As a rule, buying a knife, a typical client must ask two questions:

1. From a steel knife?
2. What is hardness?

That is, even a layman somewhere in the depths of his soul understands that the glands are different and you can treat them differently. The latter, however, is obviously not for everyone.

Very often you can see in the statements such as forums, "I've bought a knife from 440B - complete shit about sausage crumbles on oil blunts." And then - "Yes, you're lying, I took apart his three wild boar, and everything is fine." In general, the degree of satisfaction of the user with a knife - the question is extremely versatile, but it includes the steel and its heat treatment. Which may be different. Sometimes much ....

So what is the heat treatment, and how to treat it?

Well, the name is already clear that this term describes a plurality of processing methods of materials based on the change of their structure (and therefore properties) under the influence of temperature. Often applied to the finished product all is often referred to as "quenching", although the actual hardening is only one of the stages. Sometimes, plaiting here still and hot deformation, all of this is called thermomechanical treatment, in most cases, is fundamentally wrong. Usually, the heat treatment includes several stages (sometimes - a few dozen). They all have different purposes and different modes. Confusion and adds that heat treatment in theory and in practice separate processes often have different names depending on the purpose and place in the technological cycle. Go into the jungle will not, we most important milestones and their regimes in terms of impact on the final result.

I think it will be easier to make it out as an example of a typical production technology blades (with an indication of the main technological processes) used by the overwhelming majority of World manufacturers. Consider a typical scheme used by masters-private traders and small-scale producer.

(forging)
1. Normalization (sometimes + high annealing)
(Cut blanks)
2. Annealing (or thermal cycling)
3. Hardening of the intercritical region
4. high annealing
5. Hardening
6. cryotreatment
7. The resulting vacation
(Rough grinding)
8. Leave after grinding
(Final sanding and finishing)

If cutting is done processing, there may be additional releases (or annealing).

Consider the effect of individual stages of the properties and quality of products.

1. Normalization (sometimes + high annealing) - allows you to bring the structure have become "common denominator" of which it is possible to dance on, relieve stress, grind grain, and in some cases remove the carbide grid or to receive the necessary treatment for hardness. Implemented as heating to temperatures above the phase transformation temperature (often up to temperatures causing significant dissolution of carbides) and still air cooling. Many began thus able obtain additional toughness and have high hardness - in this case, add a high holiday.

2. The annealing or thermal cycling - Allows you to grind grain, reduce the hardness to a minimum (for machining or cold working), to remove residual stresses. Is carried out by heating to a temperature slightly above the phase transformation temperature (in some cases - in the intercritical region) and slow cooling to the end of the decay of the pearlite. Often joke favorably replace thermal cycling treatment - multiple repetition of heating-cooling cycles at temperatures respectively higher / lower temperature phase transformations. This treatment allows considerably more grind corn and as a result get a much better fur. characteristics.

3. Hardening of the intercritical region. Can significantly reduce the leashes and warping of parts due to the closure of the micropores in some cases slightly increases the hardness and fur. characteristics of steels. Performed as a "soft" hardening of the intercritical region, usually oil cooled.

4. High annealing (from the point of view of the theory of heat treatment - subcritical annealing) - relieves stress after fur. processing, preparing the structure of steel to quenching, in some cases, reduces the hardness of the steel to a minimum.

5. Hardening - The main stage of heat treatment. It is heated to a temperature above the phase transformation temperature and tend to cause a significant dissolution of carbides, creating the desired saturation of a solid solution of carbon and alloying elements and rapid cooling (at a rate above the critical value), fixing the supersaturated solid solution.

6. cryotreatment - cooling products to low temperatures (typically -78 - 196 C). It pursues the aim of the fullest possible transformation of the residual austenite, thereby increasing hardness, resistance to buckling and reduce the risk of transformation of austenite during operation, but may reduce the viscosity.

7. The resulting rental - forms the final properties of the blade. Usually done heating to relatively low temperatures (sometimes average temperatures). When the secondary hardening hardness of commonly used multiple heating to temperatures of active precipitation hardening and transformation retained austenite.

8. Leave after grinding - relieves stress and sometimes Shlifovochnye stabilizes austenite formed during grinding.

Not all steps are not always necessary, some may be partly or completely replace each other - it all depends on the steel and the technological cycle. In the case of the purchase of semi-finished noticeable part of the thermal treatment has already been done in the enterprise - manufacturer.

Typically, thermal treatment is divided into steps, and the resulting preliminary heat treatment. The resulting thermal processing forms properties of the finished product (as a rule, it is all from the last high-level - hardening), the task of preliminary heat treatment - to provide the necessary technological properties and to prepare the structure to the resulting heat treatment.

