Powder Metallurgy
Application of powder metallurgy in military industry
Parts of powder metallurgy in the field of weapons and aerospace
Qinhuangdao Zhongwei Precision Machinery Co., Ltd. summarized the powder metallurgy parts used in aviation. The bolts used in aerospace and aerospace were originally made of high-strength plastics. However, plastic bolts cannot be used in high temperature environments. Yes, in the initial design, the material used for the bolts is plastic, so the bolts should not only be light in weight, but also cannot be reduced in high temperature strength. To this end, a powder metallurgy titanium hollow screw with a hexagonal head and a circular through hole is designed and manufactured. This hollow screw is made of cold isostatic pressing-sintering, and then the outer diameter of the fine turning and machining. Made of thread. Among them, the dome called Sidewinder Missile was previously made of a titanium alloy billet with a mass of 2.2kg, which was machined into a finished dome with a precision tolerance and a wall thickness of 0.635mm. The mass of the preform made by the powder metallurgy cold isostatic pressing-sintering process is only 0.56kg, so only the preform can save 60% of the cost compared with the previously used forged titanium alloy blank. At the same time, it also saves a lot of cutting costs and energy, which is obvious. Maverick missile lens mount made of titanium powder metallurgy. This part used to be made of blanks and machining, and the ratio of the quality of the input material to the quality of the finished part was 15:1; after switching to titanium powder metallurgy material, the ratio of the quality of the input material to the quality of the finished part was reduced to 3: 1. It saves about 80% of materials, and of course, it also greatly reduces cutting costs and energy consumption.
Titanium injection molded parts and titanium alloy powder metallurgy parts
Some powder metallurgy titanium alloy parts are produced by powder forging process. When manufacturing parts with conventional forging processes, not only the weight of the forgings is large, but also several pairs of forging dies are required. When powder forging is used, the cold isostatic pressing (or conventional pressing and forming) process is used first to mix the element powder (or pre-alloyed titanium alloy powder) and sinter into a preform (density about 95%), and then a Forging can be made into full density forgings.
Titanium keel joints for aircraft are made of titanium alloy powder by hot isostatic pressing. When manufactured by powder metallurgy isostatic pressing, compared with ordinary forgings, each part can save 1.65KG of titanium alloy, about 78.6% of material, and also save a lot of cutting costs and time resources. The industrial blunt titanium hexagon nut produced by powder metallurgy can save a lot of cost in the process of manufacturing fasteners. This powder metallurgy titanium nut accounts for the majority of the titanium hexagon nut market and is currently used in the military industry. According to literature reports. Titanium has very good corrosion resistance to seawater, and is an ideal material for ship weapons. Titanium powder green samples were tested at Wrightsvil Beach in seawater and at Kure Beach, North Carolina, in a marine atmosphere. After 15 years of exposure to seawater, titanium powder metallurgy test panels showed very good corrosion resistance. Figure 6-9 shows a sonar reflector for the US Navy made of powder metallurgy titanium alloy. This product was previously manufactured from wrought and rolled titanium alloys by machining, and as early as the 1970s, it was switched to powder metallurgy titanium alloys. Another project completed by the US Navy is to study a method for extruding powder metallurgy titanium billets into 20mm cartridge cases. This is due to the rapid corrosion of the ammunition stored in the rails to be fired on the deck exposed to the elements. The researched initial production Ding Yi has a total of 7 processes, producing powder metallurgy titanium bullet casings, and successfully completed the test shooting. Later, powder metallurgy titanium cartridges were not used due to the use of plastic and brass-coated cartridges.
For example, the nose cone of the missile was previously made of forged titanium alloy ring material by cutting, and it was produced by cold isostatic pressing sintering as early as the 1970s. Hundreds of powder metallurgy titanium alloy missile nose cones in early production passed the acceptance test. Another special use of titanium powder is as a material for the production of incendiary bombs, and both zirconium and cerium alloys have historically been used for these purposes. However, the use of titanium as a material for incendiary bombs has some advantages, such as high energy production per kilogram or cubic meter, and low cost.
Weapon powder metallurgy technology refers to the technology of using metal or other powder materials to manufacture various porous, semi-dense or fully-dense weapon parts and products through powder mixing, compacting, sintering, molding and post-processing processes. Weapon powder metallurgy technology is the key manufacturing technology for anti-tank kinetic energy armor-piercing projectile cores, missile engine nozzles, ceramic armor components, tank power transmission system friction plates and other components, including: hot isostatic pressing and cold isostatic pressing technology for special parts of weapons , sintering process, self-propagating high temperature synthesis technology, powder injection molding technology, powder forging technology, performance testing and non-destructive testing technology of powder metallurgy parts, etc. Because powder metallurgy technology has the advantages of low process cost, high material utilization rate, net shape or near-shape of the manufactured parts, especially suitable for mass production, it is used to replace the conventional manufacturing process of some weapon parts, and it can also improve product performance. , the effect of shortening the cycle, prolonging the service life and reducing the production cost.
