RU2520247C1 - High-strength armour steel and production of sheets thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed steel contains components in the following ratio in wt %: carbon - 0.28-0.40, silicon - 0.80-1.40, manganese - 0.50-0.80, chromium - 0.10-0.70, nickel - 1.50-2.20, molybdenum - 0.30-0.80, aluminium - 0.005-0.05, copper - not over 0.30, sulphur - not over 0.012, phosphorus - not over 0.015, iron making the rest. Molybdenum-to-carbon ratio makes 0.8-2.0. Steel blanks are heated to hot deformation temperature to carry out rolling at specified reduction and to quench with tempering. Quenching is performed at press with cooling in water at the pressure of 150-500 kg/cm² and water flow rate of 0.2-0.5 m³/h.

EFFECT: higher bullet-proof properties.

4 cl, 2 tbl

Description

The invention relates to the field of production of high-strength armor plate steel used for the manufacture of lightly armored vehicles, parts of the armor of stationary objects and personal protective equipment.

High-strength materials have their own specific behavior under dynamic loads and must have high values of tensile strength and yield strength of the metal, which are determined by the morphology of the formed microstructure after heat treatment.

The known compositions of high-strength armor steels [1-3] do not provide the necessary properties for comprehensive protection against new weapons due to the unbalanced content of carbide-forming and non-carbide-forming alloying elements in steels with respect to carbon, which leads to the formation of martensite of undesirable morphology and substructure, either an insufficient level of cementite doping or the formation of large special carbides that adversely affect the properties of the armor.

An analogue of the invention is steel [4], having the following composition, wt.%:

carbon 0.4-0.7 silicon 0.5-1.5 manganese 0.3-1.5 chromium 0.1-2.0 nickel 1.0-5.0 molybdenum 0.2-1.0 iron rest

Known steel armor does not provide during heat treatment the necessary stable complex of strength and plastic properties of metal and technical characteristics of protective equipment. Sheet steel has low survivability due to the tendency to brittle fracture due to the high content of carbon and carbide-forming elements up to 2.0% of the mass.

An analogue of the invention is also high-strength armor plate steel for protection against bullets TUS [5], which contains components in the following ratio:

carbon 0.44-0.48 silicon 1.2-1.6 manganese 0.3-0.6 chromium 1.3-1.7 nickel 1.4-1.8 molybdenum 0.2-0.4 iron rest

A disadvantage of the known armor steel is the high carbon and chromium content, during which heat treatment produces special chromium carbides of the type (Fe, Cr) ₇ C ₃ at dislocations, followed by their coalescence along the boundaries of austenitic grain and martensite, which increase the tendency of steel to brittle fractures and reduce armor resistance of steel.

An analogue of the invention is armored heat-resistant welded steel [6], having the following composition, wt.%:

carbon 0.001-0.41 silicon 0.10-2.6 manganese 0.10-1.8 chromium 0.10-8.6 nickel 0.10-1.9 molybdenum 0.10-0.6 cobalt 0.05-4.6 copper 0.10-1.9 sulfur no more than 0,004 phosphorus no more than 0,008 iron rest

The disadvantage of this steel is that the achieved level of armor-protecting properties is ensured only by additional alloying with expensive components, such as cobalt, which is introduced in an amount of up to 4.6 wt.%, Nickel and copper - up to 1.9 wt.% With a high silicon content ( up to 2.6 wt.%) and chromium (up to 8.6 wt.%). This significantly increases the cost of armor steel (by 20% - 30% per ton) and its use becomes economically impractical. In addition, steel is a difficult material in technological use, which leads to low stability of armor-protecting properties, a high level of rejection and additional costs in its production.

The closest analogue of the claimed high-strength armor plate steel for protection is armor steel [7], having the following composition:

carbon 0.45-0.50 silicon 0.17-0.40 manganese 0.60-0.80 chromium 1.0-1.3 nickel 1.20-1.5 molybdenum 0.25-0.35 vanadium 0.08-0.15 copper 0.1-0.2 sulfur 0.005-0.01 phosphorus 0.003-0.01 zirconium 0.005-0.01 tungsten 0.01-0.05 iron rest

The use of the well-known article as armor is possible only in a thickness of more than 15 mm, when the energy consumption during shelling is determined by the high specific gravity of the protective armor, and the microstructure is a secondary factor characterizing the material in this process.

The indicated chromium and molybdenum content in known steels does not allow obtaining the structure of low tempered martensite with high ductility and low tendency to brittle fracture after heat treatment, which leads to a decrease in the bulletproof and anti-fragmentation resistance of the armor, since chromium and molybdenum carbides with a high doping level are formed during heat treatment the boundaries of martensite crystals and the initial austenite grain, thereby increasing the embrittlement of the metal at high speed loads.

