What is the point of distortion-free aluminum heat treatment? Learn from Kwangyang Sangyo, an expert in metal heat treatment
In recent years, aluminum has attracted attention for its functions obtained through heat treatment. When aluminum is heat-treated, its hardness and tenacity increase and its durability improves, achieving both lightness and strength. On the other hand, it is said that there is a trade-off relationship between hardness and distortion, as the hardness and distortion tend to occur more easily. Rapid cooling at a low temperature in pursuit of hardness increases distortion even if strength is high, which is the difficult part of heat treatment for aluminum. This time, we interviewed Koyo Sangyo Co., Ltd., located in Kasaoka City, Okayama Prefecture, whose main business is manufacturing small steel products and metal heat treatment, about the functions obtained from aluminum heat treatment and points to be aware of.
In recent years, attention has been paid to the functions obtained by heat treatment of aluminum, and inquiries about heat treatment of aluminum are increasing. What specific functions can be obtained, and what points should be paid attention to in heat treatment? We interviewed Mr. Takashi Yokoyama, a key person in Koyo Sangyo who is an expert in metal heat treatment, who is attached to the president, Mr. Shingo Nawawaka, who is the manager of the heat refining department, and Mr. Tomohiko Sagawa, who is the deputy manager of the heat refining department.
Koyo Sangyo performs comprehensive heat treatment with high precision and ultra-short delivery
Koyo Sangyo Co., Ltd., headquartered in Kasaoka City, Okayama Prefecture, has a small steel manufacturing department, objects and processing methods. consists of a wide variety of metal heat treatment divisions. The strength of the heat treatment department that we will be discussing this time is "high precision and ultra-quick delivery even in small lots". This is the result of accumulating technical know-how and continuing to invest in various types of equipment for heat treatment in general.
We maximize the characteristics and performance of various facilities that can meet various needs, and reliably perform heat treatment of the required quality. We have also advanced automation and established an ultra-short delivery system.
Heat treatment methods and equipment require expertise. All staff members of the company are qualified as heat treatment technicians, and by acquiring expertise in accordance with various facilities, they are able to respond to a wide range of customer requests.
Appropriate inspections are carried out according to the steel type and heat treatment, such as hardness inspections, structural inspections, and detailed component analysis. We have earned a high reputation, such as obtaining ISO9001 and JIS G 3101 (rolled steel for general structural use SS400) for the first time in the wrought iron industry, as well as being certified by major manufacturers.
The inspection management of thermometers and hardness gauges and the management of equipment are thorough, and it is possible to present the evidence of the temperature and environment in which the heat treatment was performed.
What functions can be obtained from heat treatment of aluminum
In recent years, there has been an increase in inquiries about heat treatment of aluminum, but why is that in the first place? “For example, in the automobile industry, vehicles are becoming lighter. If we can reduce the energy consumption of vehicles by improving fuel efficiency, we can expect to reduce greenhouse gases. Although it tends to increase, weight reduction is also required in consideration of fuel efficiency and the needs of the world at the same time.Therefore, the introduction of weight reduction technology is accelerating, and aluminum, a non-ferrous metal, which is a light material, is also attracting attention. Appropriate heat treatment is essential to increase the strength and reduce the thickness of aluminum.” (Mr. Sagawa)
When aluminum is heat-treated, its hardness and tenacity increase and its durability improves, achieving both lightness and strength. On the other hand, it also has the characteristic that distortion is more likely to occur as hardness is sought. Hardness and strain are in a trade-off relationship. "If you seek hardness and quench at a low temperature, the distortion will increase even if the strength is high. This is the difficult part of heat treatment of aluminum."
