WO2024205466A1

WO2024205466A1 - Breech block for a firing device and method for the manufacturing of a breech block for a cannon

Info

Publication number: WO2024205466A1
Application number: PCT/SE2024/050233
Authority: WO
Inventors: Martin PERKOVIC; Erik PERKOVIC; Fredrik THUVANDER
Original assignee: BAE Systems Bofors AB
Current assignee: BAE Systems Bofors AB
Priority date: 2023-03-30
Filing date: 2024-03-14
Publication date: 2024-10-03
Anticipated expiration: 2025-09-30
Also published as: SE547036C2; SE2300025A1

Abstract

The present invention relates to a method for manufacturing a breech block (1) for a cannon, where the method comprises raw material for the breech block (1) being manufactured from at least two different metal powders, a bulk material (20) and a surface capsule (10), so that the surface capsule (10) is arranged so as to enclose bulk material (20), and where the surface capsule (10) is manufactured additively, after a raw material for the breech (1) has been manufactured, the raw material is post-processed for the manufacture of the breech (1). The invention further relates to a breech block and a firing device comprising a breech block.

Description

BREECH BLOCK FOR A FIRING DEVICE AND METHOD FOR THE MANUFACTURING OF A BREECH BLOCK FOR A CANNON

TECHNICAL AREA

[0001 ] The present invention relates to a method for manufacturing a breech block for a firing device, where the method includes that a raw material for the breech block is manufactured from at least two different metal powders, a bulk material, and a surface coating, in such a way that the surface coating is arranged so as to enclose bulk material and entails the surface coating being manufactured additively. Once a raw material for a breech block has been manufactured, the raw material is post-processed for the manufacture of the breech block. The invention further relates to a breech block and a firing device comprising a breech block.

BACKGROUND OF THE INVENTION, PROBLEM STATEMENT AND PRIOR ART

[0002] Launchers, such as barrel-based weapons, such as cannons and guns, are fired by burning gunpowder and thereby creating a gas expansion, where the gas expansion moves a projectile in a barrel. The breech mechanism is a common mechanism for launchers such as cannons, especially automatic cannons. A central component of the breech mechanism is a nearly rectangular block of metal, also called a wedge or breech block, which can slide inside a groove in the firing device, with the rear part of the piece being perpendicular to the longitudinal axis of the barrel. By operating the breech block perpendicularly to the barrel, an opening to the chamber of the barrel can be created so that an ammunition unit can be arranged in the chamber, after which the breech block can be maneuvered so that it is arranged behind the ammunition unit and thereby locks the ammunition unit inside the barrel, after which the ammunition unit can be fired. Preferably, a firing pin is arranged in the breech block which can strike an igniter arranged in the ammunition unit which initiates the propellant charge in the ammunition unit. The breech design allows for a high rate of fire, but it is not gas-tight, which means that the propellant charge must be enclosed in a casing. When the piece is to be loaded, the breech block is moved to the side, this movement being powered by hand or machine, and an ammunition unit is inserted into the chamber. In a common embodiment, the casing of the ammunition unit hits ejectors which are arranged on both sides of the cartridge position/chamber, and this releases a latch which closes the breech. Once the ammunition unit is fired, the breech block mechanism is opened once again, usually by means of the recoil force. The mechanism is designed so that the breech block pushes the ejectors backwards as it slides away so that the empty casing is ejected. Then the process can be initiated again so that an autocannon can be provided which repeatedly, in succession, fires ammunition units. Each ammunition unit is arranged with a projectile and propellant arranged in a casing. An ignition device is arranged inside the casing, often including an ignition cap that is able to ignite the propellant charge. As an alternative to an ignition cap, the propellant charge can be ignited by means of, for example, an electrical pulse or a laser.

[0003] Examples of manufacturing methods for breeches or other end piece components are given in patent document CN 110893503 A, which describes a method for manufacturing components through an additive manufacturing method including arc welding.

[0004] The above known technology does not demonstrate that additive manufacturing methods including powder are used.