1. Extensive research and application of powder metallurgy technology for foreign weapons
Powder metallurgy technology has been used in the fuze of US military ammunition for more than 30 years. For example, the M549, M550 bullet safety and the detent of the safety release device are all powder metallurgy brass parts; the fuze fuse of the 50mm (mm) bomb, the fuze timer shell and the fuze base of the Beehive warhead are all made of 316L stainless steel powder metallurgy. In addition, there are powder metallurgy steel parts with complex shapes in the Copperhead missile guidance system.
Powder metallurgy technology is widely used in ammunition. Such as 20mm, 50mm pure iron powder metallurgy rotating elastic belt, tungsten heavy metal powder metallurgy kinetic energy armor-piercing core, metal powder injection molding armor-piercing fin, armor-piercing ammunition-shaped cover, automatic seeking seeker powder metallurgy parts, etc., its application The quantity is very large. Russian large-caliber artillery shells also use brass powder metallurgy forming belts.
The application of powder metallurgy technology in firearms is very broad. For example, 22 kinds of parts such as the speed machine, protective tube, locking machine and latch of 12.7mm caliber M85 machine gun can be replaced by powder metallurgy steel forgings; 12 kinds of parts such as slide rule, bracket and bolt of 12.7mm caliber M2 machine gun can be replaced by powder metallurgy Replacement of metallurgical parts; 18 kinds of parts such as striker rod, ram-feeding rod, front and rear sights of the 7.62mm M60 machine gun can be replaced by powder metallurgy parts. For example, metal powder injection molding firearms launch iron, which is 4340 steel powder metallurgy parts. After heat treatment, the hardness reaches 38 to 42HRC (Rockwell hardness). After oxidation and blackening, it can replace the previous precision castings. The adjustable knob of the M16 rifle laser sighting system is also made of brass, steel and stainless steel powder metallurgy.
In terms of tank armored vehicles, the application of powder metallurgy parts is also more and more extensive. The American XM-1 tank engine gear adopts powder metallurgy parts, its performance is fully qualified, and the cost can be reduced by about 60%. In the differential gear of the M15lA2 military vehicle, the side gears, the axle gears and the paired gears are all powder metallurgy parts, which have good performance and reduce the cost by about 30%. The spur gears of the M60 tank drive train are made of 4620 steel powder metallurgy parts. Brake pump pistons of military vehicles, sintered iron powder metallurgy parts are superior in wear resistance and ablation resistance than previous aluminum products, which significantly improves product life.
In the application of artillery, Austria has used powder metallurgy technology to manufacture ablation-resistant nickel-based or cobalt-based alloys lined in the inner bore of the gun barrel to improve performance, with ablation resistance, wear resistance, wear resistance and other characteristics. The technology is relatively mature. The United States uses the hot isostatic pressing technology to manufacture the M113 type 175mm gun threaded breech block with complex shapes. Each piece can save 34kg (kg) of material, 15 man-hours, and reduce the quality by nearly 25%. In addition, the United States also uses vanadium-modified 4600 steel powder and natural graphite mixture to manufacture near-formed annular parts by powder forging methods for closed gas rings in large-caliber artillery tail assemblies.
2. The research and application of replacing traditional processes and materials has confirmed its feasibility
In addition to being used to manufacture some special weapon product parts (such as kinetic energy armor-piercing cores, artillery, projectiles and arrows anti-ablation lining, etc.), powder metallurgy technology can also replace traditional materials and processes for the manufacture of armored vehicles, firearms, and artillery. Or catapult parts to further improve performance and reduce costs. Many foreign studies or application examples have confirmed the feasibility in terms of performance, service life and cost, such as:
(1) 105mm howitzer cam
The size of the part is about 241mm × 152mm, the thickness is about 12.7mm, the height/thickness ratio of the reinforcing rib is greater than 10, and the thickness of the reinforcing rib is about 5mm. The cam groove has a complex configuration, and the allowable error is ±50μm (micron). U.S. Army research confirms the feasibility of powder metallurgy creep forging technology. They used 100-mesh 7075 aluminum powder, cold isostatic pressing under 276MPa (megapascal) pressure, sintered in nitrogen at 550 °C for 2 hours, and preheated the preform and forging die to 530 °C for isothermal creep forging. . The results show that the final mechanical properties meet the QQ-A-367H technical specifications, the tensile strength is greater than 490MPa, the yield strength is greater than 434MPa, and the elongation is greater than 3%. The comparative analysis of process cost shows that the cost can be saved by 30%.
(2) 151A2 Military Vehicle Differential Gear and Brake Pump Piston
The U.S. Army uses 4620 steel powder to manufacture differential side gears and bevel gears through powder metallurgy isothermal forging technology. The final material density can reach 99.5% theoretical density, tensile strength 876MPa, yield strength 630MPa, elongation 11.6%, section shrinkage 54.4 %, the impact value is equivalent to the performance of 4600 forged steel. These gears were installed on 7 M15lA2 cars for 35,000km (km) road and off-road sports car tests, and the results proved to be qualified. But gears made with this powder metallurgy isothermal forging technology cost 25% less. The use of sintered iron in the brake pump piston is to replace the aluminum piston and solve the corrosion problem. There is a small amount of tin-antimony-copper alloy powder in the sintered iron powder. After compacting and sintering, the hardness reaches 85-95HB, which is close to the standard aluminum piston. The porosity was 2%, and after immersing the polyoxyethylene glycol synthetic anti-corrosion lubricant, they loaded the sintered iron piston into the car and carried out a 20,000km assessment test. The comparison results showed that the aluminum piston was severely corroded and bonded, but the sintered iron piston Without any excessive wear or corrosion, it outperforms aluminum pistons.