Also, in the course of the company's aluminum heat treatment, there is a case where the customer himself was able to give benefits that he had not imagined. It is said that "heat treatment can remove the residual stress hidden in aluminum and greatly reduce the number of man-hours for aluminum processing." “The aluminum parts, which are the raw materials for aluminum parts, generally have residual stress, such as peculiarities and wrinkles, that occur during manufacturing. If the aluminum parts warp due to residual stress, the cutting process to make the parts will be difficult. However, if the residual stress in the aluminum member is removed, it will be easier to process, for example, processing that used to take 3 hours can be done in 1 hour, and precision can be improved in micron units. Therefore, even customers who know this fact appreciate the heat treatment of aluminum.” (Mr. Sagawa) “Aluminum is originally a material that is easy to cut. It's hard to notice the need for heat treatment because it's stored away.However, the amount of processing man-hours, time, and costs that can be reduced by heat treatment is considerable when considered in total."
Cooling after heat treatment is the key to suppressing aluminum distortion and pursuing thinness
"Technological development for non-ferrous metals is one of our important themes." At Koyo Sangyo, in order to meet the growing needs for aluminum parts, we have been focusing on capital investment for many years, not to mention improving our technical capabilities and accumulating know-how. “In order to meet the growing demand for aluminum such as die-cast and cast products, we have introduced a dedicated 800kg-class furnace for solution treatment. In addition, we have also developed our own cooling equipment that allows us to flexibly set the cooling temperature so that we can respond to customer requests for strength and accuracy in detail.The level of heat treatment quality and traceability that is difficult to achieve with in-house production. can be provided.” (Mr. Yokoyama)
The company teamed up with a boiler manufacturer in 2019 and developed a water cooling system that can control the water temperature from room temperature to 95°C. “When cooling with water at normal temperature, the strength is very high, but the distortion is also large. It is possible to pursue thinness at the same time, while keeping the product within the required length.” (Mr. Nawawaka) “We have introduced a heating furnace that can process even tall products, and water cooling water tanks can be adjusted according to the amount of products. The temperature can be controlled at a constant level, and even if the lot is small, we can propose the optimum heat treatment, so we can contribute to the prototyping of aluminum parts for commercialization." (Mr. Sagawa)
For customers who say, "I don't want distortion as much as possible, even if it means sacrificing hardness," we developed an air cooling system in the spring of 2021 that can reduce distortion to within 1mm. “By changing the cooling method after solution treatment from water cooling to air cooling, which is forced air blowing, it is possible to suppress distortion as much as possible. Therefore, we recommend air-cooling for customers who don't mind if the hardness is not enough, or if distortion is a problem.” (Mr. Nawawaka) There is an overwhelming increase in the number of customers who are demanding .The higher the accuracy, the easier it is to assemble.For this reason, 80% of customers who previously requested water cooling are now requesting air cooling." (Mr. Sagawa)
Strong in heat treatment for materials other than aluminum
Koyo Sangyo is capable of comprehensive heat treatment. We will also introduce some of the heat treatment other than aluminum, along with the company's strengths.
When stainless steel is heat treated in air, a large batch furnace with a width of 1200 cm, a length of 2000 cm, and a height of 600 cm is used. Large stainless steel castings can also be treated with solutions, etc.
By heating in a vacuum state and cooling with an inert gas, it is finished cleanly without the adhesion of oxide scale. When stainless steel is heat-treated in a vacuum, it is possible to minimize distortion during cooling by heating it to 1000°C or higher and then cooling it with nitrogen. In the heat treatment of stainless steel, it can be used properly based on the customer's needs, such as heat treatment in the air for post-processing and vacuum heat treatment for finished products.
The company has a line configuration that can automatically operate the nitriding process. By registering pre-processed products in the three-dimensional warehouse, it becomes possible to automatically perform everything from pre-cleaning to nitriding and post-cleaning, making it possible to achieve short delivery times. Metal heat treatment, such as wanting aluminum parts with both strength and precision, wanting to reduce the man-hours and costs required for aluminum cutting, wanting to make prototypes with steel materials for commercialization, albeit in small quantities, and wanting to ensure traceability in heat treatment. If you have any troubles or orders regarding this, please contact Koyo Sangyo first.