Original Position Statistic Distribution Analysis Research Articles

Lower limit characterization of segregation degree for large-size low-alloy steel.

Based on the original position statistic distribution analysis technique, the characterization method of segregation for large-size metal materials gives significant guidance to the research of material properties and production. However, random errors are inevitably brought into the calculation of segregation degree for materials characterization by the Spark Mapping Analysis for Large Sample (SMALS) technique, resulting in a misguide of the segregation degree. In this paper, we present the lower limit of segregation degree (Ds(L)) method to distinguish the random error from metal material segregation for large-size samples over the SMALS method. The random error of standard material in the 95% confidence interval was utilized as Ds(L) and the method has been applied for macro-segregation quantitative analysis. The precision correlation between Spark Atomic Emission Spectrometry (Spark-AES) and SMALS was established. Furthermore, the functional relationship between the Ds(L) and element content C can be obtained in the SMALS method. The Ds(L) method as the criterion can be used to not only characterize the minimum limit of the segregation degree but also the segregation existence for large-size samples. Applying to low-alloy steel can illustrate the effective performance of the Ds(L) method. Results on both spark mapping analysis and Spark-AES verify the substantial consistency.

Recrystallization and diffusion mechanisms of segregation improvement in cast billets by high temperature reduction pretreatment

Controlling the segregation of alloying elements in steel can improve the uniformity of the structure and properties of the material. High Temperature Reduction Pretreatment (HTRP) is an effective technique to improve the internal quality of steel by generating plastic deformation in the core and providing the recrystallization energy. Comparative analysis was conducted to illustrate the effect of the HTRP on the internal quality of 42CrMo cast billets. To quantitatively analyze the recrystallization and diffusion mechanisms, the tested samples were measured using Scanning Electron Microscopy (SEM), Original Position Statistic Distribution Analysis (OPA) and Electron Probe Microanalysis (EPMA). The results show that the plastic deformation prompts the austenite to recrystallize. As the deformation of the HTRP sample increases, the recrystallized austenite grain size decreases significantly. It is also found that the statistical macro-segregation and micro-segregation ratios of substitutional elements Si, Mn, Cr and Mo decrease. The increase in austenite grain boundaries enables the increase in diffusion coefficient of the solid solution elements, which is the main reason for improving the segregation of the cast billet.

Effect of boron segregation on the surface crack of low carbon boron-bearing steel

Abstract Boron segregation characteristic was analysed based on segregation model and the original position statistic distribution analysis, and surface horizontal crack was observed by using metallographic microscope and scanning electron microscope. Theoretical calculation indicates that boron element has a strong segregation tendency when the solidification fraction is greater than 0.9, at the end of solidification, the boron content is about 70 times higher than the initial boron content, and the cooling rate has no obvious effect on boron segregation. The segregation in the external region was larger, and the maximum segregation of four test samples is 32.372, 18.008, 7.285 and 18.392, respectively. The micro-morphology of crack shows that the extension direction of the crack is vertical to the billet surface and the billet side, and the horizontal crack is formed by the expansion of subcutaneous micro-cracks and small bubbles in billets during rolling. The crack section is attached with metal particles and granular inclusions.

Investigation of shinning Spot Defect on Hot-Dip Galvanized Steel Sheets

Shinning spot defects on galvanized steel sheets were studied by optical microscope, scanning electron microscope(SEM), Energy Dispersive Spectrometer (EDS) and Laser-Induced Breakdown Spectroscopy Original Position Statistic Distribution Analysis (LIBSOPA) in this study. The research shows that the coating thickness of shinning spot defects which caused by the substrate defect is much lower than normal area, and when skin passed, the shinning spot defect area can not touch with skin pass roll which result in the surface of shinning spot is flat while normal area is rough. The different coating morphologies have different effects on the reflection of light, which cause the shinning spot defects more brighter than normal area.

