves toughness and strength. Increases resistance to abrasion and rust formation.
Tungsten (W) – 1%. Increases toughness, strength and annealing. Does not change hardness under the influence of elevated temperatures.
Cobalt (Co) – 2%. Increases hardness and strength. Allows hardening at elevated temperatures. Enhances the positive properties of other elements.
The HRC (Rockwell hardness) of this metal varies in the range of 62-66 units. This is one of the best indicators on the market of steels for the production of cutting tools. Due to this hardness, the cutting edge retains its hardness for the longest possible time. At the same time, it is quite difficult to sharpen such a hard alloy with household tools.

The material is relatively expensive, so premium knives are made from it. At the moment, the steel provides the maximum possible resistance of the cutting edge to abrasive wear. At the same time, high resistance to chipping and good impact strength are maintained.

Advantages of K390 steel
The main advantages of the Bohler K390 alloy include:

• Increased resistance of the cutting edge to abrasive and other mechanical wear. The closest analogue in terms of this characteristic is the CPM 10V brand, which was previously considered the standard, but was inferior to K390 in other parameters.
• Increased impact strength due to the presence of sufficient amounts of molybdenum, tungsten and cobalt. According to this characteristic, the metal is 1.5 times higher than CPM 10V.
• Good grinding and polishing properties. This allows deep scratches and other stress concentrators to be removed from the surface. The blade and cutting edge can be given an almost mirror-like shine.
• Increased compressive strength. This allows you to make all kinds of stamps, dies, band knives and other parts.
• Resistance to chipping. This ensures reliability and long service life of finished products.
• Homogeneity of the structure. Thanks to this, the characteristics are stable across the entire area of ​​the blade.
• High hardness – 62-66 HRC. Even with intensive and harsh use, the sword remains sharp for a long time.
• Resistance to overheating during heat treatment. Steel withstands prolonged heat treatment without deterioration of properties, which guarantees high-quality hardening and annealing.
• The ability to manufacture blades by forging. This allows craftsmen to produce unique collectibles.
• The possibility of further improving performance during the manufacturing process of finished products. For example, some manufacturers perform additional heat treatment using multiple thermal cycling and cryogenic treatment.

Large knife with K390 steel

Disadvantages of the alloy
Despite the huge number of positive characteristics, the material has some disadvantages:

High cost. Knives of the highest price category are made from this steel. It is used by large manufacturers. Although some private craftsmen produce products from this alloy in small batches. For the production of kitchen knives, as a rule, enyaets is not used.
Low resistance to corrosion. The composition contains quite a lot of carbon and little chromium, so the material can rust. This is a kind of payment for maximum hardness. Therefore, the knife requires proper and regular maintenance.
It is quite difficult to sharpen the edge yourself. The steel is very hard, so it is difficult to sharpen. To do this, you need to use special sharpening tools, such as diamond and elbor blocks. The complexity of sharpening is one of the secondary factors of the high cost of finished products.
Risk of injury. When sharp, a knife cuts itself very easily, so you should work with it carefully.
A small selection of models. Only some large manufacturers and private craftsmen make knives from this alloy. At the moment, the company offers the largest number of models

Conclusions and advice
K390 steel is deservedly considered one of the best tool alloys on the market for the production of cutting tools. However, products made from this material cannot be called a good choice for everyone. Knives with K390 blades are quite expensive, and the choice of models is small.

Large companies produce products in small batches, and individual craftsmen often produce only to order. Therefore, such products can be recommended to professionals who are familiar with steels and the features of their operation. Such a blade must be properly cared for, otherwise it can become covered with rust and pitting, which often affects not only the appearance, but also the performance characteristics.
A knife made of K390 should be used carefully, since a damaged edge will be expensive to restore due to the difficulty of resharpening. Otherwise, K390 is an excellent powder steel for making high-quality premium knives.

It is worth remembering that if you use the knife for its intended purpose and treat it with care, it will last you a very, very long time.

Sperm whale

Sperm whales  are typical representatives of cetaceans. They originated 70 million years ago, either from some predatory animals or from insectivores. Today, all connections with terrestrial life have been lost, and their adaptation to aquatic life has remained remarkable.

The sperm whale's body is hairless, almost smooth, with a very thick layer of subcutaneous fat, which serves as a thermal insulator. A few bristles have survived only on the snout. On the lower jaw there are 18-30 pairs of teeth without enamel, the largest of which weigh almost 2.6 kg each. The pectoral fins are wide and bluntly rounded. The body color varies from grayish-brown to black-brown.

A very large stomach  - holds more than 500 liters of liquid. The kidneys are twice as large as those of land animals, because they have to remove a large amount of salts from the body, which come with sea water.  The length of the intestine  is about 160 meters, but its structure is extremely simplified. The first riddle: why does a carnivorous animal have such a huge intestine?

There are other inexplicable phenomena associated with the sperm whale. For example, why are its nostrils not directed upwards, like all whales, but obliquely forward?

