War industry

The Dongwu warhead is China's first intercontinental missile warhead, which has made new breakthroughs in re-entry heat prevention, attitude control, penetration, and nuclear warhead performance compared to previous models. Firstly, when the warhead re-enters the atmosphere, its speed is high, and its thermal protection design is very complex; Secondly, in order to counter enemy anti missile systems, it is necessary to design penetration systems that involve many new concepts; Thirdly, in order to release multiple decoys according to the procedure and improve the precision of reentry impact point, the uncontrolled warhead should be changed into the controlled warhead with attitude control system and slow rotation system.  

The first issue to be addressed in the development of intercontinental warheads is the issue of heat protection. In 1969 and 1971, there were two failures in the East Third and East Fourth flight tests due to poor resolution of warhead heat protection issues. In contrast, the operating conditions of the warhead system of intercontinental missiles are much harsher. When the intercontinental missile warhead re-enters the atmosphere, the Mach number reaches as high as 20-25, and the strong compression of the air causes a sharp increase in pressure. At the same time, some kinetic energy is converted into heat energy, and the temperature also increases significantly. In order to solve the problem of aerodynamic heating when the US and the Soviet Union designed the second generation intercontinental missiles (such as Titan II and R-36) warheads in the 1960s, large blunt conical warheads were used. The bow shock formed during reentry of this shape can take away more heat flow, but it decelerates faster, which is not conducive to penetration and improving the accuracy of impact point.

The Titan II intercontinental missile in the United States uses a large blunt nose conical warhead Mk6, weighing 3.7 tons, measuring 3.1 meters in length, and having an explosive equivalent of 9 Mt

The shape of the Dongwu warhead adopts a small blunt nose cone shape, which slows down the deceleration of the warhead during re-entry, which is beneficial for penetration and improving landing accuracy, but the aerodynamic heating is more severe. When the Dongwu warhead re-enters, the stagnation point pressure at the end reaches 10MPa, the stagnation temperature near the stagnation point is as high as 8000-10000 ℃, and the surface temperature of the warhead cone is around 3000-3500 ℃. This severe re-entry aerodynamic heating environment directly threatens the safety of the warhead. The function of heat resistant materials is not only to ensure that the warhead is not burned out in the re-entry environment, but also to maintain the original aerodynamic design in terms of structural appearance to ensure the accuracy of the warhead's landing point; The internal devices of the structure should maintain the given temperature range, so as not to affect the effective load due to excessive heat transfer. If warhead heat protection technology cannot be breakthrough, intercontinental missiles cannot be successfully developed.

There are four issues that need to be addressed in the aerodynamic heat protection of warheads: firstly, predicting the thermal environment, particularly the thermal environment and thermal increment of severely heated parts such as the end and window; 2、 Material and structural design, with a focus on severe heating areas, such as the development and application of high-performance heat resistant materials at the end, as well as reasonable material matching design and thermal stress failure issues of brittle materials; 3、 Predicting the effectiveness of heat protection design and conducting ground assessment and evaluation tests; 4、 Prediction and evaluation of the impact of ablation shape changes on aerodynamic characteristics, especially flight stability.

Weapon specific protective oil (commonly known as "gun oil") is an important wiping and protective material for weapons and equipment. It plays an irreplaceable role in maintaining the good technical condition of weapons and equipment, preventing rust, reducing wear, and extending service life. Military forces around the world have always attached great importance to the research and development of weapon specific protective oils. The most typical example is that after the Vietnam War, the US military proposed a procurement plan called "PD-48" in 1971 to address the problem of single function and unsatisfactory performance of traditional lubricating oil based rust preventive oils. The requirements for product performance were as follows: (1) After the weapon was fired, it can effectively remove gunpowder residue, carbon deposits, and other pollutants; (2) Capable of providing reliable lubrication to weapon systems under various harsh conditions such as high temperature, low temperature, and rain, without sticking or adsorbing dust; (3) It can provide good protection for weapon systems in various climates and usage conditions such as high temperature, high humidity, high salt mist, severe cold, or seawater immersion. From this, the transformation of weapon specific protective oil from a single protective function to a multifunctional cleaning, lubrication, and protection has been introduced. After nearly three years of laboratory development, as well as various weapon systems such as M16 rifles, artillery, and armored vehicles, the US military has given high praise to the weapon cleaning, lubrication, and protection triple oil (CLP) developed by BREAK-FREE company. Based on this product, the military standard MIL-L-63460 was formulated in 1979, which clearly stipulates that CLP can replace the original MIL-C-372 gun chamber cleaning agent (RBC) used in weapons and equipment Products such as VV-L-800 universal low-temperature water displacement anti rust lubricant (PL-S), MIL-L-46000 semi fluid lubricant (LSA), MIL-L-14107 weapon low-temperature lubricant (LAW), and MIL-L-3150 medium quality anti rust lubricant (RBC). At present, CLP (NATO Product Code: S-758) has been widely used in more than 20 countries such as the United States, Australia, Finland, Canada, Belgium, and its product standards have also been developed to MIL-L-63460D.