[0005] Further problems that the present invention intends to solve are shown in alongside the subsequent detailed description of the various embodiments.

PURPOSE OF THE INVENTION AND ITS CHARACTERISTICS [0006] The purpose of the present invention is to achieve an improved way of manufacturing a breech block consisting of at least two different metals where a core of a metal with certain properties is coated with another metal adapted to be compatible with other metal components included in the firing device.

[0007] The invention relates to a method for manufacturing a breech block for a cannon, where the method comprises a raw material for the breech block being made from at least two different metal powders, a surface capsule made from a first metal powder and a bulk material made from a second metal powder, so that the surface capsule is arranged so as to enclose bulk material, and where the surface capsule is manufactured additively. Once a raw material for a breech block has been manufactured, the raw material is post-processed for the manufacture of the breech block.

[0008] According to further aspects for the method of manufacturing a breech block according to the invention apply;

[0009] that bulk material is additively arranged in raw material for the breech block.

[0010] that bulk material is arranged in a surface capsule in powder form once the surface capsule has been produced additively.

[001 1 ] that post-treatment of the raw material includes subjecting the raw material to high pressure and heat, also known as hot isostatic pressing, HIP, for pressing and sintering the metal powders included in the raw material.

[0012] that post-treatment further, following hot isostatic pressing, includes heat treatment.

[0013] that post-treatment further, following hot isostatic pressing and heat treatment, includes mechanical processing of the breech block. [0014] that the surface capsule preferably consists of low-alloy NiCrMo steel.

[0015] A low-alloy NiCrMo steel is characterized by high degrees of resilience and hardness. Aforementioned high degree of hardness is required due to abrasion occurring during firing and aforementioned high resilience is quired for purposes of resisting plastic deformation. Due to the surface layer having such a high degree of resilience, properties such as ductility and toughness will be affected. Rather, the material will be somewhat brittle. For this reason, a tough core is required, as in the bulk material, made up of steel with more alloy, e.g. tool steel or martensitic stainless steel.

[0016] The low-alloy NiCrMo steel has a yield point of at least 1200 MPa and a yield point at -40 C of at least 27 J.

[0017] that the bulk material preferably consists of stainless steel or tool steel. The stainless steel or tool steel has higher levels of Cr and Ni than the low- alloy carbon steel used for the surface. The core, the bulk material, must consist of a steel with lower alloy content, e.g. a tool steel with higher levels of Cr and Ni than the low-alloy carbon steel used for the surface. A risk inherent in HIP is that every grain in the metal prior to HIP might oxidize and then lead to properties of toughness and fatigue being decreased, as the oxides of each grain lead to natural crack growth paths. Thus, steels (stainless steels/tool steels) with higher levels of Chromium are used, as they form chromium oxide and counteract this. The core material must be stainless or a tool steel and characterized by properties such as good fatigue resistance, toughness, and ductility. The materials used could be, for example:

Stainless martensitic steels; X4CrNiMo16-5-1 (1.4418), Super 13 Cr (UNS S41426)

Tool steel: X40CrMoV5-1

The stainless steel or tool steel has a yield strength of approximately 800- 900 MPa and an impact toughness at -40 °C of a minimum of 50 J. [0018] The invention further consists of a breech block with higher strength and toughness.

[0019] The invention further consists of a firing device comprising a breech block.

ADVANTAGES AND EFFECTS OF THE INVENTION

[0020] By manufacturing parts of the breech or the entire breech through additive manufacturing, one can achieve a breech or breech block with higher strength and toughness compared to currently existing technology that is based on processing of a forging blank by means of cutting. For future launch systems, where both the rate of fire and the forces acting on the breech are expected to increase, new manufacturing solutions for the breech are required to improve the properties of the breech and/or breech block.

LIST OF FIGURES

[0021 ] The invention will be described in more detail below with reference to the attached figures where:

[0022] Fig. 1 shows a breech block in cross-section, according to an embodiment of the invention.