It is known that sperm whales can stay underwater without air for more than an hour, and go to a depth of more than 1200 meters. The paradox is that sperm whales have smaller lungs than other whales, and they have to hold their breath for a long time... So, here is another mystery.

The sperm whale  is a real giant. It is born four meters long and grows very quickly to 18 meters. An old sperm whale weighs more than 50 tons, others under 100. Among sperm whales there are also real babies. For example, the dwarf sperm whale (Kogia breviceps) or kogia has a dolphin-shaped body 2.4-3.3 m long (males are slightly larger than females), weighing up to 300 kg. These cetaceans live in the warm zone of the ocean and are very rare.

Sperm whales swim in all oceans except the Arctic. In the summer, they migrate from the subtropics to cold waters and swim into the Mediterranean and Baltic Seas. They can often be found off the coast of West Africa and Japan. Sperm whales are the only ones that cross the equator during migration.

The sperm whale feeds on cephalopods (80%) and a small amount of fish (spiny sharks, sea urchins, pollock, cod, saury, bullheads). It can hunt very large cephalopods (squid). Mollusks up to 18 meters long have sometimes been found in its stomach. Hunting for them, the whale dives hundreds of kilometers.

Sperm whales have no sense of smell, poor eyesight, but excellent hearing. Studies have shown that sperm whales communicate with each other using signals, and navigate in space and find food using echolocation (similar to bats).

The sperm whale is considered a dangerous animal for humans. But what is this danger if it does not specifically hunt people? There can be two reasons: it attacks either out of fear or out of revenge.

In 1820, a furious sperm whale rammed the Essex twice. The ship weighed almost 5.5 tons, but the whale was able to sink it. Only a few people survived. Small wooden vessels, weighing as much as a small whale, often suffer from such rams. What can we say about small fishing boats ...

Sperm whales can swallow people whole without chewing them. The schooner "Star of the East" caught a sperm whale, and when it was cut open, three whole human skeletons were found. It is not difficult to imagine how painful the death of these poor creatures was, because they were digested alive.

Tragedies most often occur when a sperm whale is frightened. Then it begins to defend itself and attack. It mistakes large boats with people on them for large animals, which is why it attacks them.

In addition, we must remember the existence of whaling ships. If a sperm whale manages to escape once, after that it will be hostile to any boat with people. I think you have already seen what power this giant has, so you only have to guess about the fate of the ship that the sperm whale decides to attack.

Length: up to 18 meters

Weight: more than 50 tons

Habitat:  swim in all oceans except the Arctic.

Danger!

It often rams boats. It swallows people whole.

Mammoth tusk  is a precious material, however, due to its ancient age (which is at least 10,000 years old), it has not been preserved in good condition. This is primarily due to the place where it was extracted, the best protection is provided by tusks extracted from permafrost, which serves as an excellent "refrigerator for tusks", in which the tusks can be preserved in almost their original form.

The worst preserved tusks are those taken from rivers, they usually have a lot of cracks. If the tusk has been lying somewhere on the surface, it will most likely not be suitable for carving at all, since under different weather conditions with temperature and humidity changes, tusks are very damaged over time. Due to these factors, the appearance of cracks in tusks is a natural process, which is sometimes inevitable even under artificially created favorable conditions.

Mammoth tusk can also take on different shades as a result of mineralization, depending on the composition of the soil where it has been deposited for thousands of years. The range of shades is very wide: from light cream to brownish black.

 

By the way, about 10 tons are mined annually in Yakutia alone, which is one of the largest mammoth burial grounds. According to experts in the North Yakutia province, potential resources could be up to 450,000 tons.

 

Only the first and second grades are considered suitable for sculptural carving. In total, mammoth tusk is conventionally divided into five types of grades:

• Collectible
• First grade
• Second grade
• Third grade
• Fourth grade

Collectible tusk

The most valuable is the mammoth tusk, which is completely preserved, has no external damage, they are from 1 meter to 3 meters and longer in length, such specimens are especially rare. As a rule, collectible tusks are rarely used for bone carving, they themselves are very beautiful and are transferred either to museums or used as interior decorations. Paired tusks of one animal are especially valued, their size also plays an important role. It should be noted that such tusks are not always of high quality inside, their main value is excellent external safety, sometimes such a result is achieved through skillful restoration. There are cases when two specimens are combined to give a tusk a larger size, usually this is the whim of the customer.

 

 

First grade mammoth tusk

This grade is most valued for sculptural carving, it includes whole tusks, as well as well-preserved fragments of tusks that do not have cracks or other visible defects inside, the presence of one annular crack of a small thickness of up to 1 cm is permissible, this is peeling bark (it is present in almost all tusks now, with rare exceptions). A mammoth tusk of the first grade must have a diameter of at least 10 cm, but the larger the diameter, the higher the tusk can be valued. The fragments must be dried and at least 35 cm long.

 

Second grade mammoth tusk

It can also include specimens that are whole or fragments that are well preserved, but have no more than one crack on the end cut. The second grade can include dried tusks that have cracked into two halves or have no more than one annular crack and do not have significant internal defects, at least 20 cm long. This grade of mammoth tusk is quite suitable for making small sculptures. This material is also highly valued, although in terms of cost, such material is significantly cheaper than the tusk of the first grade.

