US20080181807A1

US20080181807A1 - Material with high ballistic protective effect

Info

Publication number: US20080181807A1
Application number: US11/878,344
Authority: US
Inventors: Horst Saiger
Original assignee: Voestalpine Boehler Bleche GmbH
Current assignee: Voestalpine Boehler Bleche GmbH
Priority date: 2001-12-19
Filing date: 2007-07-24
Publication date: 2008-07-31
Also published as: CA2414305C; US20040031353A1; EP1321535A2; CA2414305A1; ES2238556T3; EP1321535A3; BR0205411A; DE50202536D1; EP1321535B1

Abstract

A process for making an article with ballistic protective effect and an article obtainable thereby, as well as a method of providing an object with ballistic protection provided by a corresponding material. The alloys used for making the article comprise the elements C, Si, Mn, Cr, Ni, Mo and V within certain concentration ranges and contain a limited amount of impurities. This abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser. No. 10/321,451, filed Dec. 18, 2002, which claims priority under 35 U.S.C. § 119 of Austrian Patent Application No. 1991/2001, filed Dec. 19, 2001, and of Austrian Patent Application No. 1992/2001, filed Dec. 19, 2001; the disclosures of the parent U.S. application and the Austrian applications are expressly incorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to the use of known steel alloys as materials for the production of articles with high ballistic protective effect.
2. Discussion of Background Information
The ballistic protective effect of articles, in particular, of those made of two-dimensional material, is generally characterized by their security against a puncture by projectiles and fragments when high-energy weapons act upon them. To an increasing degree there is a demand for a high protective effect and, simultaneously a reduced weight of the article or part and an improved economic efficiency of the production thereof.
According to the recognized opinion of those skilled in the art, the mechanical data obtained from conventional tensile impact and notched impact tests do not allow a direct conclusion with respect to the properties of a material under ballistic stress. Nevertheless, in many cases the values of hardness, impact strength and strength of the material are used as at least a point of reference for predicting the penetration resistance of a protective part. However, ultimately, the “stopped shots” of a sheet metal part characterize its ballistic protective effect.
Assuming by way of approximation that the strength, hardness and toughness of a material do not change with the speed of the stress, it can be predicted that the material of protective parts must have both maximum hardness as well as utmost toughness in order to withstand destruction under ballistic bombardment and to exert a breaking effect on projectiles. For steels and alloys these properties are opposed with respect to their simultaneous maximization so that in terms of stress, in addition to a general improvement of the same, a good balance of toughness and strength of the material is required, in particular upon heat treatment.
Depending upon the desired property profile, carbon steels, low and medium-alloy steels, high-alloy steels and precipitation hardenable alloys with, if necessary, an iron content of less than 55 percent by weight have been proposed for products with ballistic protective effect, and in many cases a composite structure and/or a hard layer on the outer surface of the protective part are recognized as being advantageous.
For example, EP-A-180805, the disclosure of which is expressly incorporated by reference herein in its entirety, discloses a steel helmet made of a low-alloy boron steel, which steel helmet is sandblasted after heat treatment.
An armor plate with a heat-treated microstructure is known from EP-A-1052296, the disclosure of which is expressly incorporated by reference herein in its entirety, which plate has a yield point of >1100 N/mm²as well as a hardness of >400 HB and, with a carbon content in percent by weight of 0.15 to 0.2, essentially comprises 1 to 2 percent by weight chromium (Cr), 0.2 to 0.7 percent by weight molybdenum (Mo), 1.0 to 2.5 percent by weight nickel (Ni), 0.05 to 0.25 percent by weight vanadium (V), the balance being iron (Fe).
From EP-A-580062, the disclosure of which is expressly incorporated by reference herein in its entirety, there is known a process for the manufacture of thick armor plates, in which process the above alloy, with an increased content of carbon and nickel, is first heated in a slab mold to a temperature of above 1150° C., allowed to cool in a forced manner and rolled to the final thickness in the range of 1050 to 900° C., each time with a high forming degree.
A steel armor plate with improved penetration strength against projectiles is described in EP-B-731332, the disclosure of which is expressly incorporated by reference herein in its entirety. The plate has a plurality of inclusions which are oriented essentially parallel to the surface of the plate and are concentrated in a region comprising one quarter to three quarters of the thickness of the plate.
EP-B-247020, the disclosure of which is expressly incorporated by reference herein in its entirety, discloses an armor plate having a base material of tough steel, onto which is applied by cladding at least one hard steel layer that is to face the impact and is comprised of 0.6 to 1.0 percent by weight carbon (C), 0.2 to 2.0 percent by weight silicon (Si), 0.2 to 2.0 percent by weight manganese (Mn), 0.8 to 2.0 percent by weight chromium (Cr), 0.05 to 1.0 percent by weight molybdenum (Mo), 0.05 to 0.35 percent by weight vanadium (V), the balance being iron (Fe) and steel accompanying impurities. In this case, an interlayer of pure nickel or pure iron having a thickness between 0.1 and 15% of the total plate thickness is arranged between the base material and the cladding, which interlayer is connected to the base material and the cladding by roll-bonding. The interlayer not only facilitates the cladding of the base material, but also prevents the cladding material from flaking off, which cladding material, though heat-treatable to a hardness of 55 to 60 HRC, apparently has low toughness as a result.
In addition to the above low and medium alloy steels, high-alloy chromium steel alloys (CH-A-648354) and precipitation-hardened or maraging steels (AT-336659, DE-C-19921961, EP-A-1008659) have also been proposed for ballistic protection as an individual part or in composite structure with a hard outer layer, if necessary. Although these types of steels with a high content of alloying elements of up to 50% can be used advantageously as a material for components with highly effective ballistic protection, they have the disadvantage of being very expensive. The disclosures of the mentioned documents are expressly incorporated by reference herein in their entireties.
In view of the foregoing, it would be desirable to have available materials from which products with high ballistic protective effect and a low weight can be manufactured economically and in a simple manner. These products or parts should have a high bullet or projectile breaking effect, be made of an iron-based alloy, and should have toughness and strength properties that are adjustable by means of heat treatment, with maximization of both properties. Moreover, the material should be suitable for the production of composites and multi-layered parts and should also be capable of being surface hardened and welded.

