ES2347255T3 - COLD DEFORMABLE CHROME STEEL. - Google Patents

Abstract

Chrome steel consisting of 14% to 20% chromium from 0.005% to 0.05% carbon to 0.01% nitrogen from 0.2% to 0.6% silicon from 0.3% to 1, 0% manganese 0.1% to 1.0% molybdenum up to 0.8% nickel 0.2% to 1.0% copper 0.02% to 0.2% selenium 0.01 % to 0.1% arsenic as well as individually or together with each other from 0.01% to 0.1% lead from 0.01% to 0.5% bismuth from 0.01% to 0.1% antimony 0.005% to 0.08% vanadium 0.005% to 0.08% titanium 0.005% to 0.08% niobium 0.005% to 0.08% zirconium 0.15% to 0, 65% sulfur up to 0.20% tellurium, and the rest, including impurities caused by fusion, iron.

Description

Cold deformable chrome steel.

The invention relates to a chrome steel cold deformable with a ferritic texture.

The ferritic chromium steels, deformable in cold and stable against corrosion, without the application of special technical measures of alloys, have a bad machinability by chip removal, which should be attributed to some adhesions and welding contributions, which result in machining with chip removal in the edge region tool treble. The consequence of this are some rashes and crumbling on the cutting edge or respectively a high wear of the tools, and also a poor surface quality of the treated work pieces.

In the case of embossing tools and conformation, such adhesions and welding contributions they also have a very disadvantageous effect, since they they appear preferably precisely in the region of a high surface compression, and there they worsen the surface quality of Shaped work pieces. In addition, they shorten the period of time in useful state of the tools. Apart from a machinability by chip removal and workability (roughness) good, steels require a certain minimum mechanical resistance, which can only be achieved by certain components of the alloys that, like the titanium, vanadium, niobium, zirconium and molybdenum, form carbides or carbonitrides. These are presented in texture as hard and hardly soluble segregation phases, and tend to enrich the texture locally, and to form in this way agglomerates, nests or structures in the form of lines.

This is linked to the danger that, in the case of microtreatment, for example when producing drills, slots and recesses of small and very small dimensions, due to the local concentration of hard segregation phases is reach a tool tip, for example, from a drill drilling machine, and accordingly, to considerable deviations in the final dimensions. This must be attributed to the fact that treatment tools, for example, drill bits with a small diameter, they tend to depart from regions that they have a higher hardness or a higher density respectively of carbides. This also cannot be counteracted by resource to use some micro tools or respectively Drill bits based on high-value hard metals, for example with a diameter below 0.8 mm. The influence of the carbureted texture components in the region of some strong enrichment also leads in this case to a deviation of the tool from the direction Preset treatment.

Steels of the aforementioned type are known. They have good magnetizability, such as chrome steel soft magnetic described in the patent document of the USA 4,714,502, which has up to 0.03% carbon, from 0.40 to 1.10% silicon, up to 0.50% manganese, 9.0 to 19% chromium, up to 2.5% molybdenum, up to 0.5% nickel, up to 0.5% copper, of 0.02 to 0.25% titanium, 0.010 to 0.030% sulfur, up to 0.03% of nitrogen, 0.31 to 0.60% aluminum, 0.10 to 0.30% lead and from 0.02 to 0.10% zirconium. The steel is stainless and deformable in cold; He is suitable as work material for the production of cores for solenoid valves, electromagnetic clutches, or of housings for electronic injection systems for internal combustion engines.

Other chrome steel, stainless and magnetic soft, which has up to 0.05% carbon, up to 6% silicon, of 11 to 20% chromium, up to 5% aluminum, 0.03 to 0.40% lead, 0.001 to 0.009% calcium and 0.01 to 0.30% tellurium, is known from US Pat. 3,925,063 and, because of its lead, calcium and tellurium content, it has a Good machinability by chip removal.

The relatively high silicon contents, aluminum and titanium lead in the case of this steel, however, because of the formation of hard inclusions of oxides, at a high wear when performing fine mechanical treatment. This is due to oppose the relatively high lead content, from 0.03 to 0.40%. In this case it is disadvantageous, however, the fact that lead it has a very low melting point, and accordingly, it does not form no union or segregation that is stable, and its Texture distribution is extremely heterogeneous.