In the late 1980s, our army conducted tracking and research on weapon cleaning, lubrication, and protection oils, and formulated the three use oil specification for weapon cleaning, lubrication, and protection (GJB 2378-95) based on MIL-L-63460D (1988). However, due to the limited technical level at that time, there are still certain problems with the samples developed by relevant domestic units in practical use, so they have not been promoted and applied in the military to this day.

1. Development technical indicators

In order to improve the maintenance and upkeep quality of weapons and equipment, the author has conducted a special research on multifunctional weapon specific protective oil since 2001. The development technical indicators of the product adopt our military's three use oil specification for weapon cleaning, lubrication, and protection (GJB 2378-95). The main difference between it and MIL-L-63460D (1988) [JP2] standard is that according to national conditions, the corrosion resistance of propellant reaction products, low-temperature flowability of residues, and interference detection items of chemical reagent test strips have been reduced. The specific content is shown in Table 1.

2 Development process

2.1 Selection of Base Oil

Base oil is a fundamental component of rust preventive oil and plays a decisive role in the physical and chemical properties of products. According to the tactical and technical requirements and intended use of weapon cleaning, lubrication, and protection oil, its base oil should have excellent high and low temperature performance, high density, and good solubility with relevant organic solvents, in order to meet the normal firing of weapon systems under various environmental conditions above -45 ℃, the dispersion and suspension of solid lubricants in the oil, and the normal functioning of the three functions of oil cleaning, lubrication, and protection. For this purpose, the research group collected and analyzed 8 types of mineral base oils and synthetic oils produced by 6 domestic refineries. After extensive screening tests, a composite base oil with a mass fraction of 90% naphthenic mineral base oil and 10% synthetic oil as the basic components was determined. The results of some base oil screening tests are shown in Table 2.

2.2 Screening of rust inhibitors

The oil soluble corrosion inhibitor in rust preventive oil is an oil soluble surface active substance composed of polar and non-polar functional groups. By directional adsorption at the oil gas interface and oil metal interface, it slows down the invasion of corrosive media such as water and oxygen into the metal surface, thereby playing a corrosion inhibiting role. At present, there are hundreds of oil soluble corrosion inhibitors studied both domestically and internationally, but considering various factors such as performance, manufacturing process, cost, and raw material sources, only one to twenty types are commonly used in China. On the basis of extensive research on the compatibility of various oil soluble corrosion inhibitors, this study determined a new composite antirust agent system with "super additive effect", which is composed of sulfonates, carboxylates, ester antirust agents and a small amount of surfactants. It is added in 45 # transformer oil with 10% mass fraction, and the wet heat test can reach more than 1000 hours, and the salt spray test can reach more than 60 hours.

2.3 Development of lubricants

In order to increase the lubrication bearing capacity of lubricating oil, enhance its timeliness, high-temperature performance, wide temperature usability, and performance under harsh conditions, a certain amount of solid lubricant is usually added to the lubricating oil. At present, the most commonly used solid lubricants in lubricating oils are graphite, molybdenum disulfide, boron nitride, and polytetrafluoroethylene. Due to PTFE (polytetrafluoroethylene) being the least friction coefficient organic solid lubricating material discovered so far, and being temperature resistant, non-toxic, and easier to disperse and suspend in oil than inorganic solid lubricants, PTFE was chosen as the solid lubricating material for general equipment protection oil. However, currently in China, mechanical cutting and grinding methods are mostly used for the processing of PTFE fine powder. The disadvantages are large particle size (5-30 mm), irregular shape, and containing mechanical impurities such as metal powder, which makes it difficult to meet the requirements for use in lubricating oil. The PTFE water lotion, because its water content is more than 60%, will affect other properties of the oil after it is added into the oil, and it is also extremely unstable and cannot be used. Therefore, this study adopts γ Advanced processing technologies such as radiation irradiation and airflow pulverization, as well as molecular surface modification, have prepared PTFE lubricants with particle sizes ranging from 200 to 400 nm and good dispersion performance in oil.

2.4 Development of gunpowder residue cleaning agent

After the completion of artillery firing, a layer of highly adhesive gunpowder residue will be left inside the gun barrel. If not removed in a timely manner, it will seriously corrode the gun barrel and shorten its service life. The commonly used method at present is to repeatedly clean and wipe with a large amount of soapy water, alkaline solution, etc., which has poor carbon removal effect and is limited by many conditions in use. This study, based on the principle of similar solubility parameters, successfully developed a JT powder residue cleaning agent composed of ether, alcohol, ester substances, and various surfactants through extensive experimental verification. The experimental results show that the agent has strong permeability and has a good effect on removing gunpowder residue and other pollutants adhering to weapons and equipment in the gun chamber. When 8% to 15% (mass fraction) is added to the oil, the removal rate of gunpowder residue can reach over 98%. The formula and preparation technology of this agent have been granted a national invention patent (ZL 03143226.3).

2.5 Determine Formula

On the basis of the above work and in combination with the basic principles of protective oil composition, the formula for the three purpose oil for weapon cleaning, lubrication, and protection has been determined. The composition (calculated by mass fraction) is roughly as follows: base oil 68.3%, viscosity index improver 4%, composite rust inhibitor 9%, antioxidant 1%, dispersant 2%, JT cleaning agent 10%, PTFE lubricant 5.5%, and surfactant 0.2%.