Ultra-High-Strength Steel Cold Stamping (UHSS)
Technology 01
In order to realize the weight reduction of a vehicle body, it is essential to reduce the weight of the skeleton constituting the body parts. As a method for reducing the weight of the skeleton, we use 1,180 MPa-grade and 1,470 MPa-grade ultra-high strength steel called the UHSS materials. The UHSS materials are used for, for example, the reinforcement of the center pillar, and also used for important pars such as the rocker outer passing under the doors, and the floor cross extending in left and right directions under the seats, as the countermeasures against safety problems at the time of side collisions and offset collisions, and the ride quality such as the twisting of a vehicle body and abnormal sound during running.
Difficulties in cold stamping of ultra-high-strength steel
Advantages of Using UHSS Materials
The UHSS materials (ultra-high tensile steel plate) have many advantages when used for automobile parts. At first, since the UHSS materials are lightweight while having high tensile strength, it becomes possible to realize the weight reduction of a vehicle body to contribute to the improvement of fuel efficiency and the reduction of CO2 emissions. In addition, since the strength is high, the shock absorbance performance at the time of collisions is improved to lead to the safety enhancement. Further, since thin-walling is possible, the degree of freedom in design increases, and it becomes possible to manufacture parts having complex shapes and to reduce the number of parts to contribute to the improvement of assembly efficiency and the cost reduction. With these characteristics, the UHSS materials are essential for realizing the next generation automobiles having excellent environmental performance and safety performance.
Images of effective strengths at the same cross section (outer shape)
The high-strength materials can ensure the same bearing force (strength) even in the case of having the same outer shape and a thinner necessary plate thickness, and it is advantageous for weight reduction (see the conceptional images).
The outer shapes are the same, and each of the above images is a conceptual image illustrating a necessary plate thickness for ensuring the same bearing force (a guide for maintaining the bearing force).The rigidity (for deflection and twisting) is separately ensured by cross-sectional design.
Our Strengths
For ultra-high-tensile (UHT) steel, which is particularly challenging to press-form, we work closely with our customers from the development stage onward. Using CAE analysis and prototype dies, we refine our simulations based on actual measurement data to develop part geometries and forming methods that enable high-precision forming. This allows us to begin production preparation at an early stage for manufacturable UHT steel stamped parts and to establish processes that consistently produce high-quality parts.
Hot Stamping
Technology 02
Hot stamping technology involves heating material specifically designed for hot stamping to approximately 900°C, press-forming it while soft, and simultaneously quench-hardening it in the die. This process enables the production of high-strength, lightweight parts in the 1.5 GPa to 2 GPa class. Another major advantage is that even complex shapes that are difficult to achieve with conventional cold pressing can be formed with high dimensional accuracy.
Strengths of Toyotetsu's Hot Stamping
The Toyotetsu's hot stamped parts are used for reinforces of the center body pillars from the 2003 model PRIUS and are the advanced technologies globally used for production in the United States, Turkey and China. In addition, Toyotetsu employs the direct water-cooling system (a system of making cooling water to directly flow on the metal surface) for cooling molds. With this, the mold temperature is kept low to realize high productivity.
Toyototsu
Technology 03
"Toyototsu" is the technology of realizing soft and comfortable touch feelings at portions in contact with human bodies such as automobile interior parts at low cost. By changing the layouts and angles of fine convex shapes, desired touch feelings (favorable touch feelings) can be freely realized.
What is Toyototsu?
Our original technology "Toyototsu" is the technology of imparting fine convex shapes to the back surface of the injection molded skin made of elastomer resins to express softness. Since it can be assembled without using adhesives, it can be easily disassembled and recycled. So, it is the eco-friendly technology. Toyototsu is employed for armrests, console boxes and instrument panels of automobiles.
Related Products
Joy of Toyototsu
The structure of the conventional door armrest has 5 layers, and the touch feeling is expressed using the foam layer made of urethane. On the other hand, the Toyototsu part is constituted of 2 layers only, that is, the molded product and the base material, as shown in the upper right figure, and a touch feeling is expressed using fine convex shapes. Although the number of the manufacturing processes of the conventional product is 10 such as lamination of urethane, cutting of skin, sewing, application of adhesives, and drying, with this structure, the number of the manufacturing processes of the Toyototsu part is reduced to 3 processes only, that is, surface layer injection molding, base material injection molding, and assembly. So, it realizes the cost reduction. In addition, as compared to the conventional product, the Toyotetsu product is free from disposal of cutting scraps, and adhesives. Thus, the surface layer and the base material can be separated even after assembly, and the Toyototsu product can be fully recycled. Thus, it has the eco-friendly structure.
