DE2209085A1 - Age hardened martensitic nickel steel - Google Patents

Description

Pstssntnnwälta _

DIpl -'.- i.-. ί ·. : AV. * SCHT

D: -. I 5;. r ;. .; ._ Z. 2 Jr.
MQnchon 22, SUsinsdorfstr. <0

81-18.4O3P- February 25, 1972

HITACHI Ltd., Tokyo (Japan)

Age hardened martensitic nickel steel

The invention "relates to an age hardened martensitic nickel steel.

At present, the research activities for developing steels with greatly improved mechanical Strength "accelerated. In the course of this research, a Steel developed which has a matrix structure made up of martensite, the low temperature transformation products of austenite and has great hardness and improved tensile strength when in the martensite state is age hardened. This steel contains nickel as the main alloy component and is used depending on the amount of nickel divided into different groups. It is the 18 wt% nickel type that has the most improved mechanical Has strength and ductility. This nickel

81- (POS 27461) -Tp-r (7)

209837/0861

steel type contains a certain amount of cobalt and molybdenum as alloying elements. The commonly used nickel steel this type contains 7-9 wt .- # cobalt, 3-5 wt .- ^ Molybdenum and 17-19 wt .- ^ nickel. That type of nickel steel however, it has the disadvantage that the cost thereof is the highest among the various types of nickel steels mentioned above because it contains a significant amount of expensive alloying elements.

In view of the above-described disadvantages of the known nickel steel, it has become necessary to use a nickel steel to develop that has as high mechanical strength and ductility as the 18 percent nickel steel type, however, is of low manufacturing cost.

To obtain a nickel steel that can be used to replace the 18 percent nickel steel type, would be to be considered advantageous to improve the properties of the 20 percent or 25 percent nickel steel type. Each of these two types of nickel steel contains a small amount of titanium and aluminum and is precipitated an intermetallic compound Ni ^ (Ti, Al) in a matrix solidified by martensite by means of age hardening treatment. Both types were found to be similar have mechanical properties and are cheaper than the 18 percent nickel steel grade mentioned above. In the meantime are these nickel steels with more nickel than the 18 percent nickel steel grade of this type in terms of mechanical Strength and especially inferior in terms of ductility. The inferiority of the mechanical strength of this Nickel steel types is due to the insufficient strengthening effect due to the aging hardening treatment,

209837/0861

and the inferiority of their ductility is demonstrated by the fact Caused that the Ni ^ (Ti, Al) by age hardening treatment precipitates at the crystallite grain boundaries as well as within the crystallite grains and the precipitates Coarse particles at the crown boundaries increase the brittleness of the steel. In particular, the deteriorates Precipitation at the grain boundaries increases the mechanical strength of the steel due to a notch effect.

Taking this into account, in the known steel alloys of these types, it is found to be advantageous considered adding elements that prevent the crystal grain boundary precipitation of Ni ^ (Ti, Al) and strengthen the steel due to the age hardening treatment to increase the mechanical strength and ductility of the 20 percent or 25 percent nickel steel type.

The invention is therefore based on the object of specifying a new age-hardened martensitic nickel steel, which has such a high mechanical strength and ductility as the nickel steel with 18 wt .- $ nickel, however, it can be produced at low cost, the disadvantageous grain boundary precipitation of Ni, (Ti, Al) being prevented shall be.

The subject of the invention, with which this object is achieved, is an age-hardened martensitic nickel steel, that by weight percent composition 18 to 26 nickel, 0.15-0.35 aluminum, 1-2 titanium, 0.2-4 at least a metal from the group molybdenum, tungsten, vanadium and chromium, up to 0.03 carbon, up to 0.5 manganese,

20983 7/0861

up to 1 niobium, up to 0.1 silicon, up to 0.01 phosphorus, up to 0.01 sulfur, the remainder iron and unavoidable impurities is characterized, wherein the steel has martensite structure and the metal of the group mentioned for Suppressing the precipitation of the intermetallic compound improving the mechanical properties of the steel Ni-z (Al, Ti) is used at the grain boundaries.

