CN101624681A - Ultra-high strength bainite armour steel and manufacturing method thereof - Google Patents

Abstract

The invention relates to ultra-high strength bainite armour steel and a manufacturing method thereof. The technical proposal is as follows: the casting billet comprises the following chemical components: 0.70-1.10wt% of C, 1.20-1.80wt% of Si, 1.60-2.20wt% of Mn, 1.00-1.60wt% of Cr, 0.10-0.60wt% of Mo, 0.05-1.20wt% of Al, 0.05-0.50wt% of Co, P less than 0.015wt%, S less than 0.010wt% and the balance Fe and inevitable impurities. The method is characterized by carrying out die casting or continuous casting after steel making and refining; soaking the casting billet at the temperature of 1150-1250 DEG C for 2.0-3.0h, hot rolling and cooling the casting billet; austenitizing the casting billet at the temperature of 850-1050 DEG C for 0.2-0.6h; then insulating the casting billet at the temperature of 200-500 DEG C in the nitrogen atmosphere for 10.0-240.0h, or insulating the casting billet at the temperature of 200-500 DEG C in the nitrogen atmosphere and in the strong magnetic field of 8-12T for 1.0-4.0h and cooling the casting billet. The invention has the characteristics of low cost and simple process, and the manufactured steel plates have good properties.

Description

A kind of ultra-high-strength bainite armor steel and its manufacturing method

technical field

The invention belongs to the technical field of steel for armor. In particular, it relates to an ultra-high-strength bainite armor steel and a manufacturing method thereof.

Background technique

Armor types include steel armor, aluminum alloy armor, titanium alloy armor, composite material armor, ceramic armor, explosive reactive armor, and composite armor composed of multiple material armors. At present, great progress has been made in the research on the strength, hardness, notched impact toughness and ballistic limit of armor materials, but there are the following problems:

(1) At present, although there are many types of armor steel, they are basically medium-carbon alloy steel. If you want to continue to increase the hardness, although the strength will increase accordingly, its impact toughness and fracture toughness will decrease sharply, so that it cannot withstand the huge energy of the shell. Impact load, resulting in fragmentation and collapse; the manufacturing process is complicated, the cost is too high, and the comprehensive mechanical properties are not particularly good. Such as "a multi-layer armor protection system" (CN101216272), "armor material" (CN1037321), "manufacturing and application method of multi-purpose armor plate" (CN1461937), "armor plate" (CN1952587), "high tensile strength Hot-rolled martensitic steel plate at 1000MPa and its manufacturing method" (CN101008066) and other patented technologies.

(2) For aluminum alloy armor, the hardness suitable for armored vehicles is relatively high, but it is prone to fracture due to stress corrosion; the fragmentation strength of aluminum is lower than that of steel armor, and it is easier to "scar". In addition, the melting point of aluminum To be lower than steel, it is easy to soften at high temperature and the particles of aluminum are easy to burn. Such as "a heat treatment method for aluminum-based copper alloy armor plate" (CN100999809), "a thermal processing process for aluminum-based copper alloy armor plate" (CN100999798), "a refined steel cast aluminum armor door" (CN201125637) and other patented technologies .

(3) For titanium alloy armor, under certain loading conditions, because the projectile only needs to consume very little energy to cause shear failure cracks and form fatal bottom knots, this defect cannot be ignored; titanium is expensive , use on armored fighting vehicles has been limited by cost. Such as "high-strength and high-toughness titanium alloy" (CN1031569), "manufacturing method of titanium alloy with high titanium content" (CN1044958), "high-strength titanium alloy and its preparation method" (CN1639366), "high-strength low-alloy titanium alloy and Its manufacturing method" (CN1530454) and other patented technologies.

(4) For composite material armor, there will be obvious cracking and delamination in a large area at the bonding of the armor panel and the back plate, causing the armor to lose the ability to continue to resist bullets in a larger area, thus greatly affecting the armor The ability to resist multiple bullets has shown obvious deficiencies in the anti-ballistic performance. Such as "composite armor plate" (CN1278324), "a kind of composite material bulletproof load-bearing armor plate" (CN2573990), "armor composite material" (CN1429148), "a kind of ceramic ball/resin composite material armor plate and its preparation method" (CN1948888) and other patented technologies.

