Jippei Suzuki

Bonding process of Al/Cu dissimilar bonding with liquefaction in air

Sample materials were industrial grade pure aluminum (A1070) with a diameter of 6 mm and pure copper (C1020) round rod. In order to simplify the obtainment of test samples for observation 10 mm test samples were used for both aluminum and copper. As preprocessing of the bonding surface, wet grinding was performed using #2000 water resistant sand paper and then oil was removed using acetone. As shown in figure 1, during the bonding test, as the bonding surfaces were placed together in the center of heating of a furnace, support test pieces using the same material as the respective test pieces were used on the outside of both test pieces. 1. Summary

Cutting Properties of Austenitic Stainless Steel by Using Laser Cutting Process without Assist Gas

Recently, laser cutting is used in many industries. Generally, in laser cutting of metallic materials, suitable assist gas and its nozzle are needed to remove the molten metal. However, because of the gas nozzle should be set closer to the surface of a workpiece, existence of the nozzle seems to prevent laser cutting from being used flexible. Therefore, the new cutting process, Assist Gas Free laser cutting or AGF laser cutting, has been developed. In this process, the pressure at the bottom side of a workpiece is reduced by a vacuum pump, and the molten metal can be removed by the air flow caused by the pressure difference between both sides of the specimen. In this study, cutting properties of austenitic stainless steel by using AGF laser cutting with 2 kW CO2 laser were investigated. Laser power and cutting speed were varied in order to study the effect of these parameters on cutting properties. As a result, austenitic stainless steel could be cut with dross-free by AGF laser cutting. When laser power was 2.0 kW, cutting speed could be increased up to 100 mm/s, and kerf width at specimen surface was 0.28 mm.

Temper embrittlement in the HAZ of 2¼ Cr-1Mo steel induced by reheating after SR treatment: Study of temper embrittlement in HAZ of Cr-Mo steels (4th report)

Summary The temper embrittlement affecting the HAZ of 2 1/4Cr-1Mo steel subjected to SR treatment and subsequent reheating is investigated with synthetic HAZ specimens and compared with the embrittlement observed in specimens tempered in the same temperature range without SR treatment (direct tempering). The synthetic HAZ specimens are de-embrittled on application of suitable SR treatment (975 K × 5 hours). Subsequent reheating at 775 to 925 K, however, produces four different types of embrittlement in the specimens. These are the second, third, fourth, and fifth types of embrittlement already identified in the direct-tempered specimens. The first type of embrittlement which occurs during direct tempering in the shortest time range does not appear after SR treatment. The second type (the short-term type), which occurs over a wide time-temperature range during direct tempering, only appears in a narrow range after SR treatment. The third and fourth types (the long-term types) occur just as intensively as d...

Cutting Properties of Austenitic Stainless Steel by Using Linear Polarized CO2 Laser without Assist Gas

Recently, laser cutting is used in many industries. Generally, in laser cutting of metallic materials, assist gas and its nozzle are needed to remove the molten metal. However, because of the gas nozzle should be moved closer to the position about 1 mm from the surface of a workpiece, it is thought that existence of the nozzle causes lack of flexibility of laser cutting. Therefore, the new cutting process, Assist Gas Free laser cutting (hereafter, called as AGF laser cutting), has been developed and investigated about cutting properties in our laboratory. In this process, the pressure at the bottom side of a workpiece is reduced by a vacuum pump, and the molten metal can be removed by the air flow caused by the pressure difference between both sides of the specimen. On the other hand, when cutting of metallic materials with a linear polarized laser is performed, it is known that the cutting kerf might slant. This phenomenon is also observed in AGF laser cutting. In the present study, cutting properties of austenitic stainless steel by using liner polarized CO2 laser in AGF laser cutting was investigated. Cutting speed and direction were varied in order to study the effect of these parameters on cutting properties. As a result, when the angle formed by the cutting direction and the polarized direction of laser was parallel, the kerf slant could be depressed, and the critical cutting speed could be the fastest in any other cutting direction.

Effect of Coarse Carbide Particle on SR embrittlement in the HAZ of 21/4Cr-1Mo steel

The authors pointed out that growth of the carbide particle is related to SR embrittlement in the HAZ of 2 1/4Cr-1Mo steel in a previous study. Suitable image processing was employed to evaluate the shape of a large number of carbide particles in a SEM image. An image-dividing technique was needed in for the difference of tone in each area of a SEM image. Image processing included image dividing, brightness and contrast, as well as a contraction and smoothing operation. The shape of the particle changed from the sphere type to the needle or polygon type because of the progress of SR treatment. The change of aspect ratio of the particle in the cross-section has a good correlation with the increment of SR treatment time. However, the aspect ratio of the particles on the fracture surface did not correspond with that of the cross-section in the long time range. This was confirmed by SEM observation on a pair of fracture surfaces, where coarse carbide particles were broken into pieces. Coarse carbide particle may accelerate SR embrittlement by acting as a path for crack propagation and a crack initiation site for brittle fracture. The type of carbide particles was investigated by X-ray diffraction. M2C (Mo2C type), M7C3 (Cr7C3 type) and M23C6 (Cr23C6 type) carbides were identified in the time range of SR embrittlement. The coarse carbide observed when SR embrittlement occurred significantly was confirmed as M23C6 type by TEM observation. The calculation results based on the Eshelby theory show that the change of shape of the carbide particle can affect crack propagation of brittle fracture.