For the rest, the publication document for German patent application information 101 43 390 A1 describes a ferritic chrome steel, stable against corrosion and cold deformable, having from 0.005% to 0.1% carbon, from 0.2% to 1.2% silicon, 0.4% to 2.0% manganese, 8% to 20% chromium, 0.1% to 1.2% molybdenum, 0.01% to 0.5% nickel, 0.5% to 2.0% copper, from 0.001% to 0.6% bismuth, from 0.002% to 0.1% of vanadium, from 0.002% to 0.1% of titanium, from 0.002% to 0.1% of niobium, of 0.15% to 0.8% sulfur and 0.001% to 0.08% nitrogen, and the rest iron, including impurities caused by fusion, which, due to its good mechanical workability, particularly its good machinability by chip removal, its good resistance to wear and its good surface quality is adapted as a material of work for fine mechanical applications and devices precision, in particular for spinning nozzles and nozzles and injection, as well as writing devices, tips and heads.

The publication document for information on European patent application 1,288,323 A1 further describes a steel to ferritic chromium, stable against corrosion and deformable in cold, which has 8 to 20% chromium, 0.005 to 0.1% carbon, up to 0.08% nitrogen, 0.2 to 1.2% silicon, 0.4 to 2.0% of  manganese, 0.05 to 1.2% molybdenum, 0.01 to 0.50% nickel, 0.5 to 2.0% copper and up to 0.05% lead, selenium and / or tellurium. However, this steel is as arsenic free as a steel ferritic, which is known from the publication document for Japanese patent application information 2001-131.716, which has 15.0 to 25.0% chromium, up to 0.12% carbon, up to 0.05% nitrogen, from 0.05 to 1.00% silicon, 0.50 to 2.50% manganese, 0.01 to 0.50% nickel, from 0.01 to 0.50% copper, 0.02 to 0.25% sulfur and 0.0050 to 0.00400% oxygen, and which, in addition to this, may also contain molybdenum, selenium, lead, bismuth, niobium, vanadium, titanium and Zirconium in proportions not mentioned.

Finally, the patent document of the USA 6,033,625 also describes an exempt ferritic chromium steel  of arsenic, which has 19 to 25% chromium, up to 0.1% carbon, up to 2.0% silicon, up to 2.0% manganese, up to 4.0% of molybdenum, from 0.1 to 4.0% nickel and / or copper, up to 0.4% selenium and from 0.2 to 0.35% sulfur, and the rest iron.

The problem that constitutes the foundation of invention consists in providing a ferritic chromium steel, which Not only is it excellently machinable with chip removal, it is say in particular without the formation of adhesions or of welding inputs, but also can be microtreated in an exact address

The solution to this problem consists of a chrome steel that has

from 14% to 20% of chrome

from 0.005% to 0.05% carbon

up to 0.01% of nitrogen

from 0.2% to 0.6% of silicon

from 0.3% to 1.0% manganese

from 0.1% to 1.0% molybdenum

up to 0.8% of nickel

from 0.2% to 1.0% coppermade

0.02% to 0.2% of selenium

from 0.01% to 0.1% arsenic

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as well as individually or ones next to others

from 0.01% to 0.1% of lead

from 0.01% to 0.5% of bismuth

from 0.01% to 0.1% of antimony

from 0.005% to 0.08% vanadium

from 0.005% to 0.08% titanium

from 0.005% to 0.08% niobium

from 0.005% to 0.08% zirconium

from 0.15% to 0.65% sulfur

up to 0.20% of tellurium,

and the rest, including impurities caused by fusion, iron.