Naturally, it is the resultant heat treatment of the most severely affect the "basic" properties of the steel, but it is a preliminary thermal treatment often allows you to "squeeze" out of steel a maximum of what it can do.

Naturally - free cakes does not happen. With the increasing complexity of the heat treatment of heat treatment are growing labor costs, loading equipment, etc. That inevitably leads to an increase in prices of products. Often repeated. Therefore, it is too optimistic to look for diamonds among consumer goods. On the other hand, attempts to make the most can lead to cost such that the product acquires a status of "exclusive" with a corresponding price. We must stop somewhere. Where exactly - each manufacturer decides for himself. More precisely - where it stops target buyer.

Consider the basic options.

1. Bound, heated in a furnace to bright orange, put it in the oil. Held it over the coals 5 minutes - you're done ... In this case, count at least on average for this was the result of a fairly optimistic. With vast experience, everything is possible ...

2. Gave "what the treater" a defense plant. What and how is he doing with a piece of iron - this is the great mystery ... The result - of the total sludge to very good, but with a marked predominance of the first. Cadres decide everything.

3. There is a stove, there is a "guide", has a strip of high-quality steel. Knowledge and understanding of why and how - no. If particularly strong kosyachit not, then it is likely to get a good result. Especially with modern steels - they are usually quite tolerant to errors.

4. The same + minimum idea of ​​what, where and why. As a rule, the accumulation and understanding of their own and others' experiences and personal responsibility may receive consistently good results.

5. There is a clear idea about the subject and / or a great personal experience. Plus interest in the result, and personal responsibility. This preconditions to obtaining sustainable results significantly above average. Copyright schemes often allow thermal processing of steel to squeeze much more than what is expected of them.

6. Blades - champions also require a certain amount of luck.

Consider the basic error during heat treatment and their impact on product quality.

1. Lack of hardness - usually a consequence of subcooling quenching (rarely - overheating) or excessively high tempering. In mild forms found on inexpensive knives as a compensator overly simplified heat treatment.

2. The excessive hardness and brittleness. And here is more complicated. Often it is not a high hardness, and overheating during hardening, the steel gets too large grain. Actually, the hardness is not the only indicator of a quality - for the same hardness can come in different ways and with different results. So statements like "knife above 58HRc fragile as glass" should be taken with a robust skepticism.

3. Decarbonized layer. In the absence of protective atmospheres / or vacuum coating equipment is almost always present. Etching usually looks much brighter than the background. With proper planning, process technology, this layer is removed, but in some cases (for example, by quenching the workpiece finely information or perform with a knife "single bevel or japan" sharpening without removing the decarbonized layer) it can go to the Republic of Kazakhstan, with the sad consequences for the latter. Sometimes it can cause errors in the determination of hardness - where it will be much smaller than the body of the blade and the ROK.

4. Cracks. There may be at different stages of production, the most common forging, hardening or grinding. They are by far the incorrigible marriage. Sale of the blade (except in very rare cases, to multi-layer blades or Damascus) - a direct reference to the manufacturer's attitude to business. Shitty attitude.

5. Leads and warping. On the Long-they are virtually inevitable, in a short blade are permitted to a certain extent.

In conclusion, a few real-life stories about different knifemakers.

1. Through hardening smith "A" make-up the several dozen pieces pins, throws into the furnace, is to drink vodka. A few hours later comes back, throws a "sandwich" in the tank with oil, is to drink vodka. Annealing does not - and why, and so there is 58 HRc...

2. Smith "B" in hardening D2 with temperatures at 50 degrees over the years above the optimum. To ask the question about the reasons - "I always do, people do not complain."

3. Enthusiast "B" decided to hold cryotreatment by quenching a hot billet to 1175 in liquid nitrogen. On offer at first find the value of the heat of evaporation of liquid nitrogen after two days thoughtfully expressed "f**k."

4. Smith "T" hardening each workpiece differently. At the same time he does not feel them, and ratings are not systematically collected. Seeking a own way ...

5. Master "D" of the blade during quenching EACH addition to the author's heat treatment and testing for hardness always controls the break - just in case. That is - the application for the responsible attitude that manifests itself in other matters, and is reflected in the price of products.

So, choosing a heat treatment you choose MANUFACTURER. Different masters may be different views on the heat treatment, but a responsible and reputable manufacturer and the consumer never released a product with the properties below a certain minimum. And in the case of marriage (which is not the case) will make every effort to resolve the situation.