The steel according to the invention is age hardenable in the martensitic state and has a high mechanical strength Strength and ductility as great as those of the 18 percent nickel steel grade. The mechanical strength and ductility of the martensitic age hardened nickel steel are practical to the presence of the only in the crystallite grains and not present at the grain boundaries Ni ^ (Ti, Al).

It is largely thanks to the Mo, W, V and / or Cr contents that the steel according to the invention this has as high mechanical strength and ductility as the 18 percent nickel steel grade. And accelerated the existing Mo, W, V and / or Cr the aging hardening and prevents a precipitation of Ni ^ (Ti, Al) at the grain boundaries.

For the most part, the steel is treated by solution heat treatment; H. Heating to the austenitizing temperature for a certain time and then cooled to room temperature in the martensitic state. The lower the the existing nickel content, the easier the transformation into the martensite structure. The steel with 20 wt .- # or less nickel can essentially be completely

2 0 9 S; <7 '0 »6

sit by cooling it to room temperature. % Nickel only by cooling to room temperature not convert completely into martensite, so that partially austenite remains - however, the steel can with more than 20 wt.. These steels with a high nickel content must therefore be subjected to a special treatment to transform them into martensite. A sufficiently satisfactory treatment consists in cooling the steel from the austenitizing temperature to room temperature and the subsequent cooling to a freezing temperature, or preferably at -73 ⁰ C or lower, or it provides to cool the steel to room temperature and it then a Austenitalterungs ( "ausaging" ) treatment at 600-750 ⁰ C for 1 to be subjected to 20 hours "the processing performed age hardening lung after Martensitumwand ™ is prepared by heating to a temperature of 260-590 ⁰ C for 0.1 to 100 hours, or preferably at 450-500 ⁰ C for 0.5-30 hours

When the aforementioned martensite transformation and aging hardening treatments are carried out, the steel has a tensile strength of 165-230 kg / mm and an elongation of 9-13 fo »Compared with the tensile strength of 160-205 kg / mm and the elongation of 8 - 14 ° of the i 18prosentigen Nickelstahltvps currently used can be readily seen that the steel of the invention has characteristics which do not practically be worse than that of the known 18prozentigen nickel steel type. An essential advantage of the steel according to the invention is that it can be produced much more economically because of the lack of a Cobelt-G content.

2 G 9 8? 7/0 3 6

The steel according to the invention contains, as mentioned above, 18-26 wt .- ^ nickel. If the percentage of nickel is below 18 wt .- ^, the curing effect of the Ni -, (Ti, Al) insufficient, and no satisfactory one can be obtained achieve mechanical strength. On the other hand, when the amount of nickel present is greater than 26% by weight, will the transformation into martensite difficult, even if the steel from the austenitizing temperature to room temperature and then it is cooled to the temperature of liquid nitrogen, because the steel is not completely in the martensitic state can convert.

When 20 per cent nickel steel type to be 18 - 22%, in particular 19 - 20 i »nickel and 0.2 to 4 $ Mo, preferable W, V and / or Cr. In the case of the 25 percent nickel steel type, it is preferred to use 23-26 fo, in particular 24-26 nickel and 0.2-3 ^ Mo, W, V and / or Cr.

The precipitation of Ni ^ (Ti, Al) is accelerated depending on the amount of aluminum and titanium. The percentage of aluminum present should be 0.15 to 0.35% by weight and that of titanium 1.0 to 2.0% by weight. If their percentages are greater than the stated values, the hardening effect increases too much and the steel becomes brittle. On the other hand, if their percentages are lower, sufficient hardness cannot be obtained .

As mentioned, Mo, W, V and / or Cr serve to prevent the precipitation of Ni, (Ti, / 1) at the crystallite grain boundaries. At least 0.2 wt. Mo, W, V or Cr is required to be able to expect sufficient effect. Though an excess of Mo, W, V, or Cr for hardening

209837/0861

of the steel contributes, the excessive hardening or solidification by these elements makes the steel in the context of this invention rather brittle, since Ni ^ (Ti, Al) already contributes effectively to the strengthening of the steel. Accordingly, the amount of these elements should be kept in the necessary percentage range in order to prevent the precipitation of Hi., (Ti, Al) at the grain boundaries; In the case of the 20 percent nickel steel type, it is preferable to add 1 to 3 $ Mo, W, V and / or Cr, while in the case of the 25 percent nickel steel type, an addition of 0.5-3% is preferable. The nickel steel according to the invention contains elements whose Percentage is determined essentially on the basis of the above considerations. In addition, the steel according to the invention can contain Nb and / or Mn within the limits specified above.