(5) For ceramic material armor, because it is too brittle, the fracture toughness is extremely poor, and because of its fragility, the armor material does not have the ability to withstand multiple hits and penetrations, and the production process of this technology is complex, with many links and high production costs , they are usually only used to form an integral part of the armor system. Such as "preparation method of light boron carbide armor ceramics" (CN1541981), "production method of metal oxide composite material, metal oxide composite material powder and ceramic material" (CN1049485), "nitrogen-based ceramic material" (CN85101384), "New ceramic material and its preparation method" (CN85101457) and other patented technologies.

(6) For air-cooled bainitic steel armor without heat treatment or less heat treatment, the structure is bainite/martensite multiphase structure, the fracture toughness is lower than that of tempered martensite at the same yield strength, and the strength is not particularly high. The toughness is not particularly good. Such as "medium-low carbon manganese series air-cooled bainite steel" (CN1477226), "medium carbon and medium-high carbon manganese series air-cooled bainite steel" (CN1477225), "multivariate microalloyed air-cooled bainite steel" (CN1189542), "High-strength toughness and high hardenability air-cooled bainite steel" (CN1078269), "medium carbon air-cooled manganese-boron bainite steel" (CN86103008), "medium-high carbon air-cooled manganese-boron bainite steel" (CN86103009), "low carbon Air-cooled granular bainite steel" (CN85100080) and other patented technologies.

(7) For general medium (ultra) low carbon bainitic steel armor, the carbon content is not high, the main alloying elements Si, Mn, Cr, and Mo content are small, and the bainite transformation temperature is high. In this technology, the alloys Al, Co There is little or no content, the bainite transformation time is very long, the production process is complicated, there are many links, and the production cost is high; the toughness and plasticity are good, but the strength generally does not exceed 1500MPa. Such as "low carbon bainite steel and its preparation method" (CN101104906), "a preparation method of ultra-high strength ultra-low carbon bainite steel" (CN1916195), "high tensile strength, high toughness, low yield strength bainitic steel and its production method" (CN1786246), "an ultra-low carbon bainitic steel and its production method" (CN1521285), "a high-strength micro-alloyed low-carbon bainitic steel and its production method" ( CN101230444), "improved carbide-free bainitic steel and its production method" (CN1175980), "high-strength and high-toughness bainitic steel" (CN1036231) and other patented technologies.

It can be seen from the above analysis that:

(1) All kinds of armor materials are high-strength grades (1000-1500MPa), and ultra-high-strength grades are not involved.

(2) Various armor materials use precious alloy elements Ni or Ti, etc., and the alloy cost is high.

(3) It is difficult to match the strength, toughness and elongation properties of various armor materials at the same time.

(4) The manufacturing and processing techniques of various armor materials are complicated.

Contents of the invention

The present invention aims to overcome the above-mentioned technical defects, and aims to provide an ultra-high-strength bainite armor steel with low cost, simple process and excellent performance and its manufacturing method.

In order to achieve the above object, the technical solution adopted by the present invention is: either molten iron, or scrap steel, or molten iron and scrap steel are subjected to steelmaking and refining, followed by die casting or continuous casting, hot rolling and heat treatment.

The chemical composition and content of the slab are: C is 0.70-1.10wt%, Si is 1.20-1.80wt%, Mn is 1.60-2.20wt%, Cr is 1.00-1.60wt%, Mo is 0.10-0.60wt%, Al is 0.05-1.20wt%, Co is 0.05-0.50wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities.

The sum of the contents of Si, Mn, Cr, Mo, Al and Co in the slab is less than 6.00wt%.

The process of hot rolling and heat treatment is as follows: first soak the billet at 1150-1250°C for 2.0-3.0 hours, hot-roll, and cool naturally; then place the cooled steel plate at 850-1050°C Solidify for 0.2-0.6 hours; then keep warm for 10.0-240.0 hours under the condition of 200-500°C and nitrogen atmosphere, and cool down to room temperature with the furnace, or keep warm under the conditions of 200-500°C, nitrogen atmosphere and 8-12T strong magnetic field 1.0 hours to 4.0 hours, cool down to room temperature with the furnace.

Owing to adopting above-mentioned technical scheme, the present invention is based on cheap Si, Mn, Cr element, only has a small amount of elements such as Mo, Co, Al, so cost is low; The technology is simple.

The microstructure of the armor steel produced by the invention is that the nanoscale (20-40nm thickness) bainitic ferrite lath is the matrix, and the ultrafine structure of the retained austenite is diffusely distributed. Bainitic ferrite is a solid solution of supersaturated carbon, similar to martensite structure, with high strength, toughness and fracture resistance; austenite is a tough phase, distributed on bainitic ferrite lath Or between the slats, plastic deformation will occur under the action of external force, absorb and consume energy, and delay the expansion of cracks, which is extremely beneficial to improving the toughness of the plate. When the stress is large, a phase change-induced plastic effect (TRIP effect) will occur ), further improving the strength and toughness of steel. Due to the solid solution strengthening of carbon, dislocation strengthening, bainite lath strengthening, induced plastic strengthening, etc., the mechanical properties of bainitic armor steel can reach a higher strength level in the rolled state.

