RU2415368C1 - Procedure for production of steel sheets for heterogeneous armour protecting structures - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel sheets for heterogeneous armour protecting structures with front and back sheets are produced by hot rolling steel work pieces and quenching sheets to martensite with following tempering. Also, work pieces are produced out of steel containing the following chemical composition, wt %: 0.15-0.60 C; 0.10-1.20 Si; 0.15-0.70 Mn; 0.30-1.40 Cr; 0.60-1.90 Ni; 0.10-0.50 Mo; not more 0.15 V; not more 0.35 Cu; not more 0.012 S; not more 0.01 and P; the rest - Fe. Concentration of carbon in steel for front and back sheets is within ranges 0.30-0.60 and 0.15-0.35 wt % correspondingly. Upon rolling sheets are immediately quenched starting from temperature of end of rolling not over 750 and 850°C for front and back sheets correspondingly. Sheets are tempered at temperature not above 180°C and conditioned for not over 8 h and 230°C with conditioning not over 6 h for front and back sheets correspondingly. Front and back sheets are rolled to thickness corresponding to about 0.3 and 0.5 shares of calibre diametre of an armour-piercing bullet with high-strength core designated correspondingly B200F and B200T.

EFFECT: raised battle properties of heterogeneous armour protecting structures and their reduced weight.

1 cl, 3 tbl

Description

The invention relates to the field of metallurgy, specifically to the production of steel sheets of armored protection, in particular for personal protective equipment (body armor, shields, etc.), lightly armored combat vehicles, aircraft, armored structures and building armored structures.

A known method for the production of sheet heterogeneous armor, including obtaining sheets of steel of the following composition, wt.%:

Carbon 0.20-0.27 Silicon 1.20-1.50 Manganese 0.30-0.90 Chromium 1.10-1.50 Nickel 0.50-1.20 Molybdenum 0.15-0.35 Iron Rest.

The front side of the sheet steel is subjected to chemical-thermal treatment (cementation) to a depth of 20-40% of the thickness of the armor, after which it is heated at a speed of 1.2-2.5 ° C / s to a temperature of 920-950 ° C, maintained at this temperature 15 min, quenched and released at a temperature of 110-150 ° C [1].

The disadvantages of this method are that in the process of chemical-thermal treatment, the distribution of carbon over the thickness and area of the sheet is uneven and does not lend itself to leveling. This reduces the uniformity of hardening, the armor-protective effectiveness of heterogeneous armor, and for its guaranteed use, an increase in the thickness of the sheets and the mass of the armor-resistant structure is required.

In addition, this method is not suitable for the production of steel sheets for heterogeneous armored structures against weapons of increased caliber, for example, in military vehicles, because during chemical-thermal treatment, the insufficient surface layer of the steel sheet is hardened.

The closest analogue to the present invention is a method for the production of heterogeneous steel armor in the form of two steel sheets (front and rear components) obtained by hot rolling. The front and rear components are made of steels with different concentrations of carbon.

The steel of which the front component is made has the following chemical composition, wt.%:

Carbon 0.30-0.80 Manganese 0.40-1.20 Silicon 0.10-0.80 Chromium 0.20-2.80 Molybdenum 0.05-1.00 Aluminum 0.01-0.05 Nickel up to 0.440 Phosphorus up to 0.015 Sulfur up to 0.015 Iron Rest.

The back component has the following chemical composition, wt.%:

Carbon 0.17-0.40 Manganese 0.40-2.00 Silicon 0.10-0.80 Chromium 0.10-1.50 Molybdenum 0.05-1.50 Aluminum 0.01-0.05 Phosphorus up to 0.025 Sulfur up to 0.025 Iron Rest.

This method includes hot rolling of steel sheets, heating to a temperature of 880-980 ° C, aging, quenching on martensite and low-temperature tempering at a temperature of 170-230 ° C [2].