SUMMARY OF THE INVENTION

The present invention provides a process for making an article with ballistic protective effect. The process comprises the provision of an alloy and the shaping thereof into said article.
According to a first alternative of the process, the alloy comprises, in percent by weight:


	Carbon (C)	0.26 to 0.79;
	Silicon (Si)	0.2 to 1.2;
	Manganese (Mn)	0.2 to 0.9;
	Chromium (Cr)	1.1 to 7.94;
	Molybdenum (Mo)	0.56 to 3.49;
	Vanadium (V)	0.26 to 1.74;

the balance being iron as well as accompanying elements and impurities. In the alloy, the total concentration of phosphorus and sulfur is less than 0.025, the concentration of nickel is less than 0.28, and the total concentration of arsenic, antimony, bismuth, tin, zinc and boron is less than 0.011.

In the present specification and in the appended claims all concentrations are based on the total weight of the composition (e.g., alloy), unless indicated otherwise. Moreover, in the context of concentrations, the term “less than” includes 0% by weight, i.e., complete absence. Also, it should be understood that the numerical values given herein are approximate values, i.e., are not limited to the exact value indicated herein.
In one aspect of the process according to the first alternative, the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight: C 0.36 to 0.64; S±0.36 to 0.9; Mn 0.36 to 0.7; Cr 1.7 to 5.95; Mo 1.05 to 2.9; V 0.36 to 1.25. In another aspect, the alloy comprises one or more (e.g., all) of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight: C 0.41 to 0.58; Si 0.41 to 0.68; Mn 0.41 to 0.59; Cr 2.61 to 5.2; Mo 1.3 to 2.7; V 0.39 to 0.83.
According to a second alternative of the above process, the alloy comprises, in percent by weight:


	Carbon (C)	0.3 to 0.6;
	Silicon (Si)	0.08 to 0.59;
	Manganese (Mn)	0.1 to 0.6;
	Chromium (Cr)	0.9 to 1.5;
	Nickel (Ni)	2.4 to 5.5;

the balance being iron as well as accompanying elements and impurities. In the alloy, the total concentration of phosphorus and sulfur is less than 0.025, the concentration of molybdenum is less than 0.34 and the concentration of tungsten is less than 0.29, the total of the concentration of molybdenum plus half the concentration of tungsten not exceeding 0.38, and the total concentration of arsenic, antimony, bismuth, tin, zinc and boron is less than 0.011.
In one aspect of the process according to the second alternative, the alloy comprises one or more of C, Si, Mn, Cr, and Ni in the following concentrations, in percent by weight: C 0.36 to 0.54; S±0.11 to 0.39; Mn 0.18 to 0.49; Cr 1.15 to 1.4; N±2.56 to 4.9. In another aspect, the alloy comprises one or more (e.g., all) of C, Mn, and Ni in the following concentrations, in percent by weight: C 0.41 to 0.49; Mn 0.25 to 0.38; N±2.9 to 3.9.
In yet another aspect of the process according to the above first and second alternatives, the concentration of sulfur in the alloy is less than 0.005 percent by weight.
In a still further aspect of the process according to the first and second alternatives, the process further comprises subjecting the alloy to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting (optionally under pressure), powder metallurgy or any combination thereof.
In another aspect of the process according to the first and second alternatives, the article is subjected to a heat treatment to a strength of higher than 1800 N/mm², e.g., higher than 2000 N/mm², or even higher than 2100 N/mm².
Furthermore, the present invention also is directed to an article that is obtainable by any of the processes set forth above.
The present invention further provides an article for providing ballistic protection. The article comprises an alloy as set forth above (first and second alternatives), has a strength of higher than 1800 N/mm², e.g., higher than 2000 N/mm²or even higher than 2100 N/mm², and may have been processed as indicated above.
In one aspect, the article has a toughness at room temperature of higher than SEP 150 J, e.g., higher than SEP 185 J, or even higher than SEP 245 J.
In another aspect, the article comprises a plate, e.g., a plate having a thickness of at least 5 mm.
The present invention further provides a method of providing an object (including the human or animal body) with ballistic protection. According to this method, at least one of the surfaces of the object is covered (completely or partially) with a material comprising an alloy selected from those indicated above. The alloy and/or the material may have been processed as set forth above. Furthermore, the material may show the strength and toughness properties indicated for the article provided by the present invention.
The advantages achieved with the invention according to the first alternative as set forth above can essentially be seen in that limiting the content of the impurity elements sulfur and phosphorus to a combined value of less than 0.025 percent by weight results in a high toughness of the material, if, as has been found, at the same time the total concentration of the additional impurity components arsenic, antimony, bismuth, tin, zinc, and boron is kept below 0.011 percent by weight. Because nickel in interaction with the other alloying elements, in particular molybdenum and vanadium, surprisingly increases the danger of a grain-boundary coating, the upper limit of the nickel content is less than 0.28 percent by weight. The advantageous properties achieved by the invention manifest themselves in a firing test by a high proportion of stopped shots, and are particularly apparent in parts that have been heat-treated to a high strength of higher than 1900 N/mm². A still further improvement in the properties of the material is achieved when the sulfur content is kept below 0.005 percent by weight.
Excellent results are achieved in a firing test if one or more of the above elements are present the following concentrations, in percent by weight:


	Carbon (C)	0.36 to 0.64, preferably 0.41 to 0.58;
	Silicon (Si)	0.36 to 0.9, preferably 0.41 to 0.68;
	Manganese (Mn)	0.36 to 0.7, preferably 0.41 to 0.59;
	Chromium (Cr)	1.7 to 5.95, preferably 2.61 to 5.2;
	Molybdenum (Mo)	1.05 to 2.9, preferably 1.3 to 2.7;
	Vanadium (V)	0.36 to 1.25, preferably 0.39 to 0.83.