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A chrome steel is particularly suitable that have

from 14% to 18% of chrome

from 0.01% to 0.03% carbon

up to 0.01% of nitrogen

from 0.03% to 0.5% of silicon

from 0.4% to 0.7% manganese

from 0.1% to 0.6% molybdenum

up to 0.5% of nickel

from 0.2% to 0.6% coppermade

from 0.02% to 0.2% of selenium

from 0.01% to 0.05% arsenic

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as well as individually or ones next to others

from 0.01% to 0.05% of lead

from 0.01% to 0.3% of bismuth

from 0.01% to 0.05% of antimony

from 0.005% to 0.08% vanadium

from 0.005% to 0.08% titanium

from 0.005% to 0.08% niobium

from 0.005% to 0.08% zirconium

from 0.15% to 0.65% sulfur

from 0.01% to 0.20% tellurium,

and the rest, including impurities caused by fusion, iron.

In attention to obtain optimal properties of work materials, the composition of steel should satisfy at least one of the following conditions:

one

The simultaneous presence of sulfur, selenium and Tellurium has an especially advantageous effect on properties of work materials, through the presence of fine segregations of sulfides, selenides and tellurides, when the respective contents of these elements satisfy the condition for K3.

For the mechanical properties of steel According to the invention, it is not only about the presence of certain phases of segregation, but also very essentially of its physical quality and its distribution in texture. The texture It contains, therefore, both metal sulphides and also selenides of metals that, in turn, interact with carbides and sulfocarbons, and which, in this case, produce an improvement in chip breaking behavior. In this context, the invention, by the route of transposition and exchange reactions, wants to release certain elements of the alloy in the vicinity of segregations, in order to surround the hard segregations with a lubricating agent zone based on metals and / or metal compounds, which act as zones of lubricating agents and improve the machinability by starting of shavings.

Segregations result only when thermodynamic preconditions allow them. An important indicative magnitude for this is the heat of formation. A negative heat of formation indicates that segregations are Thermodynamically stable. The more negative the heat of training for a certain segregation, the more likely it will be also that it results.

Segregations based on sulfides, selenides or tellurides or mixtures thereof, and also, some segregations, which have to be attributed to some transposition or exchange reactions with carbides, are formed at different temperatures in the solid state of steel. By cooling the melt, results are called primary segregations, that grow during further cooling, become thicker  and give rise to the known disadvantages. Through tuning according to the invention of certain elements, such as lead and / or bismuth and / or arsenic and / or antimony and / or vanadium, titanium, niobium as well as zirconium, with the forming agents of segregations carbon, nitrogen, sulfur, selenium and tellurium, it turns out a large number of reaction possibilities, which repress the harmful growth of primary segregations.

The diagram in Figure 1 shows some training heats for important sulfides and selenides, which are important for the invention. Since all metal compounds have formation heats negative, these are also appropriate to form segregations

In the case of steel according to the invention, the segregation forming agents, which are not metallic - carbon, sulfur, selenium, tellurium and eventually nitrogen - they are present only in a small concentration, in order to avoid oversaturation, since otherwise they form segregations of coarse grains, which grow rapidly. These only with many difficulties could they be reduced in terms of their Grain sizes or dissolve respectively. A low content of carbon appears as especially important, in order to shift the equilibrium of the reaction towards formation of sub-stoichiometric carbides.

Since segregations are formed in a way preferred when cooling, diffusion effects (diffusion of solid bodies in steel) play an important role in the case of the formation and growth of segregations. Fundamentally, elements with a low atomic mass are diffuse easier and faster than heavy atoms. In the steels are therefore very easily formed segregations carbureted and nitride, which are designated as the so-called primary segregations. Only after segregation sulphides and / or selenides or respectively others result segregations such as sulfocarbons and sulfocarboselenides.

Since the carbon content is very small, presumably sub-stoichiometric primary carbides result - that is, with a carbon deficiency. Only after prolonged periods of time, this carbon deficiency is compensated by carbon diffusion or is partially replaced by sulfur or
selenium.

Sub-stoichiometric primary carbides result, for example, corresponding to the equation

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2

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being designated with Me I the elements titanium, vanadium, niobium and zirconium, and x being the factor of stoichiometry. These elements may react, however, also still with nitrogen, sulfur and selenium (tellurium). In this In case sulfocarbons, sulphoselenides or sulfocarboselenides result. Sub-stoichiometric segregations are therefore very reactive also after your training.