The disadvantages of this method are that the heterogeneous armor has poor armor properties relative to the defeat of the latest generation of armor-piercing bullets, especially the improved 7.62 mm caliber cartridge (index 7H23) with a modernized bullet with a new high-hardness hardened core made of U12A tool steel with increased penetration of hard armor barriers. Improving the armor properties by increasing the thickness of the sheets for the front and rear components leads to an unacceptable increase in the mass of armored structures.

The technical problem solved by the invention is to increase the armor properties of heterogeneous armored structures and reduce their mass.

The specified technical problem is solved by the fact that in the known method for the production of steel sheets for heterogeneous armored structures containing front and rear components made of steels with different carbon concentrations, including hot rolling of steel billets and hardening of sheets on martensite with subsequent tempering, according to the invention, a billet for the front sheet is made of steel containing the following chemical composition, wt.%:

Carbon 0.3-0.6 Silicon 0.10-1.20 Manganese 0.15-0.70 Chromium 0.30-1.40 Nickel 0.60-1.90 Molybdenum 0.10-0.50 vanadium no more than 0,15 copper no more than 0,35 sulfur no more than 0,012 phosphorus no more than 0,010 iron rest,

and for the back sheet - from steel containing the following chemical composition, wt.%:

carbon 0.15-0.35 belt 0.10-1.20 manganese 0.15-0.70 chromium 0.30-1.40 nickel 0.60-1.90 molybdenum 0.10-0.50, vanadium no more 0.15 copper no more 0.35 sulfur no more 0.012 phosphorus no more 0.010 iron rest,

hardening of the front and back sheets is carried out immediately from the temperature of the end of rolling, which is not higher than 750 and 850 ° C, respectively, tempering of the front sheet is carried out at temperatures not higher than 180 ° C with a shutter speed of not more than 8 hours, and the back sheet is not higher than 230 ° C a shutter speed of not more than 6 hours. Steel front and back sheets are subjected to hot rolling to a thickness of approximately 0.3 and 0.5 parts of the caliber diameter of armor-piercing bullets, respectively.

The invention consists in the following. To increase the armor properties and reduce the mass of a heterogeneous armor-resistant structure, it is necessary to provide an optimal combination of different mechanical properties and thicknesses of the interconnected front and rear components, taking into account the caliber of armor-piercing bullets equipped with a high-hard heat-strengthened steel core. The front component should functionally have a higher hardness (59-62 HRC) for fragmented destruction of such a core. Destroying in collision with a bullet, the frontal component must maintain the integrity of the rear component, the armor structure as a whole and the protected object intact. The rear component must functionally absorb the energy of the destruction fragments of the bullet and the front component. This is achieved due to the increased viscosity properties (KCU≥0.6 MJ / m ² ) and, as a result, somewhat reduced hardness (55-57 HRC).

The indicated heterogeneous combination of mechanical and functional properties is ensured by using steel of the proposed composition due to differentiation of carbon concentration in the front and rear components, due to which, as a result of immediate quenching and subsequent tempering, maximum armor properties are formed for a heterogeneous structure that successfully resists modern bullets of the prevailing type 7N23 caliber 7. 62 mm.

The highest armor properties, provided that the minimum weight of the armor, depending on the required booking class, is achieved with interconnected thicknesses of the front and rear components, respectively, of about 0.3 and 0.5 parts of the caliber diameter of armor-piercing bullets in the range of shooting systems of calibers from 5.45 mm up up to 14.5 mm.

Carbon reinforces hardened steel. When the carbon concentration in the back component is less than 0.15%, the required strength and hardness are not achieved, and when its concentration is more than 0.35%, the viscosity, ductility and armor protection properties of hardened low tempered steel are reduced. An increase in carbon concentration of more than 0.60% in the frontal component leads to cracking upon impact by 7H23 bullets. At the same time, a decrease in the carbon content in the front component of less than 0.30% does not provide fragmented core destruction, which requires an increase in the thickness of the heterogeneous steel sheets of both components and the mass of the heterogeneous structure.