When present in the above concentrations, the selected elements, in close coordination with the other alloying elements, have a positive effect on the microstructural transformations during heat treatment, i.e., promote an increase in hardness without interfering regions at the grain boundaries, and guarantee the formation of a largely homogeneous heat-treated microstructure during tempering.
It has also been found that in addition to the above-mentioned high purity or low content of impurity elements, respectively, of the material used according to the invention, the manufacturing technology has an effect on the ballistic protective effect of parts made thereof. In other words, the manufacturing technologies ladle metallurgy, vacuum treatment, vacuum smelting or vacuum arc remelting, electroslag remelting (optionally under pressure) and powder metallurgy, individually and in any combination thereof, can have an improving effect on the ballistic protection provided by parts produced in such manner, because the isotropy of the material in particular is promoted thereby. In this regard, a heat treatment can produce higher strength values with improved material toughness, whereby the product is given a substantially increased resistance to puncture by projectiles.
If the material has a strength of higher than 1800 N/mm², preferably higher than 2000 N/mm², in particular above 2100 N/mm², with a toughness at room temperature of higher than SEP 150 J, preferably higher than 185 J, in particular above 245 J, measured in accordance with SEP 1314 (Stahl Eisen Prüfblatt=Steel Iron Testing Standard), the maximum penetration resistance or strength, respectively, can be achieved with low alloying costs of the products.
The advantages achieved with the invention according to the second alternative as set forth above can essentially be seen in that, on the one hand, by selecting the alloying elements and their respective concentrations, a desired high material strength can be achieved by means of a heat treatment. As has been found, a high toughness of the material can, on the other hand, be achieved by means of three additional alloying measures. By limiting the total concentration of sulfur and phosphorus, which elements may interact with respect to a formation of inclusions and embrittlement caused by the coating of grain boundaries, at least the prerequisite for high toughness of the material is provided. The elements molybdenum and tungsten which per se can have a strength increasing effect in alloys, individually and in combination show the tendency to concentrate in an embrittling manner at grain boundaries in the material so that the above-mentioned limitation of the concentrations thereof has a toughness promoting effect. It has also been found that, even in low concentrations, the impurity elements arsenic, antimony, bismuth, tin, zinc, and boron cause a steep drop in the toughness of the material when high mechanical stresses act on the material abruptly, as in the case of, e.g., the bombardment of a part made thereof, which is the reason why the total concentration thereof is limited according to the invention. As also mentioned at the outset, the mechanical properties of a material as determined by means of conventional tests may change substantially when a high-energy weapon acts on the material so that, strictly speaking, the penetration resistance to bullets or fragments as well as the cracking behavior of protective parts can only be evaluated by means of a firing test. The alloy used according to the present invention shows special advantages as a material for products with high ballistic protective effect, not only because of the improved properties associated therewith, but also for economic reasons. In particular, the total concentration of the alloying elements in the alloy is below 8.8 percent by weight, and a low-distortion heat treatment can be performed therewith. The material also shows adequate weldability for component production, e.g., for armor-plating limousines.
Even further improved properties can be achieved in a firing test if one or more of the above elements are present in the following concentrations, in percent by weight:


	Carbon (C)	0.3 to 0.54, preferably 0.41 to 0.49;
	Silicon (Si)	0.11 to 0.39;
	Manganese (Mn)	0.18 to 0.49, preferably 0.25 to 0.38;
	Chromium (Cr)	1.15 to 1.4;
	Nickel (Ni)	2.9 to 4.9, preferably 2.56 to 3.9.