Niobium has an effect of binding carbon, which is an impurity in steel and deteriorates its ductility, in the form of NbC and thus controlling the undesirable effects of carbon. Accordingly, manganese has an effect of binding sulfur, which is present in the form of impurities in steel and deteriorates its ductility, in the form of MnS. These effects of Nb and Mn can be effectively achieved in the content limits of 16 wt. - / o Nb and 0.5 wt. - ¹ P Mn. Since excessive additions of these elements can easily cause another undesirable effect, their percentage should be kept within the stated limits. A preferable addition amount of Nb is 0.4-0.8 wt. #.

Amounts of sulfur, phosphorus and nitrogen present in steel should be kept as low as possible,

2 0'J'Γ; -.-

as these elements cause undesirable consequences. In addition, carbon and silicon lower the ductility of the Steel and should therefore also be kept as low as possible. As tests have shown, the admissible lies Amount of carbon present in the nickel steel according to the invention up to 0.03 wt. # And the permissible amount by weight of silicon up to 0.1 wt .- ^. What phosphorus and as regards nitrogen, care should be taken to ensure that these elements are each less than 0.01% by weight.

The invention is explained in more detail with reference to the drawing; show in it:

1 and 2 microstructural images of the known 20 percent Mckelsteel type after age hardening s treatment;

3 and 4 microstructural images of the nickel steel according to the invention after the aging hardening treatment;

Fig. 5 is a diagram to explain the tensile strength of 20 percent nickel steel types according to Aging hardening treatment as a function of aging time;

Fig. 6 is a diagram to explain the tensile strength of 25 percent nickel steel types according to Aging hardening treatment as a function of aging time; and

2 U 9 8 'J ■ - "' 0 ^ G

_ 9 -

Pig. 7 shows a 25 percent stress-strain curve Nickel steel types

Examples

The results and effects of the invention have been confirmed by a research program that has a number of measured values using different compositions of the 20 percent nickel steel type and the 25 percent Nickel steel type were obtained as shown in Tables 1 and 2 ο

Table I.

sample σ 0.01 Si Chemical composition (weight-5 Mn Ni Ti Al Nb Mon W. Y Cr Fe No. 0.01 0.02 0.03 0.13 20.8 1.83 0.34 0.38 - - - - Best 1 0.01 0.02 0.04 0.15 19.82 1.81 0.32 0.42 0.21 - - - Il CVJ 0.01 0.01 0.03 0.14 20.13 1.79 0.30 0.39 0.51 - - - Il 3 0.02 0.04 0.14 20.24 1.82 0.31 0.40 1.03 - - - Il 4th 0.02 0.05 0.13 19.75 1.83 0.33 0.41 2.05 - - - Il 5 0.01 0.02 0.14 19.67 1.78 0.29 0.37 3.03 - - - Il 6th 0.02 0.01 0.15 20.21 1.81 0.32 0.43 3.97 - - - Il 7th 0.01 0.02 0.13 21.20 1.85 0.31 0.41 4.52 - - - Il 8th 0.01 0.04 0.13 20.4 1.82 0.35 0.40 - 0.48 - - Il 9 0.02 0.01 0.14 19.8 1.80 0.34 0.41 - 1.07 - - Il 10 11 0.005 0.03 0.15 19.1 1.78 0.33 0.39 - 2.57 - - Il 12th 0.01 0.11 21.3 1.79 0.35 0.42 - 1.47 - - It 13th 0.03 0.12 20.5 1.81 0.26 0.49 - 5.00 - - Il 14th 0.01 0.13 20.3 1.80 0.31 0.38 - - 0.27 - It 15th 0.03 0.11 20.1 1.83 0.30 0.39 - 0.53 Il