Silicon deoxidizes steel, increases strength and elasticity in a hardened and low tempered state. But the main thing is that it hardens steel without the formation of inclusions of carbides and nitrides, increases the resistance of martensite to tempering when it hits a bullet. At a silicon concentration of less than 0.10%, the strength and hardness of steel components are lower than permissible, and at a concentration of more than 1.20%, ductility and viscosity are reduced, which does not ensure the achievement of maximum armor properties.

Manganese deoxidizes and hardens steel. When its concentration is less than 0.15%, the hardness and strength of the front and rear components decreases. An increase in manganese concentration of more than 0.7% in combination with chromium leads to the appearance of cracks during bullet strikes, which reduces the armor properties of the heterogeneous structure as a whole.

Chrome increases the strength, toughness and armor resistance of steel. At a concentration of less than 0.30%, the strength and viscosity of both components are below acceptable values. An increase in chromium content of more than 1.40% leads to a loss of ductility and armor resistance due to an increase in internal stresses in hardened low tempered steel.

Nickel helps increase the ductility and toughness of hardened low tempered steel. However, when its content is more than 1.90%, the content of residual austenite in steel increases and its armor properties deteriorate. A decrease in the nickel content of less than 0.60% leads to a loss of ductility and toughness during bullet impacts.

Molybdenum and vanadium favorably change the distribution of harmful impurities in martensite, reducing their concentration along grain boundaries, increase the strength and toughness of steel, and determine the fine-grained microstructure. When the molybdenum content is less than 0.1%, the strength properties of steel are lower than the required level. An increase in the molybdenum content of more than 0.50%, as well as vanadium of more than 0.15%, worsens the ductility and armor properties of hardened low tempered steel. In both cases, the maximum possible armor properties of heterogeneous structures are not achieved.

Copper increases the stability of the martensitic structure in collisions with bullets. However, an increase in copper concentration of more than 0.35% reduces the toughness, as a result, the maximum possible armor properties of heterogeneous structures are not achieved.

Sulfur and phosphorus in this steel are harmful impurities, their concentration should be as low as possible. However, when sulfur concentration is not more than 0.012% and phosphorus is not more than 0.010%, their negative effect on the properties of steel is negligible. At the same time, deeper desulfurization and dephosphorization of steel significantly increase the cost of its production, which is impractical.

Tests of samples of heterogeneous armor-protective structures made of sheets of steel with the proposed composition fired by bullets with a high-strength core according to the standard method showed that the highest conditional armor properties with a minimum mass take place with a thickness of the front and rear components of about 0.3 and 0.5 fractions of a caliber diameter used bullets. Reducing thicknesses of less than 0.3 and 0.5 caliber diameter of bullets increases the likelihood of minor and permissible damage, and their increase of more than 0.3 and 0.5 caliber diameter of bullets leads to an unjustified increase in the mass of armored structures.

The highest functional properties of heterogeneous armored structures were obtained in the case of immediate hardening of steel sheets from the temperature of the end of rolling. However, at temperatures of the end of rolling above 750 ° C and 850 ° C for front and rear components, respectively, martensite lost the microstructural advantages of batch rack morphology, respectively, the hardness, strength and toughness of steel decreased, its armor properties worsened, it was necessary to increase the thickness of sheets and the weight of armor-resistant structures .

At a tempering temperature of the front components above 180 ° C and a holding time of more than 8 hours, as well as a tempering temperature of the rear components above 230 ° C and a holding time of more than 6 hours, their hardness, strength and armor properties drop. Therefore, to eliminate the likelihood of damage to heterogeneous armored structures, an increase in the thickness of steel sheets was required, which leads to an increase in the mass of armored structures.