[0023] Fig. 2 shows the method steps for manufacturing a breech block, according to an embodiment of the invention.

DETAILED EXECUTION DESCRIPTION

[0024] The present invention shows embodiments of manufacturing methods for improved breech block for firing device. [0025] A launching device, also called cannon, howitzer, or piece, such as an automatic cannon, is intended to release a projectile by means of a propellant. Preferably, a propellant, such as gunpowder, is initiated in a part of the cannon, often a chamber specifically adapted for this purpose. For the automatic cannon, the propellant is preferably arranged in a casing. Initiation takes place by igniting the propellant, for example with an ignition cartridge or an igniter in an ammunition unit, which is initiated by impact. Other methods of igniting the propellant may be by laser or electrical energy igniting the propellant. The propellant bums at high speed and large gas evolution, which creates a gas pressure in the chamber that propels the projectile out of the barrel of the firing device. The propellant is adapted so as to generate a constant pressure on the projectile, to the greatest possible extent, during the entire barrel course, when the projectile moves in the barrel, which provides the projectile with high velocity when the projectile leaves the barrel mouth. For automatic guns arranged to fire ammunition units, the projectile, igniter, and the propellant are arranged in a casing. Since the propellant is arranged in a casing, a simpler mechanism, often called a breech, can be used to seal behind the ammunition unit when the ammunition unit is arranged in the chamber of the barrel. The breech does not have a gas-tight seal against the barrel, which enables a high rate of fire, i.e. ammunition units can be exchanged at high speed by opening the breech block and enabling an ammunition unit to be fitted in the barrel and then moving the breech block so that it closes to the barrel, after which the projectile is fired from the ammunition unit, and the empty casing is subsequently removed to once again arrange an ammunition unit in the barrel.

[0026] If the breech, or other parts for firing systems, are manufactured with HIP, materials with high resistance to impact loads can be produced. Impact loads are part of the recoil forces that arise in a launch system when projectiles are fired from a barrel. It is desirable to provide a breech with higher strength and toughness compared to currently existing technology. Since the breech is part of the mechanism in a firing system, compatibility between materials used in the various components included in the firing system is assumed. If, for example, the breech is changed to a different material than other components in the launch system, there is a risk that corrosion may occur, e.g. if the degree of nobility varies between the components included in the launch system. In particular, there are risks of corrosion when it comes to pieces in a marine environment, since a conductive liquid, such as salt water, can act as a conductive liquid that can cause galvanic corrosion of the components included in the piece if the material/nobility across the components differs. Thus, it is relevant for an improved breech to have a surface coating with similar material properties as surrounding components in the launch system as the breech will be close to other components in the launch system and will also be exposed to salt water.

[0027] Through additive manufacturing of a breech based on two different metal powders, where the metal powders have different properties, an improved breech can be created. Preferably, a breech is created with a bulk substance in the core and a substance as a surface layer where the additively manufactured component undergoes Hot Isostatic Tarpaulin to eliminate pores in the part. In a first embodiment, the raw material for the breech is manufactured from an outer capsule that is manufactured additively, which is then filled with metal powder in the core. In a second embodiment, the raw material for the entire breech is additively manufactured from two metal powders.

[0028] In cases of an outer capsule, the surface capsule, being manufactured additively, filling and packing can be done by hand with the metal powder that is arranged in the core, the bulk material, inside the outer layer, the surface capsule. The outer layer is manufactured additively, preferably by means of 3D Printing, as the outer geometry of the breech is too complex to manufacture as is usually done with HIP, i.e. pressing of sheet metal and welding. Following 3D Printing of the outer geometry, the capsule, the capsule is filled with powder in an opening arranged in the surface capsule. The opening is preferably arranged in a location on the breech where external stresses on the breech are small. The HIP process is then started, which includes evacuation, vibration and sealing of the capsule construction. This is followed by HIP in oven.

