Ceramic moulds - to mass production
Accurate casting blanks for investment casting of reactive titanium alloys — very scarce competence. The specialists of Tactical Missiles Corporation were able to implement mass production of ceramic mould based on the domestic aqueous silicate binder. Such import substitution can effectively provide a new impulse to titanium casting in the Russian industry.
The CEO of the Corporation Boris Obnosov told to Intelligent Manufacturing Journal about peculiarities of modernization of production facilities and about future plans for diversification and increased presence in civilian markets. What is more, we got a unique opportunity to visit the shops of the head enterprise and see live the work of the new foundry line.
- Boris, could you tell us, please, what are the main advantages of the new foundry line?
The project of reconstruction and technical re-equipment of manufacturing from titanium alloys can be called unique. The technological process of obtaining titanium castings is very complex, and there are no more than a dozen enterprises capable of implementing it in our country. In addition, there is a serious personnel shortage in this direction: there are fewer and fewer specialists in the field of titanium casting. Despite the fact that the foundry is a major procurement base for later stages, today, many companies refuse foundries because of the high energy and material demand of the process, the hazards, unstable load of equipment cost. At the same time, the aircraft industry and other high-tech industries have a stable demand for cast products made of titanium alloys. As part of the technical re-equipment project, the titanium casting technology was completely re-equipped. Now modern robotic and automated equipment is involved in our foundry, new materials have been introduced. The influence of the human factor on the quality of products is minimized, while the culture of production has significantly increased. Casting stopped to be associated with constant dirt, dust, smoke. A wide range of existing casting technologies allows to obtain castings of any complexity with a wall thickness of 0.5 mm. One of the most common ways to obtain accurate casting blanks — casting on the smelted models. This technology is used in our production to produce castings from chemically active titanium alloys.
- So, what is the result?
The classical technology of investment casting is based on the use of environmentally harmful fire-hazardous materials based on organic ethyl silicate. With this method, the layer-by-layer formation of the ceramic shell is made by hand, and the uniformity of the layers is not provided. The use of an aqueous binder based on colloidal silica, until recently, been limited by the instability of the properties of ceramic molds and the risk of alteromonas gas-saturated layer on the surface of the resulting titanium castings. Such products have a specific surface color and have increased fragility. However, our engineers managed to neutralize this problem. The parent company was one of the first in Russia to introduce serial production of ceramic moulds based on domestic aqueous silicate binders. The new production line and new technology allowed to increase the production capacity of the titanium casting shop from 10 to 25 tons of suitable casting per year and significantly reduce the percentage of defects. The modernized line allowed to improve the quality of production processes, as well as to create a center of technological competence of titanium casting, in the interests of not only KTRV enterprises, but also defense industry. Currently, the line is loaded by 25%, applications have been sent to many Russian enterprises. We are ready to produce cast products for outsourcing to defense and civilian enterprises. The creation of the competence center for titanium casting in Korolev can be considered a prerequisite for the emergence of such technology centers different profile orientation at our other enterprises. For example, Perm plant "Mashinostroitel" has serious competencies in electron beam welding.
- What type of equipment is used in foundry shop now?
The complex of the equipment introduced under the project "Reconstruction and technical re-equipment titanium alloys products manufacturing" allows to minimize manual labor. Previously, the application of refractory slurry to the model blocks and the movement of ceramic moulds was carried out manually, now it is done by a robot as part of a robotic line. This is important, given the fact, that many ceramic moulds at the final stages of the manufacturing process weigh more than 35 kg. In the course of modernization in the foundry were installed: injection moulding the injection machine for the manufacture of wax models, layer-by-layer robotic system producing ceramic molds for investment casting, boilerclave to remove wax model compounds, shaft furnace for loss on ignition of moulds and vacuum arc melting and casting plant for melting and mould filling of titanium alloy. The main difficulty associated with the introduction of this equipment was that it was initially operated with the use of imported materials exclusively, the supply of which ceased on 1 February 2018 due to a new package of sanctions. In many ways, this fact prompted us to search for domestic substitutes. The Russian company Vakuumtekh was able to develop and produce aqueous binders. To adapt domestic materials, the robot was reprogrammed, a microclimate control system was installed in the production premises of the shop, the composition of the suspension and the modes of its application to the model blocks were changed. In March of this year, the line was launched, and the first results of its work showed that the suspension, prepared on domestic materials, has better technological and rheological properties compared to imported analogues. Huge research work created a basis for the modernization of production lines at other plants was done, because Vakuumtekh, became the first domestic manufacturer of such materials for casting on investment casting.