After heat treatment and strong magnetic field treatment, the steady-state strong magnetic field can transfer high-intensity energy to the atomic scale of the material without contact, change the arrangement, matching and migration of atoms, and accelerate the transformation of bainite. organization and performance. Thereby, the ultra-high-strength bainite armor steel with tensile strength of 1700-2300MPa, hardness of 530-680HV, elongation of 17-26% and fracture toughness of 26-35MPam ^1/2 can be obtained.

Therefore, the present invention has the characteristics of low cost and simple process, and the prepared steel plate has excellent performance, and is widely used in steel plates for the manufacture of enemy fighters, attack aircraft, bombers, armed helicopters, tanks, armored vehicles and ships, and can also be used in public security Steel plates for the manufacture of explosion-proof vehicles and cash transport vehicles.

Detailed ways

The present invention will be further described below in combination with specific embodiments, which are not intended to limit the protection scope of the present invention.

Example 1

A method for manufacturing ultra-high strength bainite armor steel. The chemical composition and content of the slab are: C is 0.90-1.10wt%, Si is 1.50-1.80wt%, Mn is 1.60-1.90wt%, Cr is 1.30-1.60wt%, Mo is 0.30-0.60wt%, Al is 0.05-0.60wt%, Co is 0.05-0.20wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. Wherein: the sum of the contents of Si, Mn, Cr, Mo, Al and Co in the slab is less than 6.00wt%.

After molten iron is made and refined, die casting, hot rolling and heat treatment are carried out. The process of hot rolling and heat treatment is as follows: First, soak the billet at 1200-1250°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 850-950°C for 0.4 ~0.6 hours; then keep it warm for 120.0~240.0 hours under a nitrogen atmosphere at 200~350°C, and cool to room temperature with the furnace.

The ultra-high-strength bainite armor steel manufactured in this embodiment has a tensile strength of 2100-2300 MPa; a hardness of 650-680 HV; an elongation of 21-24%; and a toughness of 28-32 MPam ^1/2 .

Example 2

A method for manufacturing ultra-high strength bainite armor steel. The chemical composition and content of the slab are: C is 0.90-1.10wt%, Si is 1.50-1.80wt%, Mn is 1.60-1.90wt%, Cr is 1.30-1.60wt%, Mo is 0.30-0.60wt%, Al is 0.60-1.20wt%, Co is 0.20-0.50wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. Wherein: the sum of the contents of Si, Mn, Cr, Mo, Al and Co in the slab is less than 6.00wt%.

After steelmaking and refining, scrap steel is subjected to continuous casting, hot rolling and heat treatment. The process of hot rolling and heat treatment is as follows: First, soak the billet at 1200-1250°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 850-950°C for 0.4 ～0.6 hours; then keep warm for 2.0 hours～4.0 hours under the condition of 200～350℃, nitrogen atmosphere and 10～12T strong magnetic field, and cool down to room temperature with the furnace.

The ultra-high-strength bainite armor steel produced in this embodiment has a tensile strength of 2000-2200 MPa, a hardness of 610-640 HV, an elongation of 17-20%, and a toughness of 26-30 MPam ^1/2 .

Example 3

A method for manufacturing ultra-high strength bainite armor steel. The chemical composition and content of the slab are: C is 0.70-0.90wt%, Si is 1.20-1.50wt%, Mn is 1.90-2.20wt%, Cr is 1.00-1.30wt%, Mo is 0.10-0.30wt%, Al is 0.05-0.60wt%, Co is 0.05-0.20wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. Wherein: the sum of the contents of Si, Mn, Cr, Mo, Al and Co in the slab is less than 6.00wt%.

After molten iron and scrap steel are made and refined, continuous casting, hot rolling and heat treatment are carried out. The process of hot rolling and heat treatment is: first soak the billet at 1150-1200°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 950-1050°C for 0.2 ~0.4 hours; then keep it warm for 10.0~120.0 hours under a nitrogen atmosphere at 350~500°C, and cool to room temperature with the furnace.