A further improvement in the property profile is obtained by a reducing the sulfur content to below 0.005 percent by weight.
The advantageous properties of the material that are achieved according to the second alternative of the present invention are particularly apparent during a bombardment, if the parts are heat-treated to strength values of above 1900 N/mm². One of the reasons therefor is that a narrower range of the concentration of a respective alloying element which interacts with the other components of the alloy favorably influences the transformation and the development of the microstructure of the material during heat treatment, whereby the increase in hardness and the tempering behavior are improved, resulting in an extensive isotropy with low internal stresses.
The manufacturing technologies ladle metallurgy, vacuum treatment, vacuum smelting or vacuum arc remelting, electroslag remelting (optionally under pressure) and powder metallurgy, individually and in any combination thereof, can have an improving effect on the ballistic protection provided by parts produced in such manner, because the isotropy of the material in particular is promoted thereby, also with regard to microsegregations. In this way, an increase in the toughness of the material can occur in all directions even with heat treatment to higher strengths of the material, and the resistance to puncture by projectiles can be increased.
When the material has a strength of higher than 1800 N/mm², preferably higher than 2000 N/mm², in particular above 2100 N/mm², with a toughness at room temperature of higher than SEP 150 J, preferably higher than 185 J, in particular above 245 J, measured in accordance with SEP 1314 (Stahl Eisen Prüfblatt=Steel Iron Testing Standard), products and protective components, respectively, with a maximum penetration resistance can be produced therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

FIG. 1 shows the percentage of stopped shots as a function of the thickness of a plate made of an alloy used according to the first alternative of the present invention, a maraging steel and a carbon steel, respectively; and

FIG. 2 shows the percentage of stopped shots as a function of the thickness of a plate made of an alloy used according to the second alternative of the present invention, a maraging steel and a carbon steel, respectively.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
The invention according to the first alternative of the present invention will in the following be explained in greater detail with reference to Examples 1 and 2.

EXAMPLE 1

A plate made of an ESU (electroslag remelting) block and having a plate thickness of 6.6 mm and a composition, in percent by weight, of 0.49 carbon (C), 0.59 silicon (Si), 0.3 manganese (Mn), 0.004 sulfur (S), 0.019 phosphorus (P), 3.23 chromium (Cr), 1.37 molybdenum (Mo), 0.29 vanadium (V) as well as 0.19 nickel (Ni), the balance being iron (Fe) and accompanying elements (arsenic, antimony, bismuth, tin, zinc and boron) in a total concentration of 0.008 was heat-treated to a hardness of 56±1 HRC and subjected to a firing test with 100 rounds, of which 93 shots were stopped. A plate made of heat-treated carbon steel was also tested under the same firing conditions, and stopped 57 shots.

EXAMPLE 2

A plate made of Cr—Mo—V steel, treated by ladle metallurgy and vacuum degassed and having a composition, in percent by weight, of 0.45 carbon (C), 0.62 silicon (Si), 0.64 manganese (Mn), 0.016 phosphorus (P), 0.007 sulfur (S), 3.35 chromium (Cr), 1.62 molybdenum (Mo), and 0.32 vanadium (V) was rolled from a slab ingot to a thickness of 7.5 mm. Specimens were fabricated from the plate, heat treated with different technologies and tested. Table 1 shows the heat treatment parameters and the mechanical values obtained.

TABLE 1

	Hardening						Notched impact
Specimen	Temperature	Tempering		Rm	Rp_0.2	A	strength		Hardness
No.	° C.	° C.	Number	N/mm²	N/mm²	%	J	Mean	HRC

A	930	300	1	1941	1441	6.2	167	180	166	171	55
B	930	300	1	1872	1471	7.6	84	209	160	151	53
C	950	300	1	1975	1576	5.6	61	201	171	144	55

The effect of different heat treatment parameters on the mechanical properties of the material is evident from the above results. This clearly suggests an easy adjustment of the desired product properties according to the invention.
About 60% more shots were stopped in the firing test by the plate according to the invention as compared with a plate of heat-treated carbon steel of the same thickness.
In another test, a comparison was made of plates according to the invention with plates made of carbon steel and maraging steel with regard to stopped shots. The indicated values (those plotted in FIG. 1) represent respective mean values of results from at least three shots.
FIG. 1 shows the percentage of stopped shots as a function of the plate thickness. Starting from a sheet thickness of 6 mm upwards, the proportion of shots stopped by a plate produced according to the present invention and a plate produced from a maraging steel is virtually the same under the same bombardment conditions. With regard to economic efficiency, it should be noted that in the material according to the invention, the concentration of alloying elements is about 6%, whereas it is 41.5% in the maraging steel (comparison material), which makes the latter material substantially more expensive than the former.
The invention according to the second alternative of the present invention will be explained in greater detail with reference to Examples 3 and 4.