The objective of the invention is to provide bulletproof resistance of sheet armor made of medium alloy steel with a doping level that provides a balanced ratio of carbide-forming elements to carbon, and the formation of a carbide phase based on doped cementite and a submicrostructure of martensite during heat treatment of sheet metal to achieve a strength to ductility ratio σ _in / σ _0.2 > 1.1.

The problem is solved due to the fact that we offer high-strength armor steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminum, copper, sulfur, phosphorus and iron in the following ratio of components, wt.%:

carbon 0.28-0.40 silicon 0.80-1.40 manganese 0.50-0.80 chromium 0.10-0.70 nickel 1,50-2,20 molybdenum 0.30-0.80 aluminum 0.005-0.05 copper no more than 0.30 sulfur no more than 0,012 phosphorus no more than 0.015 iron rest

The technical result of the invention is to increase the bulletproof resistance and survivability of sheet armor even in sheets with a thickness of less than 10 mm, which is achieved due to the fact that the content of carbide-forming elements (silicon, chromium and molybdenum) with respect to carbon is balanced to a level at which, when heat treating sheet metal rolled products (rolling with low tempering), alloyed cementite is formed with the subsequent precipitation of carbides in the volume of martensite crystals within the primary coherent austenitic grain a metal matrix, which greatly reduces the tendency to brittle fracture armor, leads to the formation of the microstructure morphology lath martensite, having high strength and ductility and, as a consequence, high power consumption at high loads leaf armor.

When the carbon content is less than 0.28 wt.%, The degree of tetragonality of the martensite lattice is insufficient to form the necessary martensite substructure during quenching, which provides high hardness and strength of the armor.

When the carbon content is more than 0.40 wt.%, Non-stoichiometric carbon carbides and twin martensite with a high tendency to brittle fracture and low viscosity are formed in the metal structure during the hardening of medium alloyed steel, which will lead to the nucleation and development of cracks in the process of manufacturing armor (editing, stamping, etc.) and its operation.

Nickel enhances the ductility and toughness of hardened metal and accelerates the coalescence of carbides, shifting it to lower temperatures compared to unalloyed steel. When the nickel content of more than 2.20 wt.% There is an intense coalescence of carbides and their growth to sizes that reduce the positive effect of nickel on ductility. In addition, residual austenite appears in the microstructure of rack martensite, which further reduces ductility and increases the tendency of steel to brittle fracture during sheet production and its armor resistance worsens (decreases). When the nickel content is less than 1.5 wt.%, The ductility of the metal is reduced due to an insufficient level of alloying.

The introduction of sulfur, phosphorus, aluminum, and copper into the composition of the armored steel according to the invention within the stated limits helps to achieve stability of high strength and plastic properties, since when quenching, fine grain is formed with minimal resistance to phase transition processes.

The closest technology for the production of sheet metal from steel is the method [7], which consists in heating the billets to a hot deformation temperature, followed by rolling with regulated compression and hardening with tempering, while the heated billets are subjected to hot forging at a temperature of 1100-800 ° С , isothermal annealing at a temperature of 630-670 ° C with cooling in a furnace and reheating for rolling to a temperature of 1050-1100 ° C in a furnace with a neutral atmosphere, and after quenching with tempering, additional tempering, etc. than rolling is performed at a temperature of 1100-800 ° C with the total rolling reduction of not less than 80%.

The disadvantage of this method is the complexity of the technology, which consists in multi-stage, as well as high energy consumption due to the fact that a number of stages require a high temperature.

The challenge faced by the invention relating to the technology of production of sheet metal, is to simplify the process of rolling the proposed sheet material.

A method of producing sheet metal according to the invention consists in heating the preforms to a hot deformation temperature, followed by rolling with regulated compression and tempering with tempering, while the steel is quenched in a press under a pressure of 150-500 kg / cm ² and cooled with water at a water flow rate of 0 , 2-0.5 m ³ / hour

The invention can be illustrated by the following examples.

High-strength medium alloyed armored steel was smelted in an electric arc furnace with a capacity of 150 tons, followed by slag treatment in a ladle. Steel was cast on a continuous casting plant into billets with a section of 180 × 250 mm with a weight of up to 25 tons, which were rolled onto a sheet with a thickness of 2-20 mm. Then, the blanks of the rolled sheet were subjected to heat treatment, including quenching in a press under a pressure of 250 kg / cm ² with cooling with water at a water flow rate of 0.3 m ³ / h and low tempering was carried out at a temperature of 150-250 ° C in an oven.

The composition of the steel of various swimming trunks is presented in Table 1.

The ratio of molybdenum to carbon is maintained in the range of mass% 1.0-2.0.