Inclusion Distribution in Ingots Investigated by Dissection

Inclusion distribution in ingots was studied by dissection of a 16.8 t P12 ingot and a 5.0 t H13 ingot, with the analysis of T[O], original position statistic distribution analysis (OPA), metallographic microscope static analysis and small sample electrolysis. The results showed that the inclusions in ingots were uneven; a positive segregation area was found in the center and lower part of the ingot, while a negative segregation area was present in the central part of ingot top; inclusion segregation in a large size ingot was severer than that in a small one. A new concept, named inclusion segregation index, was put forward to quantify the segregation degree of inclusion. It was found that the segregation indexes drawn from T[O] analysis and OPA fit well, but they were different from those obtained by metallographic microscope static analysis and small sample electrolysis in the investigation of P12 ingot, which contained a higher sulfur content; while the segregation index drawn from T[O] analysis was close to that from metallographic microscope static analysis in the H13 ingot with a lower sulfur content.

Original Position Statistic Distribution Analysis for the Sulfides in Gear Steels

The sulfides in some different gear steels were analyzed by original position statistic distribution analysis technique. The relationship between the proportion of the frequency of high intensity signals and the content of total sulfur and total oxygen in samples has been investigated. Multi-elemental correlation on high intensity signals has been performed in order to obtain the composition and proportion of different type of sulfides. It was found that the proportion of simple sulfide was more than that of oxide-sulfide duplex inclusion in six gear steel samples. The ratio of the oxide-sulfide duplex inclusion to the total sulfides were determined by the present method and the results had good coincidence with the value obtained by quantitative metallographic method and scanning electronic microscopy. The influence of the content of Ca on the composition of the sulfides was investigated. It was found that the relative proportion of the complex inclusions of Al–Ca–Mn–O–S increase with the rise of the content of Ca in gear steels. The ratio of the content of Ca to the content of S (Ca/S) also had great effect on the relative proportion of the oxide-sulfide duplex inclusion.

Time-Series Analysis Technologies Applied to the Study of Carbon Element Distribution Along Casting Direction in Continuous-Casting Billet

The carbon element distributions along casting direction at centerline position, V-shaped segregation band, and columnar to equiaxed transformation (CET) position in continuous-casting billet have been first obtained by the original position statistic distribution analysis (OPA). Different location points at a certain position were formed along the opposite direction of casting direction with the lapse of the time, so the carbon mass fractions of different location points at a certain position can be considered as a time series. Based on the actual result, some typical time-series analysis technologies, such as the autoregressive integrated moving average (ARIMA) model, were used to analyze the characteristics of the three time series. It is found that there is some periodicity in the carbon element distribution at centerline position, and the correlation relationship between centerline position and CET position is closer than that between the centerline position and V-shaped segregation band at the same location point along the casting direction. Moreover, the element distribution along the casting direction is one of the solidifying results with the lapse of the time, so it is possible to investigate the characteristics of the system about the solidification process of continuous-casting billet by using these time series. Then it shows that there is a chaos feature in the system about the solidification process of studied continuous-casting billet on the basis of Hurst exponents and saturated correlative dimensions. Meanwhile, the formation process of carbon element distribution along casting direction can be described as fractional Brownian motion, and the upper and lower limits of the number of internal independent variables were determined in order to describe the formation process of carbon element distributions at different positions of the studied billet. Finally, the stochastic extent at V-shaped segregation band is found to be the largest, and it needs more independent variables to describe its formation process than the other two positions.

Original Position Statistic Distribution Analysis of Trace Element Segregation in Nickel-base Super Alloy by LA-ICP-MS

Original Position Statistic Distribution Analysis of Trace Element Segregation in Nickel-base Super Alloy by LA-ICP-MS

Non-Metallic Inclusion Distribution in Surface Layer of IF Steel Slabs

Non-metallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis (OPA) method. It was found that most non-metallic inclusions larger than 10 pm existed in the subsurface layers of 0. 5–3. 5 mm from the slab surfaces and very few large non-metallic inclusions were found in the inner regions (≥4. 5 mm from slab surfaces). In addition, it was found that at high casting speed level (1.4 m/min), even a slight change of casting speed could result in a remarkable increase of the non-metallic inclusions. Thus, at high casting speed, changing the casting speed should be avoided or considerably lower speed changing rate must be used.

