Ultra Low Carbon Steel Sheets Research Articles

CW Nd:YAG laser cutting of ultra low carbon steel thin sheets using O2 assist gas

Abstract There are many non-linear interaction factors responsible for the performance of the laser cutting process. Identification of the dominant factors that significantly affect the cut quality is important. The present research aims to evaluate the CW ND:YAG laser cutting parameters (the gas pressure, laser power, and scanning speed) for 1.2 mm thick ultra-low carbon steel sheets. The effect of the cutting parameters on the cut quality was then investigated, by monitoring the variation in hardness, oxide layer width and microstructural changes within the heat affected zone (HAZ). Results revealed that good quality cuts can be produced in ultra low carbon steel thin sheets, at a window of laser scanning speed of 1100–1500 mm/min and at a minimum heat input of 337 W under an assisting O2 gas pressure of 5 bar. Higher laser power resulted in either strengthening or softening in the HAZ surrounding the cut kerfs. The oxide layer width is not affected by the energy density input, but is affected by the O2 gas pressure due to exothermal reaction.

Influence of Sulphur Content and Molten Steel Flow on Entrapment of Bubbles to Solid/Liquid Interface

The sliver defects which occur easily on ultra low carbon steel sheet are the most harmful defects, especially to automobile outer panel products. There may be many causes of the sliver defects such as nonmetallic inclusions, bubbles, surface cracks and inner cracks. However, crack formation is not a serious problem in continuously cast ultra low carbon steel because of its good ductility at high temperatures. Therefore, it is important to reduce the amount of nonmetallic inclusions and bubbles just below the slab surface. Electro-Magnetic Stirring in the mold (M-EMS) is an effective tool to remove such bubbles and reduce the amount of the sliver defects, although the effects of M-EMS on the reduction in sliver defects are influenced by the chemical composition of steel, especially by the sulphur content. The slabs cast at No.4CC-1 st strand in Kakogawa Works reveal rather a high content of bubbles when the sulphur content is higher and M-EMS is not applied. In this study, the reason why sliver defects caused by bubbles are more likely to occur on steel of higher sulphur content is discussed based on the interaction between advanced solid/liquid interface and bubbles. The forces acting on the bubbles are theoretically described as a function of bubble radius, velocity and interfacial tension gradient of liquid steel in front of a solid/liquid interface.

極低炭素鋼板の歪時効速度に及ぼすMnの影響

極低炭素鋼板の歪時効速度に及ぼすMnの影響

1324 窒化ULCS薄鋼板の疲労強度と硬さとの関係(S21-3 表面改質処理,S21 金属材料の疲労特性と破壊機構)

The comparison and relations between fatigue strength with hardness were investigated using eight types of specimens; un-nitrided and ion-nitrided specimens. The fatigue properties of the ultra-low carbon steel sheets (ULCS) have been assessed by evaluating fatigue strength and hardness profile using fully reverse plain bending fatigue testing machine at constant speed of 2000 rpm with the capacity of 49Nm, microhardness tester, an optical microscope and scanning electron microscope (SEM). It was found that ion nitriding improves the fatigue strength by increasing the nitrided layer depth, however the compound layer was found not to have a dominant effect on the fatigue strength. The comparison of test result between un-nitrided and ion-nitrided specimens has shown that the fatigue strength increases up to 37% which could be reached by ion-nitriding process.

極低炭素鋼板の粒成長性に及ぼすTi量の影響

極低炭素鋼板の粒成長性に及ぼすTi量の影響

極低炭素BH鋼板の歪時効速度に及ぼすMoの影響

極低炭素BH鋼板の歪時効速度に及ぼすMoの影響

9732685 Strength of spot-welded joints of ultra-low carbon steel sheet Kosuke Kawai, Shoji Kojima (Fuji Heavy Industries Ltd.)

9732685 Strength of spot-welded joints of ultra-low carbon steel sheet Kosuke Kawai, Shoji Kojima (Fuji Heavy Industries Ltd.)

The influence of blaxial stretching on the texture of ultra low carbon (ULC) steel sheets

Multistage deformation in sheet metal forming involves changes in strain path and strain rate. Strain path and strain rate variations affect work-hardening behavior and, the final useful strain before fracture. It is well known that an abrupt change in strain path may be accompanied by inhomogeneous deformations and unusual stress-strain curves. Wagoner and Laukoins analytically and experimentally studied two-staged uniaxial-biaxial tension and they identified two different patterns of work-hardening behavior in sheet metals, namely, ferritic-type and brass type. This paper presents a study of the influence of strain path on the yield strengths of two different ULC steel sheets exposed to uniaxial tension and biaxial deformations. The effect of initial and developed texture on the initial flow strength compared to monotonic flow strength is also presented.

低炭素鋼およびTi添加極低炭素鋼フェライト域熱延鋼板の集合組織

Textures of warm rolled low carbon and Ti-bearing ultra low carbon steel sheets have been investigated. The main orientation of the recrystallization texture of the low carbon steel sheet is near {114}〈110〉, while that of the Ti-bearing ultra low carbon steel sheet is near ND\varparallel〈111〉.To explain the different formation of texture between the steels, their recrystallization behavior has been studied in detail. The study shows that the low carbon steel preferentially recrystallizes from near ND\varparallel〈100〉 grains, and the Ti-bearing steel from near ND\varparallel〈111〉 grains. The difference in the preferential nucleation site relates with the recrystallization retarding effect.Microtextural measurements by electron channeling pattern reveals that the orientation of grains recrystallized in the vicinity of grain boundaries between two near ND\varparallel〈111〉 grains greatly differs between the two steel. This difference yields by carbon in solution. A further study using transmission electron microscopy and selected area electron diffraction shows that in the presence of carbon in solution, {114}〈110〉-{112}〈110〉 orientations are formed in the vicinity of grain boundaries by some unique crystal rotation different from that occurring in the matrix. The occurrence of the unique crystal rotation is explained by the variation of active slip systems due to the interaction between dislocations and the interstitial atoms by work hardening.It is concluded that the essential factors affecting the formation of the recrystallization texture of warm rolled sheets are carbon in solution and the retarding effect on recrystallization.

極低炭素鋼板のりん酸塩処理性および穴あき腐食に及ぼす鋼中Pの影響

極低炭素鋼板のりん酸塩処理性および穴あき腐食に及ぼす鋼中Pの影響