Strip Defects Research Articles

SSPによる板波探傷システムの高性能化

In order to improve the defect detectability of Lamb wave inspection system conventionally used for on-line detection of internal defects of steel strip, application of non-linear signal processing, SSP (split spectrum processing), to Lamb waves and the optimization of the SSP parameters were investigated. Sample strips with natural defects were used to evaluate the performance of SSP in this research. As a result, the improvement of the sensitivity of Lamb wave inspection was confirmed by optimum selection of SSP parameters. Furthermore, real-time processing of SSP was realized. Consequently, the newly developed Lamb wave can perform SSP at a 500 Hz repetition rate that is sufficiently high repetition rate for the on-line Lamb wave inspection system.

The Present State and its Future of Sensor Technology in Iron and Steel Industry

In the past decade. strip defect sensing technologies In the Japanese steel Industry developed rapidly to meet the quality requirements for steel strip that have grown Increasingly stringent. To Increase the accuracy of In-line surface defect Inspection In continuous annealing and processing. electrolytic tinning and continuous galvanizing lines. several hardware Improvements have been made. such as a shift from the mono-receiver type to the multi-receiver type and the development of the photo-conductive rod receiver to obtain uniform optical Information across the width of strip. In the area of software. significant developments have been made In the signal processing technology to separate and distinguish the specular reflection from the diffuse reflection. Also. characteristics extraction technologies utilizing neural networks are now In practical use. The Internal defects detected by today's on-line leakage flux sensing technology are of the order of several pp‘s. In addition to these Improved and newly developed pattern recognition technologies. more advanced process monitoring technologies using neural networks. such as diagnosing the operating condition Inside the blast furnace and the prediction of breakouts In the continuous casting process. are also In use. This paper discusses the present state of these new sensing technologies and their future outlook.

Effect of residual stresses and complex loadings on the fatigue behavior of underclad cracks

The objective of this paper is to show that the fatigue crack propagation of cold underclad cracks in reactor vessel nozzles is much less than predicted by the usual conservative safety assessment methods, and that it is possible to estimate real margins more accurately. The crack propagation of underclad cracks was assessed by numerical methods with conservative safety hypotheses: • - the upper bounds of fatigue crack propagation laws in an air environment have been used for both the base metal and the cladding, • - fatigue crack initiation on the actual underclad defects has not been taken into account, • - the crack lengths have been corrected using Irwin's correction, which accounts for plastic-zone sizes at crack tips, • - elliptical defects have been considered to be strip defects, • - the lower bounds of the yield strength and thoughness of the materials have been used. An extensive experimental fatigue program was also performed on large specimens in several laboratories. The specimens were taken out of a full-size nozzle (SA 508 Cl.3 steel) containing cracks in the heat-affected zone under the three layers of cladding. The experimental observations are as follows: • - a significant fraction of the lifetime is spent in crack initiation, • - the crack growth rate is lower because of a non-aggressive (inert) environment in the defects, • - the residual stresses at 300°C can be neglected, • - the residual stresses at room temperature are significant. The numerical calculations of crack propagation, taking into account the residual stresses, load ratio and temperature effects, give a fair estimate of the behavior of the underclad cracks observed during testing. Combining the experimental and numerical results provides a good knowledge of the real margins between the actual underclad crack propagation and the propagation that was calculated in previous safety assessments. It can be concluded that the actual propagations of underclad cracks will be very small or even negligible during the specified lifetime of the components.

Defects in Platinum Silicide Formation

ABSTRACTFour types of cause related defects in the formation of platinum silicide were examined by scanning Auger Microscopy (SAM). These are: “Dark Platinum”, a dark rough patch on the platinum silicide, “Aqua Regia Attack”, the apparent etch of the platinum silicide by the aqua regia used to remove pure Pt metal, “Spot Defects”, holes in the Pt-Si layer and Ti-W strip defects, the apparent defects left in the Pt-Si by the stripping of a Ti-W overlayer. Elemental Auger maps show that silicide formation was prevented, in the first three cases, by remaining oxide from a masking step. The fourth case was caused by a layer of titanium oxide overlying the Pt-Si.

Sendzimir mill computerization in BSC Stainless

While the number of computers being used in the iron and steel industry is increasing rapidly, the number appearing in the area of single-stand cold mills is still relatively small. However, in recent years a number of Sendzimir mills rolling stainless steel have been fitted with computer control. Among these are the systems being installed with the new high-power ZR21 B–63in mills at the Shepcote Lane Works of BSC Stainless. The need for these computer systems was considered at the feasibility-study stage of the project and the justification was based on estimates of savings resulting from improvements in mill utilization by using optimized rolling schedules and by reducing the mill reversal time between each pass and for slow running at strip defects. Work on the development of mathematical models of the Z mill cold-rolling process has shown that, for a given set of coil and mill particulars and operating constraints, optimized rolling schedules could be produced which best utilize the high-power capabilities of the mill. By storing these rolling schedules in the computer and using them consistently, the production performance of the mill can be maintained at an optimum level. The paper gives brief details of the mills, the computer, and peripheral equipment, and describes more fully the computer-controlled functions to be provided. Plans for implementing these functions in four stages are given and progress is reported since commissioning of the first of the two mills in February 1977.

Surface defects of strip rolled in 20-roll stands

Surface defects of strip rolled in 20-roll stands