Distribution and segregation of dissolved elements in pipeline slab

The chemical composition in a cross section of a high grade pipeline slab was measured point by point (in a scale of 1 μm) using original position statistic distribution analysis (OPA). The result indicated that negative segregation strips of Si, Mn, Mo, Ni, Cr, Nb, Cu, Ti, and V exist in the two sides 24 mm away from the central line, with a width of 8–12 mm, Negative segregation inside the central line is more severe than that outside the central line, and the highest positive segregation of the elements appears closely by the inner sides of the negative segregation strips. No obvious negative segregation strip of S and P is found. Segregation of the elements in the central area is higher than that in the outer and inner arc areas. The segregation of C, Ti, S, and P is high and that of Cr, Cu, Si, and Mn is low in the slab.

Original Position Statistic Distribution Analysis (OPA)-Novel Statistic Characterization Method of Different Chemical Compositions and its States of the Materials

Original position statistic distribution analysis (OPA) is a new analytical method to determine the quantitative distribution of different chemical compositions and their states of the materials. A novel quantitative metal original position analyzer has been invented by combining the technology of Single Discharge Analysis (SDA) and continuous scanning excitement spark spectrum without pre-excitement. This analytical method can be used to analyze the original position statistic distribution of metals. In this study, the following examples were provided: Quantitative statistic distribution of contents of various elements on the deferent locations in materials; Quantitative statistic distribution of weight in deferent contents of the various elements; Accurate calculation of the segregation of various elements in materials; Quantitative description of the homogeneity of materials; Quantitative statistic distribution of weight in different contents of the elements in total excitement signals of materials; Quantitative description of the porosity in materials; Quantitative statistic distribution of inclusion contents on different locations in materials and distribution of inclusion sizes in materials. The concept of original position statistic distribution analysis along with the widely utilization of the metal original position analyzer will provide researchers and scientists a new method to study the internal characteristics and predict the properties of the materials

Determination of Inclusions of Boron and Titanium in Steel by Original Position Statistic Distribution Analysis Technique

A new method for the determination of inclusions of boron and titanium in medium and low alloy steel has been reported in this paper. The technique of original position statistic distribution analysis based on statistic analysis of more than ten thousands primary optical signals is applied in the present method. It is found that the abnormal high intensities in emission lines of boron and titanium occurred when a discharge volatilizes the material containing inclusions of boron and titanium. Some statistic algorithms are developed to distinguish the signals related to nonmetallic inclusions from the signals generated from soluble boron and titanium. Furthermore, mathematical models based on the relationship between the frequency of abnormal sparks and content of inclusions is put forward in this paper to count the contents of inclusions of boron and titanium. The results calculated by the present model have good coincidence with the value obtained by chemical methods. The present method has been applied to the determination of the contents of inclusions of boron and titanium in some certified reference materials and some real medium and low alloy steel samples.

Analysis of the Welding Materials by OPA Technique

Original position statistic distribution analysis (OPA) technique is a new kind of analysis method that can be used to detect the segregation, porosity and non-metal inclusion of iron and steel material. In the present paper, the technique has been applied to analyze two middle and low alloy welding plate samples. One sample is normal and there is no any defect in its welding seam, whereas the other sample has one obvious little defect in its welding seam. For each sample, both the welding seam and the mother material were scanned and analyzed, and the continuous content distribution of each element in scan area was thus accurately obtained. From the content distribution map, the weld shape and the transition zone were directly observed. By using the content curve from mother material to the welding seam, the content change range and its change gradient were calculated. These two parameters were suggested to evaluate the quality of the welding seam and the welding technology. For the sample with the little defect, in its defect region the contents of C and S presented higher, whereas the contents of metal elements such as Ni, Cr, Mn, Mo, Al presented lower. This result gave the reason why its mechanics property was relatively bad. It was suggested that the defect completely resulted from another kind of material.