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- 10 -Table 2

sample C. Si ( Mn Chemical composition (weight Ti Al Man Mon - V - V Cr Fe Fr. 0.01 0.04 0.14 Ni 1.82 0.54 0.41 - - 2.48 rest 16 0.02 0.03 0.16 20.7 1.80 0.55 0.42 - - 3.02 - It 17th 0.004 0.02 0.15 20.0 1.79 0.56 0.40 - - - 0.25 It 18th 0.01 0.01 0.13 19.5 1.81 0.54 0.57 - - - 0.53 η 19th 0.02 0.02 0.14 19.7 1.80 0.55 0.38 - - - 2.97 η 20th 0.01 0.02 0.13 19.5 1.78 0.52 0.39 0.20 - - 3.49 It 21st 0.02 0.04 0.14 19.8 1.81 0.50 0.42 0.49 - - - η 22nd 0.01 0.05 0.13 25.09 1.82 0.52 0.41 1.05 - - - η 25th 0.02 0.04 0.15 25.55 1.79 0.54 0.40 2.02 - - - It 24 0.05 0.05 0.14 25.91 1.84 0.51 0.38 2.98 - - - η 25th 0.01 0.02 0.16 24.74 1.81 0.50 0.43 - 0.51 - - η 26th 0.01 0.03 0.15 25.56 1.80 0.55 0.42 - 0.89 - - It 27 0.01 0.05 0.13 25.54 1.81 0.51 0.41 - 2.67 - - It 28 0.02 0.02 0.12 24.9 1.82 0.52 0.43 - 4.49 - - η 29 0.007 0.04 0.11 25.2 1.80 0.54 0.40 - 4.97 - - η 50 0.01 0.05 0.14 25.5 1.79 0.55 0.42 - - - - η 51 0.02 0.02 0.15 25.6 1.80 0.52 0.39 - - - - η 52 0.008 0.05 0.14 25.9 1.78 0.50 0.40 - - 0.27 - It 55 0.01 0.04 0.13 24.7 1.76 0.29 0.41 - - 0.54 - H 54 0.009 0.02 0.12 24.8 1.78 0.55 0.42 - - 2.42 - It 55 0.02 0.01 0.16 25.0 1.80 0.54 0.39 - - 3.12 - M. 56 0.01 0.05 0.15 25.1 1.81 0.51 0.42 - - - 0.27 η 57 0.02 0.05 0.17 25.4 1.80 0.50 0.39 - - - 0.59 η 58 0.02 0.02 0.16 24.8 1.79 0.29 0.35 - 2.98 η 59 0.05 0.01 0.13 25.7 1.81 0.54 0.33 - 5.51 η 40 25.5

2098 3 7/0861

The 20 per cent nickel steel type samples according to Table 1 were after one hour of heating to the austenitization temperature of 820 ⁰ C for the purpose of solution heat treatment and cooling to room temperature, the age hardening at a temperature of 450 - 500 ⁰ C subjected. The 25 percent nickel steel type samples according to the table were, after one hour of heating to the austenitizing temperature of 820 ^° C., cooled to room temperature and then subjected to a similar aging treatment after the solution heat treatment and cooling in liquid nitrogen.

Fig. 1 a signal obtained with the electron microscope image showing the microstructure of the sample Nos. 1, which was an age hardening sbehandlung at 450 ⁰ C for 500 minutes after the solution annealing subjected. FIG. 2 shows a microstructure image of sample no. 1, which was subjected to an aging hardening treatment at 450 ^° C. for 2000 minutes.

Both according to Fig. 1 and Fig. 2 one recognizes coarse grains of Ni ^ (Ti, Al), which are precipitated at the crystallite grain boundaries. While Ni, (Ti, Al) precipitates within the crystal grains finely and evenly distributed, one recognizes. hardly any precipitation near the grain boundaries. Steels with such a microstructure are strongly hardened in their crystallite grains, in which fine Ni (Ti, Al) grains are evenly precipitated, but this structure is relatively soft in the vicinity of the crown boundaries, where Ni ₅ (Ti, Al) is due to the Occurrence of obsolescence has not been eliminated. Accordingly, with this nickel steel, when a load is applied, a preferably disruption occurs

209 ^ i 37 /> ')': -:., 1

the grain boundaries, whereby the steel becomes brittle.