(3) M60 tank spur gear
This spur gear is used in the M60 tank drive chain to match the main drive gear. TRW Corporation of the United States, with the support of the Army, believes that it is feasible to use powder metallurgy technology to manufacture such high-performance gears to replace forged steel parts. Using industrial water atomized 4620 steel powder, cold isostatic pressing under 414MPa pressure to make preforms, then sintering in 1200℃ hydrogen for 1 hour, and then performing precision isothermal forging at 900℃, 10t (ton)/square inch . The final material density can reach 99.5% of the theoretical density, and the mechanical properties are comparable to those of forged steel parts. The tensile strength is about 758MPa, the yield strength is about 580MPa, the elongation rate is 15%, and the area shrinkage rate is 40%.
(4) Navy 127mm guided shell tail
This kind of tail has extremely strict geometrical requirements. The total length is 198mm, the airfoil width is 58mm, and the thickness is about 9mm. The original design uses 17-4PH steel castings with a minimum strength of 1172MPa. The U.S. Naval Surface Weapons Center believes that powder metallurgy forging technology can be used. Manufacture this high-strength precision tail. They used 340g (gram) of 4640 steel powder, mixed with 0.48% graphite and 0.75% zinc stearate for compacting, sintered to reach 80%-85% theoretical density, and then preheated at 1200 °C for precision isothermal die forging immediately. After forging, the density can reach 99.5%~100% theoretical density, and the dimensional accuracy can reach ±2.5 μm. The mechanical properties can meet the design requirements, the tensile strength can reach 1207MPa, the yield strength can reach 1193MPa, the elongation rate is 5.3%, and the section shrinkage rate is 25.0 %, the material utilization rate reaches 83%.
(5) M567 fuze positioning bolt
The U.S. Army has confirmed that powder metallurgy can be used to make aluminum parts in artillery fuzes. Among them, the 60 and 81mm forced bomb fuze positioning bolts were originally designed with 2014-T6 aluminum billets, which were machined, and the tensile strength of the material was 400MPa. This part is manufactured by powder metallurgy technology. The material is industrial 201AB aluminum powder, and the composition is similar to 2014 aluminum. After the blank is formed by a multi-die press, it is sintered in a nitrogen atmosphere at 593 ° C for 30 minutes, and then the T4 or T6 state solid solution, Aging heat treatment, machine added to finished parts. The mechanical properties test shows that under the T4 heat treatment condition, the tensile strength exceeds 290MPa, the yield strength is 240MPa, and the elongation is 5%-6%. Dimensional analysis and density measurement results show that the final dimensional change is less than 0.3%, and the material density reaches 99% of the theoretical density. To prove its performance. An air cannon firing test was conducted to evaluate the post-launch structural integrity of the locator bolts installed in the M567 fuse, and the test results showed no damage or dimensional changes. The cost analysis shows that in the traditional cutting process, 60% of the material becomes cutting waste, while the loss of cutting material in powder metallurgy parts does not exceed 5%. Analysis shows that the total cost can be reduced by 25%.
(6) Powder metallurgy belt
In order to improve the performance of iron powder metallurgy elastic belt, the U.S. Army has studied the material properties of copper infiltration iron powder sintered elastic belt. The results show that copper infiltration can improve the strength of iron powder metallurgy elastic belt. For example, after the iron powder compact was sintered at 1120°C for 8 minutes, the tensile strength was 365MPa, the yield strength was 172MPa, the elongation was 21%, and the dimensional change was 0.006. After copper infiltration for 1 minute, the tensile strength increased to 372MPa, yielding The strength increased to 220MPa, the elongation decreased to 19%, and the dimensional change was 0.008.
(7) Powder metallurgy firearm parts
The US Army's 0.50 caliber M85 machine gun is a complex structure. Originally made of 4640 steel hammer forging and cutting process. In order to reduce costs, TRW Company made 400 powder metallurgy forging speed machines with 4640 pre-alloyed steel powder through powder metallurgy forging technology and handed them over to the army for assessment. After a lot of performance tests and room temperature and low temperature shooting assessments, the results are very satisfactory. Therefore, the Army has developed a military technical standard for powder metallurgy forging of 26 parts of the M-85 machine gun (MIL-F-45961). The comparative analysis results show that the strength and toughness of 4640 steel powder metallurgy parts are equivalent to those of forging steel parts, the hardness is 30-33HRC, the fatigue strength is 414MPa, the Charpy V-notch impact value at room temperature is 6.9kgf.m (kg. force meter), and the fiber The organization is fine tempered martensite. However, compared with the traditional process, the cost is reduced by 50%, the manufacturing process is reduced from 27 to 7, and the material utilization rate is increased from 17% to 90%