Original Position Statistic Distribution Analysis for Al Inclusion in Continuous-Casting Thin Slab

Single discharge analysis and comparison of signals of multi-channels, two kinds of technique of Original position statistic distribution analysis, were used to analyze and evaluate the Al inclusion in continuous-casting thin slab. The samples are continuous casting slab . Datum of Al inclusions such as average concentration and concentration distribution , types of inclusion, concentration of the different type of Al inclusion, size distribution are obtained on different sect of cross section and the whole cross section of the sample.

Correlation Analysis of MnS Inclusion Composition Using Original Position Statistic Distribution Analysis

In the process of Original Position Statistic Distribution Analysis, many abnormal higher spark signals exist. They are believed as inclusion signals. Analyzing the time sequence and position of the abnormal spark, It is found that the higher spark signals for S and Mn will appear simultaneously . The reason is that MnS inclusion caused the element concentration enrichment at these zone. Mixing some pure MnS crystal in pure iron powder and pressed by Heat Isostatic Pressing technology, reference samples of MnS inclusion were made . Criteria of abnormal higher spark signals for Mn and S is the measured value from the “blank sample ”.After analyzing the spark behavior of these reference samples using OPA instrument, we can calculate the MnS inclusion concentration through such method. steel samples were analyzed and results is satisfactory.

Influence of Casting Speed Variation during Unsteady Continuous Casting on Non-metallic Inclusions in IF Steel Slabs

The influence of casting speed variation on non-metallic inclusions in surface layers of IF steel slabs during continuous casting were investigated with OPA (Original Position Statistic Distribution Analysis) method. It was found that, when the casting speed was evenly decreased from 1.4 to 0.6 m/min, increases of the nonmetallic inclusions owing to the increase of the mold powder entrapment were observed only on those slabs which were cast at the start of casting speed change. While, in experiment of increasing casting speed evenly from 0.6 to 1.4 m/min, increases of nonmetallic inclusions were observed only on slabs which are cast at the time when the casting speed was stopped to increase after it had been increased to 1.4 m/min. For slabs which were cast during the casting speed evenly increasing or decreasing period and at the time when increasing or decreasing the casting speed at low casting speed level (0.6 m/min), the influence of casting speed change was very small. In addition, it was found that, at high casting speed level (1.4 m/min), even a little change of casting speed could result in remarkable increase of the non-metallic inclusions. Thus, at high casting speed, changing casting speed should be avoided or using much slower speed changing rate.

Original position statistic distribution analysis study of low alloy steel continuous casting billet

The homogeneity of low alloy steels continuous casting billet obtained under different technological conditions has been investigated by original position statistic distribution analysis technique. On the basis of systematic analysis of ten thousands primary optical signals at the corresponding original positions, the quantitative statistic distribution information of each element was obtained. The biggest degrees of segregation of low alloy steel continuous casting billet were calculated accurately according to the quantitative distribution maps of the contents. It was suggested that the weight ratio in a certain content range was used to judge the homogeneity of the materials, and the two models—the total weight ratio of contents (the degree of statistic homogeneity, H) within the permissive content range (C0±R) and the median value confidence extension ratio (the degree of statistic segregation, S) at 95% of confidence limit of weight ratio—were put forward. The two models reflect the composition and state distribution regularity of the metal materials in a large region. The difference between the sample with high columnar crystal and the sample with high equiaxed crystal has been studied by using the two models.

Original position statistic distribution analysis (original position analysis) ——A new analytical method in research and quality evaluation of materials

Original position statistic distribution analysis (OPA) is a new analytical method to determine the quantitative distribution of different chemical compositions and their states on a big scope of the materials. A new quantitative metal original position analyzer, which was invented based on the analysis technology of single discharge analysis (SDA) and a continuous scanning excitement spark spectrum without pre-excitement, can be used effectively to analyze the original position statistic distribution of the metals. Thus, the new information of the materials, such as the quantitative statistic distribution of contents of various elements and inclusions on different positions in the materials, the distribution of the size of the inclusions, can be obtained. The technique can also be applied to the accurate calculation of the segregation of various elements in the materials, as well as the quantitative description of the homogeneity and porosity of the materials. The concept of the original position statistic distribution analysis along with the wide utilization of the metal original position analyzer will provide researchers and scientists a new method to study the inside characteristics and properties of the materials.