3 and 4 show the microstructure of the steel sample No. 5 according to the invention after the age hardening treatment. FIG. 3 shows a structure of the steel that was subjected to an aging treatment at 450 ^° C. for 1000 minutes after the solution heat treatment. FIG. 4 also shows a structure of the same steel which, however, was subjected to an aging hardening treatment at 450 ^° C. for 500 minutes after the solution heat treatment »

No excretion is observed in Figures 3 and 4

at the grain boundaries «. Ni, (Ti, Al) is fine and uniform

both in the crystallite grains and in the neighborhood the grain boundaries distributed.

The nickel steel with the structure described above has a high resistance to loads and excellent ductility. The tensile strength and elongation of the nickel steels listed in Tables 1 and 2, as they are after the solution heat treatment or after the age hardening treatment are given in Tables 3 and 4.

20 9 H: - ■ η χ η

Table 3

Solution annealed Deh
tion
(*) 450 ⁰ C
χ 3 h Aging 475 ⁰ C
χ 3 h Aging 500
χ 3 ⁰ C
H Aging ^No. train
firm
speed
(kg / mnO Z.,
(kg / mm * , D.
■) GO Z. j
(kg / mm ⁴ , D.
·) (*) Z
(kg / mm D.
) (*)

10
11
12th
13th
14th
15th
16

90.0

91.3 91.2 92.1 93.5

103.2 99.0

101.3 90.7 91.3 92.1 93.5 95.7 92.3 90.7 91.5 92.3 91.0 90.7 92.3 91.7

12.7 12.5 11.9 12.3

10.9 11.7

12.5 11.9 12.5 12.0

11.7 10.9 12.5 12.0

11.7

12.0 10.9 10.9 11.0 12.0 11.7

140.5 166.3 173.5 174.0 178.9 200.3 198.0 195.2 169.7 170.9 173.0

175.7 170.6

155.7 178.5 178.5 170.7 150.7 185.1

184.1 147.9

3.4
10.3

9.6 11.0

10.7
9.8

9.4
6.2
7.8

10.7
11.0

10.9
5.7 4.3 8.0

8.5
4.2

4.7 9.5 9.7 4.3

137.5 170.5 178.2

180.3

183.5 195.5 201.8

197.9 170.8

175.9 180.7 181.3 178.0

157.9

180.4 182.5 171.7 152.7 191.3 192.7 157.7

4.7

11.3

11.3

12.5

10.7

11.5

9.8

6.3

6.3

10.5

10.4

10.1

4.3 3.7 8.2 8.0
5.2
3.7
9.0
8.9
5.1

43.7 175.9

188.7 196.5 193.5 197.4 205.0 195.8 175.3 181.3 182.4 185.3 180.4 160.7 184.7 183.5 170.5 155.7 193.2 194.7 160.7

2.9 11.9 10.9 11.5 10.7 11.0

9.7

6.5

4.3

11.4

10.7

10.5

7.5

4.7

7.5

3.1

4.3

4.7

9.0

9.7 7.8

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Table 4 LöBungBannealed 45O ° C aging 475 ° C aging 50O ⁰ C aging