The ultra-high-strength bainite armor steel manufactured in this embodiment has a tensile strength of 1800-2000 MPa; a hardness of 570-600 HV; an elongation of 23-26%; and a toughness of 30-34 MPam ^1/2 .

Example 4

A method for manufacturing ultra-high strength bainite armor steel. The chemical composition and content of the slab are: C is 0.70-0.90wt%, Si is 1.20-1.50wt%, Mn is 1.90-2.20wt%, Cr is 1.00-1.30wt%, Mo is 0.10-0.30wt%, Al is 0.60-1.20wt%, Co is 0.20-0.50wt%, P<0.015wt%, <0.010wt%, and the rest is Fe and unavoidable impurities. Wherein: the sum of the contents of Si, Mn, Cr, Mo, Al and Co in the slab is less than 6.00wt%.

After molten iron is made and refined, die casting, hot rolling and heat treatment are carried out. The process of hot rolling and heat treatment is: first soak the billet at 1150-1200°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 950-1050°C for 0.2 ～0.4 hours; then keep warm for 1.0 ～ 3.0 hours under the conditions of 350～500 ℃, nitrogen atmosphere and 8～10T strong magnetic field, and cool down to room temperature with the furnace.

The ultra-high-strength bainite armor steel manufactured in this embodiment has a tensile strength of 1700-1900 MPa; a hardness of 530-560 HV; an elongation of 9-22%; and a toughness of 32-35 MPam ^1/2 .

This specific embodiment is based on cheap Si, Mn, Cr elements, only a small amount of elements such as Mo, Co, Al, so the cost is low; with rolling + normalizing + quenching hot rolling and heat treatment process, the process Simple.

The microstructure of the armor steel produced in this specific embodiment is nanoscale (20-40nm thickness) bainitic ferrite lath as the matrix, and the ultrafine structure of retained austenite dispersedly distributed. Bainitic ferrite is a solid solution of supersaturated carbon, similar to martensite structure, with high strength, toughness and fracture resistance; austenite is a tough phase, distributed on bainitic ferrite lath Or between the slats, plastic deformation will occur under the action of external force, absorb and consume energy, and delay the expansion of cracks, which is extremely beneficial to improving the toughness of the plate. When the stress is large, a phase change-induced plastic effect will occur, further improving the strength and toughness of steel. After heat treatment and strong magnetic field treatment, an ultra-high-strength bainite armor steel with a tensile strength of 1700-2300MPa, a hardness of 530-680HV, an elongation of 17-26% and a fracture toughness of 26-35MPam ^1/2 is obtained.

Therefore, the present invention has the characteristics of low cost and simple process, and the prepared steel plate has excellent performance, and is widely used in steel plates for the manufacture of enemy fighters, attack aircraft, bombers, armed helicopters, tanks, armored vehicles and ships, and can also be used in public security Steel plates for the manufacture of explosion-proof vehicles and cash transport vehicles.

Claims (4)

1, a kind of manufacture method of ultra-high strength bainite armour steel, it is characterized in that or with molten iron with steel scrap or with molten iron and steel scrap after steel-making and refining, carry out die casting or continuous casting, hot rolling and thermal treatment;

The chemical ingredients and the content thereof of strand are: C is 0.70～1.10wt%, Si is 1.20～1.80wt%, Mn is 1.60～2.20wt%, Cr is 1.00～1.60wt%, and Mo is 0.10～0.60wt%, and Al is 0.05～1.20wt%, Co is 0.05～0.50wt%, P＜0.015wt%, S＜0.010wt%, all the other are Fe and unavoidable impurities.

2, the manufacture method of ultra-high strength bainite armour steel according to claim 1 is characterized in that described hot rolling and process of thermal treatment are: earlier with strand soaking 2.0～3.0 hours under 1150～1250 ℃ of conditions, hot rolling, naturally cooling; Again with cooled steel plate austenitizing 0.2～0.6 hour under 850～1050 ℃ of conditions; Under 200～500 ℃ of conditions, in nitrogen atmosphere, be incubated 10.0～240.0 hours then, cool to room temperature with the furnace, or insulation 1.0 hours～4.0 hours under the condition of 200～500 ℃, nitrogen atmosphere and 8～12T high-intensity magnetic field, cool to room temperature with the furnace.

3, the manufacture method of ultra-high strength bainite armour steel according to claim 1 is characterized in that described Si, Mn, Cr, Mo, Al and the Co content sum in strand is less than 6.00wt%.

4, according to the ultra-high strength bainite armour steel of the manufacture method manufacturing of each described ultra-high strength bainite armour steel in the claim 1～3.