- How much time and money did it take for such a large-scale project?
Modernization of the foundry began in 2013 and was completed in March 2019. The total cost of the project amounted to more than 800 million rubles.
- Investment casting technology assumes the presence of moulds in the production process. Usage of this kind of equipment is justified in large-scale production. But when it comes to small nomenclature, exclusive production, the production of moulds will significantly affect the cost of production. Additive technologies allow to solve this problem by creating exclusive moulds or even ready-made master models. Do you plan to include 3D printers in your investment casting line?
We are planning to use 3D printers in the production of burnable models and reusable model tooling. In accordance with the program of development of additive technologies, a number of experimental works are carried out in the Corporation, as a result, the composition of additive equipment will be determined taking into account the specifics of our products. With the help of 3D printers, we will be able to quickly prepare the foundry for the development of a new nomenclature or produce small series of castings without tooling, which meets the requirements of the market.
It should also be noted that in terms of technological preparation of production, we do not stand still. In conjunction with Moscow Aviation Institute conducted a research entitled "Design of Gating-feeding systems and modes of centrifugal casting of shaped castings of titanium alloys", the result of which is the software for calculating the parameters of the Gating-feeding system that ensures smooth filling with melt and meal the massive knots of the casting. This SOFTWARE, the right holder of which is JSC "KTRV", will allow us to ensure the quality of castings at the stage of technology development and reduce the time of its development.
- The renewal of the foundry also opens up new opportunities for KTRV in terms of diversification also. How do you, personally, assess the overall readiness of the Corporation to expand the production of civilian and dual-use products?
Without any doubt, our main profile is weapons. Nevertheless, we have experience in creating civilian products from scratch. Idea, research work, development activity, serial production — the algorithm is established, it remains only to choose the demanded industrial product. KTRV created a special structure for the production of civilian and dual-use products, it is actively developing and looking for potential customers. The President of Russia has set a goal to increase the share of civilian production by 2025 to 30%, and by 2030 to 50%. It is a difficult task, but there is support for the process of diversification of production, including from the Ministry of Industry and Trade. Available production facilities and scientific potential allow to produce almost any high-tech products. And today we are already producing competitive civil and dual-use goods. For example, our altimeters are among the best in the world, our avionics and engines are used in the production of small aircraft. We produce propulsion systems for emergency rescue crews of spacecraft in case of accident space rocket complexes at the start and in flight, the engines of soft landing and low-thrust manned spaceships, solid-fuel gas generators used in missile and aviation equipment, mobile fire fighting systems, light multi-purpose aircraft. In addition, the Corporation's enterprises produce safety systems for gas equipment, portable boilers and domestic gas boilers, equipment for nuclear power plants, medical equipment, including for the treatment of cancer, mobile medical laboratories for express diagnostics, communication and diagnostic systems for railway transport and engineering.
- Large corporations are often criticized for the inefficiency of production processes, for downtime of expensive equipment. Has this experience been taken into account? Why the foundry shop was chosen as the technical re-equipment object?
We prepared for the modernization of the foundry very carefully. For reconstruction, the weakest production link was chosen for a number of reasons. Harm, negatively affecting human health and the environment, outdated mentally and physically equipment, significant costs of materials, a sensitive percentage of spoilage. According to Deputy Director General Chief Engineer of KTRV Vladislav Roditelev, now the foundry has changed beyond recognition:
According to the old technology, the moulds were made on the basis of ethyl silicate-an organic material, in the preparation of which ethyl alcohol and ammonia are used. The cabinets where the moulds were drying were not airtight, so the smell of ammonia spread throughout the shop. The production resembled a children's sandbox, around which sand is always scattered. But unlike sand, hydrolyzed ethyl silicate is subject to chemical hardening, after which it can only be removed with a pneumatic hammer.