EXAMPLE 3

A plate having a thickness of 6.8 mm was rolled from a slab ingot made of a vacuum treated steel having a composition, in percent by weight, of 0.5 carbon (C), 0.32 silicon (Si), 0.45 manganese (Mn), 0.017 phosphorus (P), 0.006 sulfur (S), 1.25 chromium (Cr), 0.18 molybdenum (Mo), 0.21 tungsten (W), and 3.97 nickel (Ni), the total concentration of arsenic, antimony, bismuth, tin, and boron being equal to 0.0085.
This rolling stock was tested mechanically after the application of different heat treatment technologies. The results of the corresponding tests are summarized in Table 2.

TABLE 2

	Hardening						Notched impact
Specimen	Temperature	Tempering		Rm	Rp_0.2	A	strength		Hardness
No.	° C.	° C.	Number	N/mm²	N/mm²	%	J	Mean	HRC

AA	840	120	1	2229	1207	6.1	225	245	228	232	55.5
BB	870	120	1	2227	1133	8.6	220	245	218	227	50
CC	840	120	1	2282	1306	5.5	95	233	173	167	57

The firing test showed that the plate with the specimen designation AA had a shot stopping capability of 95; whereas a heat treated-plate made of carbon steel of the same thickness withstood only 56 of 100 bombardments from shots.

EXAMPLE 4

A plate having a thickness of 7.5 mm was manufactured from steel treated by ladle metallurgy and having a composition, in percent by weight, of 0.52 carbon (C), 0.12 silicon (Si), 0.22 manganese (Mn), 0.014 phosphorus (P), 0.003 sulfur (S), 1.42 chromium (Cr), 0.11 molybdenum (Mo), 0.09 tungsten (W), and 0.004 (As+Sb+Bi+Sn+Zn+B). The steel had subsequently been subjected to electroslag remelting. Heat treatment to a hardness of 57 HRC, afforded, at a hardening temperature of 880° C. and with air cooling after tempering at 200° C., a yield point of the material of Rm=2265 N/mm², with an average notched impact strength of 202 J. In the firing test a 68.7% higher number of stopped shots was recorded as compared to a plate made of heat-treated carbon steel under otherwise identical conditions.
In one of the other tests, a comparison was made by means of a firing test with plates according to the present invention and plates made of carbon steel and maraging steel, each heat-treated to the maximum values. FIG. 2 shows the percentage of stopped shots as a function of the plate thickness. Starting at a plate thickness of 5 mm up to a thickness of 10 mm, the shots stopped by the maraging steel and those stopped by the steel according to the invention were proportionally essentially the same, with slight advantages for the material according to the invention in the plate thickness range of above 6 mm.
It can be seen from the above results that the use of a material according to the invention has, one the one hand, a clearly higher ballistic protective effect compared with a material made of carbon steel under the same product form and stress conditions and, on the other hand, has a substantially lower proportion of alloying elements than a maraging steel and, thus, shows economic advantages in the production thereof.
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

Claims

1. A process for making an article with ballistic protective effect, wherein the process comprises providing an alloy which comprises, in percent by weight:

a balance being iron (Fe) as well as accompanying elements and impurities, provided that a total concentration of phosphorus (P) and sulfur (S) is less than 0.025:

P+S<0.025;

a concentration of nickel (Ni) is less than 0.28:

Ni<0.28;

and a total concentration of arsenic (As), antimony (Sb), bismuth (Bi), tin (Sn), zinc (Zn) and boron (B) is less than 0.011:

As+Sb+Bi+Sn+Zn+B<0.011;

and shaping the alloy into said article.