Third grade mammoth tusk

This type of raw material for bone carving is valued much lower; the solid mass of the tusk inside is much smaller, as it can have two or more cracks, up to 10 cm long. However, the best specimens of this variety are also suitable for carving small sculptures.

Fourth grade mammoth tusk (cod)

Such material is considered inexpensive and unsuitable for sculptural carving, it usually has many radial and longitudinal cracks and is suitable mainly only for the manufacture of small products, mainly jewelry (brooches, pins, pendants, etc.). It can also be used for the manufacture of caskets, knife handles, decorative screens and as additional elements in carved sculptural compositions, if they require it according to the artist's plan.

 

Microcracks that form later on the sculpture.

It is interesting that fresh microcracks that sometimes appear on finished products can completely heal with prolonged changes in air humidity, and then appear again. This process is difficult to predict and almost impossible to control. Such cracks (craquelure) can often be observed on antique works made of ivory or mammoth bone. Such craquelure does not in the least diminish the artistic value of the work, and sometimes even adds a certain charm, as if speaking of the antiquity of the material from which they are made.

Mammoth tusk storage

It is necessary to remember about the age of the mammoth tusk to avoid cracks. It is necessary to store it following certain rules. from the ends with PVA glue, this will prevent the appearance of new cracks during drying. It will be even better if the tusk is tightly wrapped in a cellophane bag and stored in this form.

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Asian buffalo

This is one of the largest animals belonging to the bovine family. The body length reaches 3 m, the height at the withers is 2 m. Large males can weigh a ton or even more. The horns of these animals are in the form of a crescent moon, directed in different directions and slightly backward.

The color of the animals is gray. The wool is thin and moderately long. On the forehead it forms a small tuft. The body of this animal is massive, powerful, the limbs are strong, muscular. The hooves are large and cloven.

The head resembles a bull's, with a more massive skull. The eyes and ears are small. The tail is thin, long, with an elongated tuft of hair at the bottom.

African buffalo

It is slightly smaller than its Asian relative. Its height is up to 1.8 m at the withers, its body length is 3 m. It weighs slightly less.

The African buffalo is black or dark gray in color. This animal has pronounced sexual dimorphism: females are much smaller than males. Females also have a less powerful physique. Their horns are shorter and thinner.

The African buffalo has unique horns. Their bases in adults are fused, forming a kind of shield of bones. It is so strong that a rifle bullet cannot pierce it. The horns at the base diverge to the sides, bend down, and then with the same smooth bend go up and inward. Young individuals do not have such a shield of horns.

The African buffalo has very poor eyesight. It receives information from the world around it through its highly developed sense of smell and hearing.

In normal circumstances, the animal roars and snorts. In extreme circumstances, it moos loudly.

Lifestyle

The buffalo grazes at night. It spends the day in the shade of a tree, in a swamp, where the temperature is lower. It sleeps or chews gum. Often a puddle or hole can be a shelter from the heat. It needs a daily watering hole. During the day, the animal needs up to 40 liters of water. In this regard, the buffalo never moves further than 4 km from water.

Females with calves are especially sensitive. They are constantly on the alert, showing their anxiety. When alarmed, the buffalo raises its head and throws back its horns. A quiet sound is enough for the herd to flee from danger. In case of serious danger, the animals can reach speeds of over 50 km/h.

Buffaloes are reluctant to enter the water. However, they are good swimmers.

Buffalo habitats

Back in the 19th century, this animal was common in sub-Saharan Africa. Today, buffalo populations can be found in Southern and Eastern Africa, where human interference in the biosphere is least noticeable.

Buffalo can live in savannahs, tropical forests, mountains (up to a height of 3 km). The animal feels best in savannahs, where there is year-round access to drinking water and juicy food. Buffalo does not live far from water bodies. Due to human extermination, the animal is most attached to protected areas: there you can meet herds of hundreds of individuals.

Demeanor

In the north of Tanzania there is a national park near Lake Manyero. It is here that the largest population of these herbivores is found. The animals are attracted by the spacious pastures located in the green zone between the lake and the mountain slopes. Some adult bulls do not associate their lives with the laws of the herd, preferring an independent existence. The large size and large strong horns are a sufficient reason to feel safe.

Important decisions for the herd are made by high-ranking females, and controversial issues are resolved in the form of a special form of voting. Closer to lunch, the herd settles down to process the morning feed. Sometimes the leading females raise their legs, turning in the direction, while the others carefully follow them. As a result, the herd moves further in the direction chosen by the "majority of those who voted."

At this time, it is time for procedures related to personal hygiene. Local species of woodpeckers and herons are happy to provide their services in cleaning the skin, in exchange for insects collected under the fur. Thus, the birds help the buffaloes regulate the populations of parasitic insects capable of carrying pathogenic microbes. The immune system of an adult buffalo allows it to cope with almost all common diseases. However, weakened individuals can become victims of parasites.