The composition of primary carbides (or of primary segregations) of metals Me I may fluctuate within a wide range, without the reticular structure of Segregations suffer for them. So, from the bibliography it is known that, for example, titanium carbide has an especially wide range of stability. This one extends from TiC_ {0.22} to TiC_ {1.0}. For a factor of stoichiometry of, for example, x = 0.5, equation 1 for the titanium would be:

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3

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Because of its position in the periodic system of the elements, sulfur, selenium and also tellurium show similar reactions, which is also visible to from the thermodynamic numerical values in Table I. To the formation of segregations constituted on the basis of sulfur, selenium and tellurium, copper elements are important, lead, arsenic, antimony and manganese; they have to differentiate with respect to the metals Me I and are designated below as the elements Me II.

Typical reaction equations with sulfur and Selenium are:

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4

Y

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5

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The difference with respect to the elements I is that they do not form any carbide, any carbonitride and, as a result, neither sulfocarbon.

The fact is typical for all segregations that so-called areas of impoverishment. These result from the fact that the elements of the matrix, which are necessary for the formation of a segregation, They are extracted by diffusion and incorporated into segregation. In This case results in an evolution of the concentration, as represented in the diagrams of Figures 2 and 3.

Such areas of impoverishment are disadvantageous. for the intended transposition and exchange reactions between segregations, so the invention recommends some special measures, in order to minimize these. Such measures they consist of a combination of a cold deformation and a heat treatment, in which it comes to reactions of transposition and exchange between primary segregations and high schools.

In this case, the resulting segregations new ones dissolve and form, and, for example, can result also copper, which acts as a lubricating agent in the immediate primary segregations. Since the reactions transposition occurs predominantly during the cooling, segregations are necessarily very fine. For Transposition reactions are favorable if available a sufficiently long period of time, since the transport of substances for transposition reactions is done by diffusion. Slow cooling or advantageous are advantageous. a period of downtime at 700 to 500 ° C and / or a final heat treatment

It must be assumed that the reactions of transposition and exchange between Me I segregations sub-stoichiometric carburets and a segregation or multiple Segregations of sulfides and / or selenides are developed by mediating release of certain elements.

An example of a segregation reaction Sub-stoichiometric with a sulfide (in this case copper sulfide) it would be for TiC_ {0,5}:

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6

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Since sulfur from copper sulfide arrives by diffusion to the sulfocarbon reticulum (Ti 4 C 2 S 2), in compensation the copper is released, which results in this case in the immediate proximity of the hard segregation of titanium carbosulfide. When performing start machining of chips, the element released - in this case copper - acts as a lubricating agent Similar reactions also take place. among other segregations of Me I and of sulphides or selenides of Me II (for example, with manganese segregations and lead).

Dissolution reactions according to equation 4 they are very important, since they dissolve or begin to dissolve to Me II sulfides, which are thick or disposed in the form of lines (for example, manganese sulphides) of a advantageous way, forming - corresponding to equation 4 - new microscopic segregations, very fine. Steel chrome according to the invention has, therefore, a texture with many fine segregations (Figure 4).

So that some redisolution reactions or release - corresponding to reaction equations described above - they can take place in a way that fast enough and favorable, the following are advantageous premises:

-

between the different segregations, the routes of diffusion should be small, in order to keep the time periods of reaction;

-

the impoverishment areas in the immediate vicinity of segregations should be degraded, in order to promote the reactivity of segregations;

-

he effect of reaction temperatures and time periods of reaction must be adapted in such a way that the reactions, such as the reaction according to equation 3, take place within a short period of time.

According to the invention, the steel should be First, therefore, subjected to one or more deformations as strong as possible, reaching some displacements by sliding and to an improved intermingling of texture components. Also, in this case, the distances between segregations are also advantageously modified, and the impoverishment zones are degraded A special advantage of the strong deformation is finds in the shortening of the dissemination routes what, by its part, leads to an essential increase in reactivity.