Smooth clean floors, air conditioning, no unpleasant smells. The shop casting of titanium alloys manufactures different casting blocks for mass production. The production cycle begins with the preparation of a metal mould, which is then installed in the injection moulding machine. Molten wax is pressed into the tooling, after solidification of which the model is ready for the next stage — layer-by-layer application of ceramic composition. It was on this site and focuses on the major innovations — the robotic system, automatic conveyor and tanks with a ceramic slurry and thereby domestic binder. The wax model is assembled into a block and mounted on a special support, the robot captures it and lowers into a container with a suspension. Next, the block is sprinkled with fine-grained electrocorundum and dried on a conveyor. The operation is repeated until the required number of layers of ceramic suspension is applied, depending on the technological requirements and the size of the wax model. Climate control systems maintain a constant temperature and humidity on the site. It takes 36 hours — and the first batch of moulds is ready. Then every 24 hours it is possible to remove from the conveyor up to 42 finished ceramic moulds.
— Russian material, and it is not only a binder but also electrocorundum, cheaper than the imported counterparts by more than four times, — says Vladislav Roditelev. If earlier in these banks "revolved" about 3.5 million rubles, now-800 thousand. Significantly reduced and material consumption, now the suspension is distributed on the model blocks more evenly, without stains, the shell has a wall of the same thickness. The properties of the binder allow to drain the excess volume of ceramic suspension before the operation of dusting, and special additives provide high-quality coating of wax models.
Talking about lean manufacturing, the positive effect of the introduction of automation, many experts prefer to rely on real production experience. The foundry line in Korolev is a very convincing example in this respect. Robotic cell of the KTRV`s foundry complex greatly facilitated the work of personnel and virtually eliminated the role of the human factor in such critical operations as the application of ceramic slurry and layer-by-layer drying. In the future, the new line can become the Foundation for further automation and digital transformation of the enterprise.
Vladislav Roditelev showed us melting area where they get wax moulds from ceramic forms. Boilerclave heats the water to 180 degrees Celsius, thereby turning it into superheated steam. For complete melting of the wax from the ceramic model requires 10 minutes of exposure at a pressure of 8 technical atmospheres. Still fragile at this stage, the ceramic mould withstands the process of melting without cracking. Pressurized steam, as it penetrates through the ceramic crust and instantly transmits the heat of the wax model, not allowing it to expand. According to the old technology, the wax would be melted out of the mould in hot water for about 30 minutes.
After a boilerclave the ceramic mould allows to settle in the shop`s atmosphere about 12 hours and then it can be ignited in the furnace about 900 degrees Celsius.
Final stage – filling of titanium in ceramic moulds. Because of physicochemical properties of titanium alloy, and this metal in liquid state in interaction with the oxygen which is contained in air becomes explosive, process happens in the vacuum environment. On a centrifugal table of the vacuum melting and pouring equipment the container with the ceramic mould fixed on a special strut where the melted titanium will be filled in is established. The water-cooled melting crucible in which the crust from titanium alloy called by a skull is constantly supported is installed in the camera of the furnace. Melting is conducted by melting of a titanic electrode with a diameter of 360 mm.
The process resembles arc welding, - says the chief metallurgist Ilia Kontorovich. - The electrode descends down the crucible, the electric arc is ignited with current intensity up to 40,000 amperes and melting begins. When the electrode is completely melted, operators bring the metal to a certain temperature, turn on the rotation of the centrifugal table, and pour the alloy into the molds through the metal riser. After cooling, the riser container, which may be at the same time up to eight molds, is removed from the furnace, castings are cut off from the runner system, ceramics are cut off and titanium articles are sent to the finishing section.
Thanks to the modernization of foundry and the introduction of new technology, the productivity of the workshop is up to 25 tons of suitable casting per year, and the percentage of scrap of ceramic moulds and finished titanium products is not more than 5%. The entire production cycle, starting with the wax melted model and ending with the finished casting, takes ten shifts. The high performance of the robotic line will allow KTRV to fulfill third-party orders, which is important given the needs of Russian enterprises in titanium casting.