Method implementation examples

In smelting and refining units, steel is smelted for heterogeneous armored structures: frontal and rear components (Table 1). Smelted steel is poured into ingots, which are rolled into flat blanks with a thickness of 80 mm. The compositions of sheet steels produced by the claimed method for the front and rear components of an armored heterogeneous structure are designated respectively B200F and B200T.

Flat blanks for front components made of steel of composition 3 (Table 1) are subjected to abrasive cleaning, heated to austenitizing temperature T _af = 1250 ° C, and then rolled on a sheet reversing mill 2000 with a temperature of rolling end T _KPF = 660 ° C into sheets for frontal components of the final thickness H _f = 2.3 mm, which is about H _f = 0.3 · d of gauge diameter d of armor-piercing bullets with a high-strength core of caliber d = 7.62 mm.

Table 1 The chemical composition of steels for front and rear components Composition number The content of chemical elements, wt.% FROM Si Mn Cr Ni Mo V Cu S R Fe Front component B200F one 0.29 0.09 0.14 0.29 0.50 0.09 0.05 0.20 0.010 0.007 The basis 2 0.30 0.10 0.15 0.30 0.60 0.10 0.06 0.20 0.010 0.008 -: - 3 0.45 0.40 0.42 0.85 1.20 0.30 0.10 0.32 0.011 0.009 -: - four 0.60 1.20 0.70 1.40 1.90 0.50 0.15 0.35 0.012 0.010 -: - 5 0.68 1.30 0.80 1,50 1.98 0.52 0.16 0.36 0.013 0.011 -: - Rear component B200T 6 0.14 0.09 0.14 0.29 0.50 0.09 0.05 0.18 0.011 0.006 The basis 7 0.15 0.10 0.15 0.30 0.60 0.10 0.06 0.20 0.012 0.005 -: - 8 0.25 0.52 0.50 0.81 1.30 0.38 0.11 0.30 0.011 0.008 -: - 9 0.35 1.20 0.70 1.40 1.90 0.50 0.15 0.35 0.012 0.010 -: - 10 0.36 1.22 0.75 1.43 1.93 0.51 0.16 0.37 0.014 0.012 -: -

The rolled sheets are subjected to immediate quenching with water, and then released at a temperature of _of = 160 ° C with an exposure time _{of of of} 7 hours.

Flat blanks for steel rear components with composition 8 (Table 1) are subjected to abrasive cleaning, heated to austenitizing temperature T _at = 1200 ° C, and then rolled on a sheet reversing mill 2000 with a temperature of rolling end T _cpt = 760 ° C into sheets for the rear components of the final thickness H _t = 3.8 mm, which is about 0.5 · d gauge diameter d = 7.62 mm armor-piercing bullet with a high-strength core.

The rolled sheets at a temperature of T _cpt = 760 ° C are subjected to immediate quenching with water, and then released at a temperature of T _from = 160 ° C with an exposure time of τ _from = 5 hours

Options for the implementation of steel sheet production modes for front and rear components are presented in Table 2.

table 2 Sheet production modes for front and rear components Option No. Composition number N _f (N _t ) T _KPF (T _KPT ), ° С T _of (T _from ), ° C τ _of (τ _from ), h Front component B200F one 5 0.2 d 960 190 3 2 2 0.3 d 750 180 four 3 3 0.3 d 725 160 5 four four 0.3 d 750 150 6 5 one 0.4d 640 140 7 Rear component B200T 6 10 0.4d 730 150 8 7 6 0.5 d 750 155 6 8 7 0.5 d 760 160 5 9 8 0.5 d 850 230 four 10 9 0.6 d 880 240 3

Sheets for the front and rear components are subjected to mechanical tests. The test results of the mechanical properties of the components are given in table.3. The data presented in table 3 indicate that when implementing the proposed method, the highest complex of mechanical properties of the sheets is achieved both for the front (options 2-4) and for the back (options 7-9) components. In cases of transcendental values of the declared parameters, there is a deterioration in the mechanical properties of the sheets for both the front (options 1 and 5) and the rear (options 6 and 10) components.