Effect of Heating Rate on Al Bonding in Air by Inserted A5056 Disk

Al bonding in air by inserted A5056 was investigated in this study. Heating rate in thermal history of bonding process may have the relation with the growth of Al oxide film and the deformation of bonding surface by softening. Both of phenomena affect the joinability and the mechanical properties of bond. Al bonding in air was carried out by several heating rate. Growth of Al oxide film significantly suppressed the progress of bonding in air by low heating rate, 1K/s. Decrease of deformation of bonding surface suppressed also the progress of bonding by high heating rate, 10K/s. In case of medium heating rate, 5K/s, good joinabilty of Al bonding in air was obtained by the medium growth of oxide film and the deformation of bonding surface.

Effects of carbon content and peritectic reaction on hot cracking of high-carbon steel weld metal

Mediumand high-carbon steels with carbon contents over 0.3 %C (machine component and rail steels, etc) have a higher hot cracking sensitivity than low-carbon steels (mild steels, etc). This is generally indicated as being due to the fact that, when alloying elements are added to the pure metal, (1) the solidification temperature range increases and (2) the final solidification temperature decreases as their content increases, thereby heightening the hot cracking sensitivity. These features correspond to the case where no special reaction occurs during solidification of aluminium-base alloys, nickel-base alloys, etc. 3 During solidification of carbon steels, ie Fe–C alloys, the peritectic reaction

Selection of parameters on laser cutting mild steel plates taking account of some manufacturing purposes

There are large number of processing conditions which can be set for laser-cutting of plate materials, because importance of the objective for the cutting is different from product to product. This study aims to build a system which can set the processing conditions reasonably and efficiently. From plural processing objectives, roughness of cutting surface was taken up from among the required qualities, such as processing speed, circularity of a processed hole, height of dross on the rear side, roughness of cutting surfaces, accuracy of shapes and dimensions, and with of burning, to review the effects of the processing condition on the cutting surface including the drag line gap. In our experiments, a 1 kW CO2 gas laser machine was used to make laser-cutting samples and 389 combinations of samples were used. From the results of the experiments, the range of processing conditions which allow cutting is defined by the energy input per unit area HIA = 4.8 [J/mm2]. The values of roughness of the cutting surface on both front and rear sides of the plates can be reduced if the cutting speed is 1000 mm/min or higher, and they little change at small values if the heat input per unit area is within a range under 20 J/mm2. In a range of thin plate thickness, the drag gap on cutting surfaces can be evaluated by the heat input per unit area. In the case of thicker plate, the greater the duty is, the smaller the drag gap is, if the heat input per units area is kept unchanged. Cutting with small heat input is desirable for better roughness of cutting surface. Cutting with large heat input is required for better drag gap. In the scope of our study, a value 20 J/mm2 of heat input per unit area is recommended for laer-cutting of 0.8 - 4.5 mm thick mild steel plates.

Four types of temper embrittlement observed in the HAZ of 2 1/4Cr‐1Mo steel: Study of temper embrittlement in HAZ of Cr‐Mo steels (1st Report)

Summary This paper describes a systematic investigation of the temper embrittlement occurring in the HAZ of 21/4 Cr‐lMo steel in the tempering temperature‐time range of 775–900 K × 0.2–10 000 hr. The transition temperature TrE of each specimen was measured, and the temper embrittlement is shown to increase with increasing TrE. The temper embrittlement is classified into four types. The first and second types of embrittlement respectively appear in the initial stage of tempering, such as at 775 K × 1 and 100 hr. They differ from the previously observed ‘low‐temperature temper embrittlement’. The secondary hardening occurring during tempering appears to play an important role in inducing these types of embrittlement. The third type appears during long‐term tempering (825 K × 100–10 000 hr). This type is equivalent to ‘high‐temperature temper embrittlement (reversible temper embrittlement)’. The fourth type occurs in the final stage of tempering (825 K × 1000–10 000 hr). Little work has been done to distingu...

Cutting of aramid fiber in A – GFRP composite

Aramid fiber is a kind of polymer that exhibits a heat-resistance of asbestos and a stiffness of glass [1]. Cutting process of the composites that contain aramid fibers is often required. The present investigation discusses the cutting process of aramid fiber in A-GFRP composite (Aramid-Glass hybrid fabric reinforcing GFRP composite). The polycrystalline diamond (PCD) cutting tool exhibits a superior performance over tungsten carbide and cermet tools, especially at high cutting speed range. Moreover, a cutting model of aramid fiber is discussed. This cutting model shows that a high edge sharpness is required to obtain a clean cut out of aramid fiber, however, there is a minimum value of undeformed chip thickness to exist aramid fracture.