[0029] Hot isostatic pressing, HIP, is a manufacturing process to control the grain size and structure of the material. HIP also enables the packing of metal, polymer, ceramic and composite powders into solid form. The benefits include removing all internal voids in metal components created by additive manufacturing methods and improving mechanical properties, such as fatigue resistance/fatigue strength, toughness, plasticity, and impact toughness. Furthermore, HIP can create a dense material from metal, composite, polymer, or ceramic powder without melting, and allows for materials with partly different characteristics to be coordinated in the same component.

[0030] With HIP, a solid material with superior properties can be created from powder as the powder/powder components have a fine, uniform grain size and isotropic structure. Furthermore, through the use of HIP, dissimilar metals can be joined without the need for temperature-limiting binders. Through HIP, several diffusion bonds can be created in a single process cycle. HIP works for a large number of metal alloys, as well as for example polymers and ceramic materials. For example, alloys including nickel, cobalt, tungsten, titanium, molybdenum, aluminum, copper and iron, oxide and nitride ceramics, glass, intermetallic substances, and polymers. HIP enables bonding and combinations of materials that cannot otherwise be combined, i.e. composites.

[0031 ] Once the bi-material part has undergone hot isostatic pressing, various forms of heat treatment can be carried out to change the mechanical properties of the breech. Following heat treatment, fine processing can be carried out such as cutting processing or grinding of the part to adapt the part based on adaptation to the firing system, if necessary. Additive manufacturing, like various forms of 3D-Printing, can be carried out, where one material is chosen for a surface layer and another material is chosen for the core, the bulk material.

[0032] The material for the surface layer preferably consists of low-alloy NiCrMo carbon steel, i.e. a steel with a lower percentage of alloy elements, with the same or similar chemical composition as adjacent parts (back piece and barrel). By choosing a steel quality with similar properties to other parts of the firing system, good material compatibility can be achieved. The core, the bulk material, consists of a different material with different properties adapted to better withstand the recoil forces acting on the breech.

[0033] A number of different methods for additive manufacturing are considered relevant such as

- Electron Beam Melting (EBM)

- Direct Laser Metal Sintering (DMLS).

[0034] With electron beam melting, EBM, the part is manufactured layer by layer in a vacuum chamber and uses an electron beam to melt metal powder fed from a holder/cartridge and distributed/spread on a platform/coordinate table. The electron beam then heats the metal powder and melts the metal powder to prepare a piece, also called a blank. Relatively high temperature is created by the electron beam, which melts the metal powder in the focal point of the electron beam. By distributing the material/melting the material based on a CAD model, a piece can be created which has a large degree of flexibility regarding geometric structure. Furthermore, several metal powders can be used for the creation of a piece consisting of several different materials. The piece is built layer upon layer.

[0035] By means of direct laser metal sintering, DMLS, the piece, also called raw material, is manufactured by heating one or more different powder materials and spreading them out in an even layer over a platform/coordinate table with a roller, after which a pulsed laser irradiates selected parts of the powder material, where a cross-section can be created by the powder particles, through the heat generated by the laser, sticking together and forming a piece. The layer thickness is 0.1 mm and powder that does not become a part of a piece can be reused.

[0036] In Fig. 1 , a breech block 1 is shown in cross-section with a bulk material 20, preferably being manufactured from stainless powder steel such as a martensitic steel and a surface capsule 10 being manufactured from a preferably low-alloy carbon steel. The bulk material 20 preferably has material properties that result in high toughness and maintained or slightly lower strength when the stresses are at their highest in the surface. The contact surface between the bulk material 20 and the surface capsule 10 is a diffusion bond that is created by means of hot isostatic pressing of the powder component/raw material. The additively manufactured component, the raw material, is arranged in an oven preferably outfitted with a connection device for the evacuation of air, vacuum pumping, before and/or during the implementation of the manufacturing method in the form of hot isostatic pressing.

