in Vol. 15 - May Issue - Year 2014
With Both Traditional and Leading-edge Technologies, market for Surface Finishing will be Greatly Expanded
Hiroshi SHIMIZU, Assistant GM of Special Products Division of Itoh Kikoh Co., Ltd.
Fig. 1: the grain size and hardness corresponding
Fig. 2: Gas Atomizing method
Fig. 3: the lifetime of stainless beads and glass beads
Fig. 4: "COP" micro shot peening device
Fig. 5: An AFM image of microdimples generated on chrome-bearing steel SUJ2
Fig. 6: An SEM image of steel beads with PTFE affixed on the surface
Fig. 7: Crystallized layer part generated onto blasting surface SUS304
Fig. 8: An example of drilling to CFRP plate, an SEM image
MFN was able to get an interview with Hiroshi SHIMIZU, Assistant GM of Special Products Division of Itoh Kikoh Co., Ltd.
(?) MFN: We hear your company has a very long history, is this right?
(!) H.S.: Yes. Itoh Kikoh Co., Ltd. (IKK) was founded back in 1922 and has a long history of more than 90 years. Commencing with the foundry business, IKK has expanded its business to the current status running three major business units including the Foundry Division, where high-alloy casting products are produced; the Machinery Division, where various types of surface treatment machines are manufactured and custom-installed; and the Special Products Division, where we conduct production and distribution of blasting media. In addition, we have IKK Tohoku Co., Ltd., a subsidiary located in the northeastern part of Japan, the main business of which is related to semiconductor manufacturing equipment. In addition, in China, we have a subsidiary IKK (Dalian) Co., Ltd. that has just adorned the cover of MFN China, March 2014 issue. We have another China-based subsidiary IKK (Tianjin) Co., Ltd. that deals mainly with artificial sand.
(?) MFN: Please explain the blasting media manufactured by SPD - Special Products Division.
(!) H.S.: They are minuscule, spherical grains much finer than well-known steel shot, manufactured by the Nitrogen Gas-Atomizing method - we call them "beads". The beads are mainly used as blasting media for surface treatment purposes, and are of two kinds of materials, carbon steel and stainless steel. Each bead is cleanly shaped in spherical form, even with the diameter of a few tens of micrometers or less. Fig.1 shows the grain size and hardness corresponding to each product code.
(?) MFN: Would you tell us about the Gas Atomizing method?
(!) H.S.: Sure. The Gas Atomizing method was developed a few decades ago. The structure of manufacturing equipment is outlined in Fig.2. Briefly, by injecting high-pressured nitrogen gas into molten metal, microspherical beads are produced. Because the granulation process is conducted entirely in the dedicated chamber, the beads produced there are very clean and minimally oxidized on the surface.
(?) MFN: How are steel and stainless beads used, respectively?
(!) H.S.: Steel beads are served mainly for peening purposes, because of the hardness of more than HV800. The peening effect is extremely high due to the fineness and high hardness and thus, steel beads can leave great residual stress in the closest layer to the surface of the target material. Steel beads have been adopted by leading surface treatment equipment manufacturers and are contributing in reinforcement mainly of various automotive parts such as springs, gears, shafts and others.
By contrast, stainless beads are targeted mainly to the surface-cleaning market. They are utilized in cleaning applications for aluminum die-cast, rubber mold and resin mold modalities, replacing glass beads that have been ordinarily used so far. Stainless beads are very long in lifetime for they are much less breakable than glass beads. It depends on size and/or conditions, but in the following example shown in Fig.3, the lifetime of stainless beads is approximately 70 times that of glass beads. Not only the cost factor but also waste-reduction and eco-friendliness are the key reasons we get favorable reactions from the market for this bead.
(?) MFN: Can we talk about the topic of new technical approaches related to beads?
(!) H.S.: Yes, we can. We are proceeding with the "COP project" as a new attempt in the technical area of the shot peening process, in the 3-party joint research with Hatsuhiko USAMI Ph.D. from Meijo University, Faculty of Science and Technology and IKK Shot Co., Ltd.
(?) MFN: What kind of technology is that "COP"?
(!) H.S.: "COP" is abbreviated from "Condition Optimized Peening".
In typical shot-peening processing, it is necessary to inhibit surface roughness and give higher compressive residual stress to the near-surface zone. To meet these demands, blasting media tend to be further miniaturized. Nevertheless, use of fine particles generates coarse secondary particles by condensation, and the blasting of these coarse particles causes topical increase of surface roughness and generation of erosion as undesirable technical problems.
To solve these problems, we have developed a new device that can blast fine particles very effectively. Basic structure of this device is a direct pressure-type peening device, featuring a concentric double-tubed nozzle and particle tank with curved bottom base.
Media stored in the tank is conveyed into the inner tube of the nozzle by importing compressed air (of 0.1 to 0.3MPa) intermittently. Concurrently, compressed air of comparatively high pressure (greater than 0.3MPa) shall be imported into the outer tube and consequently, blasting of media to the target shall be accelerated. As understood from the above, particulate flux and blasting velocity can be controlled only by the pressure level of compressed air. This is the derivation of the "COP" - Condition Optimized Peening.
(?) MFN: Please exemplify applications of COP technology and their respective fields.
(!) H.S.: OK. By the aforementioned new COP device, extremely low particulate flux of blasting that was unavailable with conventional blasting machines has become possible. And by such low level blasting, it's become possible to build microdimples on the surface of the target (refer Fig.5). We also have confirmed it possible to give different functionality, e.g. solid lubricity and oil repellency, to the blasting surfac, by affixing ethylene fluoride around the surface of general-purpose steel beads (as shown in Fig.6). Additionally, micro-crystallization of surface part by blasting is proven to be possible as well (Fig.7).
We have near-future plans of further technical development like new modification treatment methods to the orbital plane of rolling bearing, blade edge of tools, etc. We will also investigate an application for drilling to hard-to-work materials like CFRP (Fig.8). As such, COP technology is expected in transcendent application coverage exceeding the conventional framework of shot peening.
(?) MFN: Lastly, tell us about your idea concerning IKK's future activities to the market?
(!) H.S.: It is predicted that the market trend of blasting media is directed to further refinement. As well as utilizing COP and conventional methods, we may possibly adopt the hot "AM(Additive Manufacturing)" technology for spherical, metallic microparticles. IKK is fully committed to devoting every effort to solving various technical problems and expanding market.
MFN would like to thank Hiroshi SHIMIZU for the interview!