Toyototsu's Technology
It controls the inclination direction of Toyototsu and lays out "convex" portions so that the "convex" portions do not interfere with each other. With this, a natural touch feeling is expressed.
A desired touch feeling with no feeling of bottoming out is expressed by combining a material and a shape, and it is capable of controlling the touch feeling according to the used portion.
LSW（Laser Screw Welding)
Technology 04
The laser screw welding (LSW) has high productivity due to a long focal length laser using a Galvanometer mirror and is attracting a lot of attention as the future alternative technology to spot welding. We have succeeded in mass production of bumper reinforces and are increasing the number of applied products.
Advantages of LSW
The welding time is from one-fifth to one-fourth as compared to that of spot welding, so LSW has high productivity. In addition, it can ensure high welding quality also in lap welding of galvanized steel plates.
Laser Cutting
Technology 05
The laser processing is a processing method of performing cutting by applying the laser light to the product to melt the irradiated portion and removing the melted metal portions by high pressure air. Since the high energy of laser is efficiently used, it is possible to perform high-speed cutting. Also, since the laser light is very thin, it is possible to perform precise processing.
Advantages of Laser Processing
The hot stamped product has high strength after hardening. So, in order to perform drilling or trimming of complex three-dimensional shapes, we use laser processing. We have introduced laser processing machines to make it possible to perform precise cutting processing. Thus, we realize the enhancement of the product strength.
Material bonding
Technology 06
The material bonding is the technology to bond steel plates having different plate thicknesses and/or made of different materials. With this, we can realize the weight reduction and cost reduction while focusing the part strength and rigidity on necessary portions. We have 5 bonding technologies, that is, mash seam welding, laser welding, plasma welding, laser arc hybrid welding, and laser filler welding. We can perform processing using an optimum method according to the number of production, shapes and materials. In recent years, due to the increase of thin plate materials and the needs for high strength, the use of laser arc hybrid welding and laser filler welding has been increasing.
What are Laser Filler Welding and Laser Arc Hybrid Welding?
The laser filler welding is the technology making it possible to stably perform welding at high quality even in case of bonding members having a plate thickness difference or a gap, or high strength steel by combining laser having high energy density and a filler material.
The laser arc hybrid welding realizes both deep penetration and high-speed welding by making the laser and the arc to work at the same time. With this, it is suitable for welding thick plates. The both technologies are the advanced bonding technologies suitable for materials having different thicknesses and high strength steel.
Advantages of Laser Filler Welding and Laser Arc Hybrid Welding
The laser filler welding surely fills the thickness difference and gaps by precise filler supply control and realizes the high strength and the beautiful bead appearance while preventing underfill. The laser arc hybrid welding is capable of performing high-speed and stable welding with the deep penetration of lasers and the excellent filling property of arc. The both technologies realize tailor welded blank at high quality and with high reliability, and significantly contribute to the weight reduction and performance improvement of automobile parts.
Thin Plate Plasma Weld
Technology 07
The thin plate plasma welding is the method of melting and bonding metallic materials using high-temperature and high-energy plasma arcs occurring between electrodes and the base material while protecting the melting portion by plasma gas and shielding gas.It can be applied even to thin plates, and it is possible to perform highly accurate and stable welding.
Advantages of Thin Plate Plasma Welding
Since the sputters are little and the bead appearance is very beautiful, the thin plate plasma welding is optimal for automobile parts requiring the appearance quality. In particular, we produce lightweight brake pedals having a hollow structure using this plasma welding technology to significantly contribute to the weight reduction and performance improvement of vehicle bodies.
FSW（Friction Stir Welding）
Technology 08
The friction stir welding (FSW) is the bonding method in which the rotation tool is pushed into the bonding portion and stirring materials softened by friction heat and processing heat to realize bonding, which is suitable for aluminum press parts. Due to the employment of aluminum parts based on the needs for weight reduction of vehicles, the use of FSW is expanded as an alternative to conventional spot welding and arc welding. The FSW is expected to use not only for the bonding of aluminum materials but also for the bonding of different materials such as "aluminum and iron" and "aluminum and resin" in the future.
FSWとは
FSWのメリット
- Since the FSW is the bonding method not melting materials, the distortion and the deformation amount are small as compared to fusion welding.
- The metal structure of the joint portions obtained by using the FSW becomes the fine crystal structure and has higher bonding strength than that of the metal structure obtained by using fusion welding such as MIG.
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The welding process is simple and the management thereof is easy.
- The boding tool is just mechanically rotated and moved.
- Flux-cored wire and shielding gas are not required.
- No sputters and fumes
- Power saving -> One-third of conventional welding
- It is possible to perform bonding of aluminum castings which is said to be difficult, and it is also possible to reform.