x 5

χ 5

x 3

Train- Ben- Z. 2.5 Z. S. Z. S. ) 4.9 (kg / mm ² ) (» 10.4 9 22nd 101.7 11.7 150.9 11.5 155.7 5.7 140.7 9 23 100.2 12.5 195.5 12.4 24 102.5 15.0 204.7 10.7 25th 105.5 11.0 212.8 11.4 26th 105.7 12.5 222.5 4.7 2.9 27 109.9 11.8 250.1 11.7 11.3 28 100.2 12.5 170.7 10.9 169.7 5.3 170.7 10.7 29 102.4 10.7 190.8 10.7 195.2 10.7 197.7 10.0 30th 104.7 11.7 195.9 4.7 199.7 11.0 201.7 6.4 31 105.7 11.6 199.7 5.7 202.7 10.7 2o5.7 4.7 52 1o6.7 11.9 175.7 9.0 170.7 5.2 171.7 10.1 55 1o7.8 10.9 157.7 9.5 160.7 2.9 159.7 10.3 54 1o6.5 11.5 185.7 4.7 189.7 10.5 191.7 4.5 55 105.4 12.1 189.7 4.5 190.5 10.3 195.7 4.3 56 104.7 10.9 170.7 9.7 165.7 3.7 157.5 9.0 57 105.7 11.7 160.5 9.5 165.7 5.7 160.7 9.5 58 1o1.7 11.8 185.7 4.7 187.9 9.5 190.1 4.7 59 102.6 12.0 185.7 188.5 9.7 191.7 40 102.5 12.5 147.5 140.7 5.7 147.5

2098 3 7/0861

If one uses the known 20 percent nickel steel type No. 1 with the 20 percent Hiek steel types according to the invention and the known 25 percent nickel steel type No. 22 with the 25 percent nickel steel types according to FIG Invention compares, one finds the tensile strength and elongation in both cases about the same, if the steels only are solution annealed. However, after they are age hardened, there is a big difference between them. and although the nickel steel without Mo content becomes the nickel steel with Mo content in terms of both tensile strength and Very inferior to elongation.

Thus, the presence of Mo, W, V and Cr in such a nickel steel increases both strength and strength Ductility, which of course is based on the delayed or prevented precipitation of Ni (Ti, Al) at the grain boundaries.

In the case of a nickel steel according to the invention, the tensile strength increases when the content of Mo, W, Y and Cr increases and does not exceed 4% by weight. When Mo is added, the elongation percentage is not varied as much or is substantially constant in the range of 0.21-3.03 wt%. However, if the content exceeds 4% by weight of Mo, Mo leads to a decrease in tensile strength and elongation after the aging hardening treatment, particularly a large decrease in elongation, as shown in Example No. 8.

It is a surprising and unexpected fact that the elongation is more than twice that of the known Steel is and that the mechanical strength can also be greatly increased by only 0.2-4 wt .- $ Mo, W, V and / or Cr added to the known 20 percent or 25 percent nickel steel type.

Pig. 5, the tensile strength of the steels 1 shows the 20 per cent nickel type no. - No. 7, which were processed by means of solution heat aging at 450 ⁰ C, and the values are plotted as a puncture of the aging time.. The tensile break test was carried out on 4 specimens from a single sample and the results were plotted as they actually spread to show the range of variation.

Samples 2-7 of the steel according to the invention show a tendency to increase the tensile strength with elongation the aging time and have only a small deviation in the measured values. On the other hand, sample No. 1 is not only in terms of inferior to the tensile strength, but also shows a wider range of scatter of the measured values. Next posed It is found in the sample No. 1 of the known steel that the tensile strength decreases when the aging time is 100 minutes exceeds. This probably means that the steel becomes brittle as it ages, and accordingly it goes without saying that that this known type of steel is suitable for a large-sized object requiring a long aging time, is unsuitable.

Fig. 6 shows the tensile strength of the steels Nos. 22 - 27, 25 percent of the nickel type that have been processed after the solution by means of aging treatment at 450 ⁰ C, and the values are plotted as a re-puncture of the aging time. Here, too, one recognizes the same tendency as in FIG. 5 and the superiority of the nickel steels according to the invention.

Fig. 7 shows load-elongation curves, which the loading

2 U ¹ JH 3 i I U 8 B 1

load-elongation behavior of the steel sample Ur. 22 of the "known 25 percent nickel steel type which was subjected to heating for aging at 450 ^° C. for 2 hours after the solution heat treatment, and the steel sample No. 26 of the 25 percent nickel steel type according to the invention. According to the results shown in this graph, the sample No. 22 was broken. 22 of the known nickel steel in the course of elastic elongation under load of about 140 kg / mm or less, and the occurrence of embrittlement was recognized, while sample No. 26 of the steel according to the invention showed plastic elongation when the load reached its elasticity.

reached the limit of 220 kg / mm, and no embrittlement occurred.