2. The process of claim 1, wherein the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

C 0.36 to 0.64; Si 0.36 to 0.9; Mn 0.36 to 0.7; Cr 1.7 to 5.95; Mo 1.05 to 2.9; V 0.36 to 1.25.

3. The process of claim 1, wherein the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

C 0.41 to 0.58; Si 0.41 to 0.68; Mn 0.41 to 0.59; Cr 2.61 to 5.2; Mo 1.3 to 2.7; V 0.39 to 0.83.

4. The process of claim 2, wherein the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

5. The process of claim 2, wherein a concentration of sulfur in the alloy is less than 0.005 percent by weight.

6. The process of claim 1, which further comprises subjecting the alloy to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting, powder metallurgy or any combination thereof.

7. The process of claim 4, which further comprises subjecting the alloy to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting, powder metallurgy or any combination thereof.

8. The process of claim 1, which further comprises subjecting the article to a heat treatment to a strength of higher than 1800 N/mm².

9. The process of claim 2, which further comprises subjecting the article to a heat treatment to a strength of higher than 2000 N/mm².

10. The process of claim 7, which further comprises subjecting the article to a heat treatment to a strength of higher than 2100 N/mm².

11. The process of claim 1, wherein the alloy comprises C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

C 0.41 to 0.58; Si 0.41 to 0.68; Mn 0.41 to 0.59; Cr 2.61 to 5.2; Mo 1.3 to 2.7; V 0.39 to 0.83;

and wherein the process further comprises subjecting the alloy to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting, powder metallurgy or any combination thereof, and subjecting the article to a heat treatment to a strength of higher than 2000 N/mm².

12. The process of claim 11, wherein the concentration of sulfur in the alloy is less than 0.005 percent by weight.

13. An article obtainable by the process of claim 1.

14. An article obtainable by the process of claim 11.

15. An article for providing ballistic protection, wherein the article comprises an alloy which comprises, in percent by weight:

P+S<0.025;

a concentration of nickel (Ni) is less than 0.28:

Ni<0.28;

As+Sb+Bi+Sn+Zn+B<0.011;

and wherein the article has a strength of higher than 1800 N/mm².

16. The article of claim 15, wherein the article has a toughness at room temperature of higher than SEP 150 J.

17. The article of claim 16, wherein the article has a strength of higher than 2000 N/mm².

18. The article of claim 17, wherein the article has a toughness at room temperature of higher than SEP 185 J.

19. The article of claim 18, wherein the article has a strength of higher than 2100 N/mm².

20. The article of claim 19, wherein the article has a toughness at room temperature of higher than SEP 245 J.

21. The article of claim 16, wherein the article comprises a plate.

22. The article of claim 21, wherein the plate has a thickness of at least 5 mm.

23. The article of claim 17, wherein the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

24. The article of claim 19, wherein the alloy comprises one or more of C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

25. The article of claim 20 in a form of a plate having a thickness of at least 5 mm, wherein the alloy comprises C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

and wherein the alloy has been subjected to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting, powder metallurgy or any combination thereof.

26. A method of providing an object with ballistic protection, comprising covering at least one of the surfaces of the object with a material of an alloy which comprises, in percent by weight:

P+S<0.025;

a concentration of nickel (Ni) is less than 0.28:

Ni<0.28;

As+Sb+Bi+Sn+Zn+B<0.011.

27. The method of claim 26, wherein the alloy comprises C, Si, Mn, Cr, Mo, and V in the following concentrations, in percent by weight:

28. The method of claim 26, wherein the alloy has been subjected to a technology selected from ladle metallurgy, vacuum treatment, vacuum smelting, vacuum arc remelting, electroslag remelting, powder metallurgy or any combination thereof.

29. The method of claim 27, wherein the material has a strength of higher than 1800 N/mm²and a toughness at room temperature of higher than SEP 150 J.

30. The method of claim 29, wherein the material has a strength of higher than 2000 N/mm².

31. The method of claim 30, wherein the material has a toughness at room temperature of higher than SEP 185 J.