Preferably, an increased molybdenum content with an average carbon content and a molybdenum / carbon ratio in the range of 0.8-1.2 wt.%, While the chromium content is preferably at the level of 0.2-0.3 wt.%. In this case, the formation of twin martensite is suppressed, and its volume fraction does not exceed 5% of the dispersed substructure of rack martensite. Heat treatment modes are selected taking into account the thickness of the armor sheet, which varied from 2.3 to 6.5 mm. Testing cards, according to the normative documentation (GOST R 50963), were cut out of a sheet of steel according to the invention after final heat treatment and were fired by 7.62 mm caliber bullets at a speed of 435 m / s and the number of shots 4-6. The results of tests for bulletproof resistance are given in table.2.

All lesions for the proposed steel composition were conditioned. On the cards made of steel according to the prototype, after testing under similar conditions, cracks and spalls were found on the back side.

From the above data it follows that in the proposed high-strength armor plate steel, the level of technical properties is increased due to the combination of high strength and plastic properties and increased resistance to crack development due to the balanced level of steel alloying, providing the formation of a highly dispersed microstructure with the morphology of rack martensite and carbides based on alloyed cementite evenly distributed over the submicrostructure.

Experience in the manufacture of steel armor of the proposed composition shows that the production process is more technological and simple in comparison with the prototype.

Table 1 Composition number The content of alloying and impurity elements, wt.% C Si Mn Cr Ni Mo Al Cu S P one 0.28 0.80 0.50 0.10 1,50 0.30 0.005 0.10 0.004 0.005 2 0.32 0.85 0.57 0.20 1,66 0.27 0.016 0.15 0.006 0.006 3 0.35 1.16 0.66 0.27 1.87 0.34 0,027 0.17 0.007 0.008 four 0.38 1.30 0.71 0.42 2.15 0.46 0,040 0.25 0.009 0.013 5 0.41 1.42 0.81 0.52 2.25 0.51 0,055 0.32 0.013 0.016 6 0.30 0.75 0.76 0.15 1.85 0.48 0,025 0.17 0.004 0.006 7 0.31 0.76 0.78 0.45 1.83 0.23 0,027 0.19 0.005 0.007 8 0.39 1.32 0.54 0.27 1,56 0.31 0,028 0.21 0.005 0.005 9 0.38 1.34 0.57 0.30 2.15 0.46 0,031 0.24 0.006 0.008 10 0.34 1.17 0.78 0.31 1.72 0.37 0,035 0.25 0.007 0.009 eleven 0.35 1.13 0.67 0.29 1.75 0.39 0,028 0.23 0.005 0.011 The analogue of 2400558 No. 13 0.28 1,60 0.40 0.30 0.85 2.0 Co 3.30 0.45 0.003 0.004 Prototype according to 2456368 0.34 0.23 0.50 1.84 2.02 0.84 0.015 0.29 0.002 0.011

table 2
The results of the bulletproof tests were carried out in accordance with GOST R 50963. The average bullet speed when firing the cards was respectively: TT pistol (7.62 mm cartridge with PST bullet) - 435 m / s Card number Sheet thickness mm Lesion score Cards of the invention 103 2.40 conditioning 2.40 conditioning 2.40 conditioning 135 2,35 conditioning 2,35 conditioning 2.35 conditioning 746 2.60 conditioning 2.60 conditioning 2.60 conditioning 733 2.65 conditioning 2.65 conditioning 2.65 conditioning Prototype cards one 2.40 breaking through 2 2,35 breaking through 3 2,35 breaking through

List of sources of information

1. RU 2236482 C1, C22C 38/46, publ. September 20, 2004

2. RU 2236482 C1, C22C 38/46, publ. September 20, 2004

3. JP 2006-070327 C22C 38/00, publ. 03/16/2006

4. US 5122336, C22C 38/44, publ. 06/16/1993

5. RU 2185459, C1, C22C 38/44, publ. July 20, 2002

6. RU 2400558, C22C 38/58, publ. 09/27/2010

7. RU 2456368, C22C 38/50, publ. 07/20/2012

8. US 5122336, C22C 38/44, publ. June 16, 1992

Claims (4)

1. High-strength armor plate steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminum, copper, sulfur, phosphorus and iron, characterized in that it contains components in the following ratio, wt.%:
carbon 0.28-0.40 silicon 0.80-1.40 manganese 0.50-0.80 chromium 0.10-0.70 nickel 1,50-2,20 molybdenum 0.30-0.80 aluminum 0.005-0.05 copper no more than 0.30 sulfur no more than 0,012 phosphorus no more than 0.015 iron rest
the ratio of molybdenum / carbon is 0.8-2.0. 2. Steel according to claim 1, characterized in that the chromium content in the composition is at the level of 0.2-0.3 wt.%. 3. Steel according to claim 1, characterized in that the ratio of molybdenum / carbon in the composition is at a level of 0.8-1.2. 4. A method of manufacturing sheet metal from high-strength armor steel according to claim 1, comprising heating the billets to a hot deformation temperature, followed by rolling with regulated compression and tempering with tempering, wherein the quenching is carried out in a press with water cooling at a pressure of 150-500 kg / cm ² and at a flow rate of 0.2-0.5 m ³ / hour.