So that the necessary reactions of redisolution and release also take place with a speed enough, steel, which has preferably been deformed into cold, it is counted at 750 to 1,080 ° C (Figure 5). In this region dissolution and release reactions take place mediating formation of new segregations or respectively of some modified segregations in its composition - for example, according to the equation 4 -. In accordance with the invention, in addition, a final annealing at up to 450 ° C, in order to solidify the lubricating agent metals that have been released, or to consolidate the finest segregations that have formed again, harden them in the steel matrix, decompose tensions and adjust the hardness or mechanical strength of the steel. To make the final annealing, at a temperature of> 350ºC can already appear a progressive decrease in hardness, which points to a deconsolidation of the matrix.

Preferably, the steel, after a cold deformation that has been performed at least once, with a degree of deformation of above 65% is counted for 30 up to 60 minutes at 750 to 1,080 ° C and then, in the course of 30 to 180 minutes, mediating a weak contribution of energy, cools in a regulated manner at a temperature of 500 to 700 ° C (Figure 5). In this case, the resulting segregations during the Annealing are stabilized in a diffusion controlled manner. A special advantage is that the steel, during cooling, by a brief and stronger contribution of heat, be maintained at a temperature of, for example, 680 ° C (Figure 5, equation 4).

The invention is illustrated in more detail at then with the help of some examples of realization.

Table I compiles the compositions of the E2 alloy, which falls within the scope of the invention, as well as of comparative alloys E1, E3 to E5 as well as V1 to V8. The Table II reproduces the respective values of K1, K2 and K3 as well as The results of treatment trials. In this case, BV designates a characteristic index for the evolution of the drill, BG designates a characteristic index for the amplitude of degrees and BWG designates a characteristic index for surface quality.

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Example 1

A raw wire with the composition E2, which It has a diameter of 6 mm, after a pickling treatment, It was first subjected to cold deformation in three stages with a total deformation degree of 85% and then annealed for 30 minutes at a temperature of 840 ° C in an atmosphere of a gas protector, as well as then over the course of 120 minutes, it was cooled in a regulated manner to a temperature of 600 ° C. During the cooling an intermediate heating took place performed twice for 15 minutes at a temperature of 760 or respectively 680 ° C without any temperature increase, with in order to achieve a staggered cooling for the stabilization of segregations (compare Figure 5).

Following regulated cooling, the wire cooled in the presence of air without any input additional energy, and, after this, it was calibrated with a degree of 15% deformation. The calibration was followed by a final annealing or respectively a tempering for 15 minutes at 340 ° C. The wire He had excellent workability with micro tools.

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Example 2

A raw wire with the composition E3, which it is not according to the invention, with a diameter of 6 mm, subjected, in turn, to a cold deformation in three stages with a degree of deformation in total of 80%, and then rfecoció during 35 minutes at 900 ° C under a protective gas, as well as, in the course of 160 minutes cooled first, in a regulated manner, from the annealing temperature to a temperature of 620 ° C mediating a low energy input with a constant speed of cooling. This was followed by cooling in the presence of air up to room temperature The wire was then calibrated with a degree of deformation of 20% and was revived (subjected to tempering) for 30 minutes at 280 ° C as well as submitted in the state tempered to a microtreatment of mechanization by starting of chips, with the results recorded in Table II.

In the case of trials, to perform the assessment of machinability by chip removal were carried  Drilling tests are carried out with drill bits of hard metal, which had a diameter of 0.6 mm. In this case

-

be investigated the treatment behavior with the help of the straightness of the drill and was characterized with an index characteristic BV,

-

be rated the amplitude of degrees next to the edge of the drill and expressed with a characteristic BG index as well as

-

be microscopically assessed the smoothness of the drill walls and characterized with a characteristic BWG index.

The rectilinearity of the micro drills is determined from the immersion depth of a spike of steel corresponding to the representation in Figure 6. From the immersion depth E of a test pin, correspondingly to the straight part of the hole, and of the length of the drill, BV was determined as a relative value correspondingly to the relationship

BV = 1 - HE

as a characteristic index for drill evolution. In the case of a drill totally rectilinear, the characteristic index is 0.