Table 3 Mechanical properties of steel sheets for front and rear components of heterogeneous armored structures Option No. HRC, units σ _B , MPa σ _t , MPa δ ₄ ,% KCU, MJ / m ² Front component B200F one. 57 1680 1430 5 0.2 2. 59 1800 1500 7 0.5 3. 62 1900 1600 8 0.5 four. 61 1850 1520 7 0.5 5. 55 1650 1400 5 0.3 Rear component B200T 6. 53 1690 1350 7 0.5 7. 56 1700 1400 8 0.6 8. 57 1750 1450 9 0.7 9. 55 1700 1400 8 0.7 10. 52 1680 1300 7 0.5

The resulting sheets with dimensions of 300 × 300 mm were connected inseparably pairwise frontal and rear for testing heterogeneous armor-resistant structures, after which they were full-scale bench-mounted bulletproof tests by firing bullet-piercing bullets of 7H23 index caliber 7.62 mm rounds from a Kalashnikov assault rifle. The shelling was conducted normal to the frontal and, respectively, rear components of the heterogeneous structure.

Bulletproof tests showed that when using steel sheets as the front components produced according to the proposed modes (options 2-4) in one-piece connection with the rear components (options 7-9), non-penetration of heterogeneous armor structures is ensured when the 7H23 cartridge bullets are hit in them . When using steel sheets as the front components manufactured according to options 1 and 5 in pairs with rear components manufactured according to options 6 and 10, unacceptable breakdowns of flat heterogeneous structures by 7N23 bullets took place.

The prototype method is adopted as a base object for comparison. When comparing it was found that with the same total thickness of the heterogeneous armor as when using components from the declared steel, the known method does not ensure its penetration by armor-piercing bullets of cartridges 7N23. To ensure offset non-penetration, it is necessary to increase the thickness of the armor obtained by the known method, not less than 1.3 times. The consequence of this is an unacceptable increase in the mass of a heterogeneous armored structure.

Sources used in the preparation of the description of the invention:

1. Patent of the Russian Federation No. 2090828, IPC F41H 5/04, C21D 9/46, C23C 8/22, 1997.

2. US patent No. 4645720, IPC F41H 5/04, 1987 - prototype.

Claims (2)

1. A method of manufacturing steel sheets for a heterogeneous armor-resistant structure with front and back sheets made of steel with various carbon concentrations, including hot rolling of steel billets and hardening of the sheets on martensite with subsequent tempering, characterized in that the billet for the front sheet is obtained from steel of the following chemical composition, wt.%:
carbon 0.30-0.60 silicon 0.10-1.20 manganese 0.15-0.70 chromium 0.30-1.40 nickel 0.60-1.90 molybdenum 0.10-0.50 vanadium no more than 0,15 copper no more than 0,35 sulfur no more than 0,012 phosphorus no more than 0,010 iron rest,
and for the back sheet of steel of the following chemical composition, wt.%:
carbon 0.15-0.35 silicon 0.10-1.20 manganese 0.15-0.70 chromium 0.30-1.40 nickel 0.60-1.90 molybdenum 0.10-0.50 vanadium no more than 0,15 copper no more than 0,35 sulfur no more than 0,012 phosphorus no more than 0,010 iron rest,
hardening of the front and back sheets is carried out immediately after rolling from a temperature of no higher than 750 ° C and 850 ° C, respectively, tempering of the front sheet is carried out at a temperature of not higher than 180 ° C with a holding time of not more than 8 hours, and tempering of the back sheet is carried out at a temperature of no higher than 230 ° C with an exposure of not more than 6 hours 2. The method according to claim 1, characterized in that the steel front and back sheets are subjected to hot rolling to a thickness of approximately 0.3 and 0.5 parts of the caliber diameter of armor-piercing bullets, respectively.