[0037] Fig. 2 shows manufacturing method 100 for breech block 1 with HIP. Initially, a surface capsule is manufactured additively from a first metal powder in the step Surface capsule is manufactured additively from a first metal powder 101. One metal powder is used for the surface coating of the raw material, the surface capsule, and another metal powder is used for the bulk material, the core, of the raw material. The surface capsule is manufactured from powder with an additive manufacturing method, for example EBM or DMLS but also other currently available methods, and any future additive manufacturing methods can be used to manufacture the surface capsule. In the next step, raw material is produced by means of filling the surface capsule with a second metal powder 102. Core material is arranged in the surface capsule, e.g. by means of filling and packing material by hand. Furthermore, the entire raw material can be additively manufactured from two metal powders, a first metal powder for the surface capsule, which constitutes the surface treatment, and a second material for the core, the bulk material. In step Evacuation, vibration, closure 103, the raw material can be prepared for the next step, HIP. In the case that the raw material is manufactured in a wholly additive fashion, step 103 can be omitted as the raw material is already prepared for HIP. Hot isostatic pressing is then carried out in step HIP 104. Meaning that a gas is used to create an isostatic pressure on the raw material by connecting the gas to a connection device on the furnace. Before the gas is arranged for the oven, the oven can be vacuum-pumped or otherwise evacuated of air or of the filling gas/fluid that is present in the oven prior to evacuation, for instance by flushing with a noble gas. The entire raw material is then heated to create a preform, or a HIPPAD body. HIP temperature is preferably 20% below the melting temperature of the material. For martensitic stainless steels the HIP temperature is above the phase transformation to the austenitic state (which is on the order of 80% of the material's melting point). Once hot isostatic pressing has been carried out, the body can undergo heat treatment/hardening 106, which means that body, that has now been joined together, is heated. Following heat treatment, the material is suitable for processing, e.g. processing by means of cutting in the step Processing 108, where cutting processing such as turning or milling or grinding. Where applicable, a surface treatment 110 such as phosphating or manganese phosphating is also carried out for purposes of rust protection.

ALTERNATIVE EMBODIMENTS

[0038] The invention is not limited to the specifically shown embodiments but can be varied in various ways within the framework of the patent claims.

[0039] It is understood, for example, that the choice of materials, the choice of geometric shapes, the elements and details included in the breech or the components for the launch system are adapted to the weapon system(s), platform and other design features that are currently available. [0040] Furthermore, all forms of breeches and breech blocks and end pieces for both fine caliber, medium caliber and coarse caliber are included.

Claims

Patent Claims

1. Method for manufacturing a breech block (1 ) for a cannon, characterized in that the method comprises that a raw material for the breech block (1 ) being manufactured from at least two different metal powders, a surface capsule (10) made from a first metal powder and a bulk material (20) made from a second metal powder, so that the surface capsule (10) is arranged to enclose bulk material (20), and where the surface capsule (10) is manufactured additively, after the raw material for the breech block (1 ) has been manufactured, the raw material for the breech block (1 ) is post-processed for the manufacture of the breech block (1 ).

2. Method according to claim 1 , characterized in that bulk material (20) is additively arranged in raw material for the breech block (1 ).

3. Method according to claim 1 , characterized in that bulk material (20) is arranged in the surface capsule (10) in powder form once the surface capsule (10) has been produced additively.

4. Method according to one of the above claims, characterized in that post-treatment of the raw material includes subjecting the raw material to high pressure and heat, also called hot isostatic pressing, HIP, for pressing and sintering the metal powders included in the raw material.

5. Method according to claim 4, characterized in that further posttreatment, following hot isostatic pressing, includes heat treatment.

6. Method according to any of claims 4 - 5, characterized in that posttreatment further includes mechanical processing of the breech block, following hot isostatic pressing and heat treatment.

7. Method according to one of the above claims, characterized in that the material in the surface capsule preferably consists of low-alloy NiCrMo steel.

8. Method according to one of the above claims, characterized in that the bulk material preferably consists of stainless steel or tool steel.

9. Breech block (1 ) with higher strength and toughness manufactured according to any of claims 1 - 8

10. Firing device arranged with a breech block according to claim 9.