Otherwise, the amplitude of degrees BG was measured next to the edge of the drill at an angle of 20 to 30º.

Finally, the microscope was checked machinability by chip removal in the form of extension and the frequency of crumbling and detachment in the inside the drill, as well as in a characteristic index BWG with values from 1 to 4. The BWG value of 1 represents a Defect-free drill while a BWG value of 4 It characterizes strong crumbling. The representation in the Figure 7 illustrates a smooth drill with a BWG value of 1, while that the representation in Figure 8 reproduces a drill with numerous crumbling and a BWG value of 4.

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7

TABLE II

8

Claims (12)

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1. Chrome steel consisting of

from 14% to 20% of chrome

from 0.005% to 0.05% carbon

up to 0.01% of nitrogen

from 0.2% to 0.6% of silicon

from 0.3% to 1.0% manganese

from 0.1% to 1.0% molybdenum

up to 0.8% of nickel

from 0.2% to 1.0% coppermade

0.02% to 0.2% of selenium

from 0.01% to 0.1% arsenic

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as well as individually or ones next to others

from 0.01% to 0.1% of lead

from 0.01% to 0.5% of bismuth

from 0.01% to 0.1% of antimony

from 0.005% to 0.08% vanadium

from 0.005% to 0.08% titanium

from 0.005% to 0.08% niobium

from 0.005% to 0.08% zirconium

from 0.15% to 0.65% sulfur

up to 0.20% of tellurium,

and the rest, including impurities caused by fusion, iron.

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2. Chrome steel according to the claim 1 constituted by

from 14% to 18% of chrome

from 0.01% to 0.03% carbon

up to 0.01% of nitrogen

from 0.3% to 0.5% of silicon

from 0.4% to 0.7% manganese

from 0.1% to 0.6% molybdenum

up to 0.5% of nickel

from 0.2% to 0.6% coppermade

from 0.02% to 0.2% of selenium

from 0.01% to 0.05% arsenic

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as well as individually or ones next to others

from 0.01% to 0.05% of lead

from 0.01% to 0.3% of bismuth

from 0.01% to 0.05% of antimony

from 0.005% to 0.08% vanadium

from 0.005% to 0.08% titanium

from 0.005% to 0.08% niobium

from 0.005% to 0.08% zirconium

from 0.15% to 0.65% sulfur

from 0.01% to 0.20% tellurium,

and the rest, including impurities caused by fusion, iron.

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3. Chrome steel according to claim 1 or 2, characterized by the condition K1 = (% Ti +% V + % Nb +% Zr) / (% C) = from 3 to 12. 4. Chrome steel according to one of claims 1 to 3, characterized by the condition K2 = (% S + 3% Se + 3% Te) / 10 (% C +% N) = 1.5 to 3.5. 5. Chrome steel according to one of claims 1 to 4, characterized by the condition (% S) / (% S + % Se +% Te) = from 0.68 to 0.98. Method for heat treating a cold-deformed steel, which has a composition according to one of claims 1 to 5, characterized in that the steel, after at least one cold deformation with a degree of deformation of total from 65% to 90%, it is counted for 30 to 60 minutes at 750 to 1,080 ° C. 7. Method according to claim 6, characterized in that the steel cools from the annealing temperature in the course of 30 to 180 minutes, mediating a weak energy input, to a temperature of 700 to 500 ° C. 8. Method according to claim 7, characterized in that during cooling the temperature of the steel is kept almost constant at least once for 10 to 30 minutes. 9. Method according to one of claims 6 to 8, characterized in that the steel is finally subjected to heating for at least 450 ° C for at least 30 minutes. 10. Use of an alloy according to one of claims 1 to 9 for the production of about objects intended for treatment with tools shapers 11. Use of an alloy according to one of claims 1 to 9 as work material for some objects, which are produced by micromachining by chip removal. 12. Use of an alloy according to claims 1 to 9 for the production of nozzles for printers, pen lead tips, injection nozzles for chemical and electronic equipment, nozzles and spinning nozzles as well as objects with small dimensions and / or rebates.