As the above description of some exemplary embodiments of the invention shows, the inventive Steel has a higher ductility than that of the known 20 percent or 25 percent nickel steel type. Besides, lets According to the invention, the mechanical strength also improves to a large extent. In addition, there is the nod aiii according to the invention does not contain cobalt, which is an expensive Element is a great advantage of the invention in practical terms that the steel in comparison with the well-known 18 percent Nicke! steel type is cheaper.

209337 / ^ 381

Claims (9)

Claims 1. Age hardened martensitic nickel steel, characterized by the weight percent composition 18-26 nickel, 0.15-0.35 aluminum, 1 - 2 titanium, 0.2-4 at least one metal from the group molybdenum, tungsten, vanadium and chromium, up to 0.03 carbon, up to 0.5 manganese, up to 1 niobium, up to 0.1 silicon, up to 0.01 phosphorus, up to 0.01 sulfur, remainder Iron and unavoidable impurities, the steel having a martensite structure and the metal belonging to the group mentioned to suppress the precipitation of the intermetallics which improve the mechanical properties of the steel Compound Ni ^ (Al, Ti) is used at the grain boundaries. 2. Nickel steel according to claim 1, characterized in that it contains 23-26 nickel and 0.2-3 molybdenum, tungsten, Contains vanadium and / or chromium. 3 nickel steel according to claim 1, characterized in that that it contains 19-21 nickel and 1-3 molybdenum, tungsten, vanadium and / or chromium. 4. Nickel steel according to claim 1, characterized in that it contains 24-26 nickel, 0.5-3 molybdenum, tungsten, vanadium and / or chromium, up to 0.05 silicon, 0.1-0.2 manganese and 0.4-0.8 niobium. 5. Nickel steel according to claim 1, characterized in that 20983 7 / 08G! that it contains 0.2-4 only one of the metals molybdenum, tungsten or vanadium and 0.4-0.8 niobium. 6. Nickel steel according to claim 1, characterized in that it contains 0.2-4 chromium and no niobium. 7. A method for the heat treatment of a nickel steel according to claim 1 with essentially in percent by weight 18-22 nickel, 0.15-0.35 aluminum, 1-2 titanium, 0.2-4 at least one metal from the group molybdenum, tungsten, vanadium and Chromium, up to 0.03 carbon, up to 0.5 manganese, up to 1 niobium, up to 0.1 silicon, up to 0.01 phosphorus, up to 0.01 sulfur, the remainder essentially iron, characterized in that the steel is subjected to a solution heat treatment under the condition of sufficient austenitization of the steel, the steel is cooled to room temperature or about room temperature for the purpose of converting the austenite structure into martensite structure and an aging hardening treatment of this steel at a temperature of 400-550 ^° C. for 0.5-30 Hours during which an intermetallic compound Ni, (Al, Ti) is precipitated essentially only in the crystallite grains. 8. A method for the heat treatment of a nickel steel consisting essentially in percent by weight of 23 - 26 nickel, 0.15 - 0.35 aluminum, 1 - 2 titanium, 0.2 - 3 of at least one metal from the group molybdenum, tungsten, vanadium and chromium, up to 1 niobium, up to 0.03 carbon, up to 0.5 manganese, up to 0.1 silicon, up to 0.01 phosphorus, up to 0.01 Sulfur, the remainder essentially iron, characterized in that the steel is subjected to a solution heat treatment 3 7 / O Η 6 1 subjecting the condition of a sufficient austenitization of the steel, the steel is cooled to a temperature of -73 ⁰ C or lower in order to transform the austenite into martensite, and a age hardening this steel at a temperature of 400-550 ⁰ C for 0.5 - 30 hours performs , in which an intermetallic compound Ni, (Al, Ti) is essentially only precipitated in the crystallite grains. 9. Modification of the method according to claim 8, characterized in that the Umw ⁰ " ¹ 'development of the austenite structure in the martensite structure instead of üby cooling to -73 ⁰ C or lower by cooling to room temperature or about room temperature and by austenite aging (" ausaging " takes place 750 ⁰ C for 1 to 20 hours, - treatment at a temperature of 600th 209837/0861