Extra Low Carbon Steel Sheets Research Articles

Model for Predicting Recrystallization Behavior of Cold Rolled Extralow Carbon Steel Sheets

Microstructual observations indicate that the recrystallization of cold rolled extralow carbon steel sheets occurs due to the abnormal growth of selected subgrains in recovered subgrain microstructures. The authors measured the orientations of a recovered microstructure of a cold rolled extralow carbon steel sheet by SEM-EBSP and classified the deformed grains into several types due to the orientation and its scattering degree. In this study, a model for predicting the recrystallization behavior of cold rolled extralow carbon steels has been developed by applying the model of Humphreys modified to the grain of each type.A good agreement between the experimental and calculated results using the model developed was obtained.

Influence of Carbon on Mechanical Properties of Cu bearing Extra Low Carbon Steel Sheets

AbstractThis paper examines the effect of carbon (C) on solid solution strengthening, bake hardening and anti‐strain aging property for copper (Cu) bearing extra low carbon (ELC) steel sheets. For this purpose, five ELC steels that contain different content of C were selected. We have investigated the effect of C on mechanical properties and microstructures for the continuous annealed ELC steel sheets. Mechanical properties and microstructures were analyzed as well using uni‐axial tensile test and electron back‐scattered diffraction (EBSD) technique following pilot rolling and continuous annealing. It has been found that the addition of C increases the solid solution strengthening as well as 19.9MPa per 0.0010wt%C in yield strength. What is more, the addition of C increases the bake hardenability (BH) as well as 18.7MPa per 0.0010wt%C. In addition, the addition of C delays the recrystallization during continuous annealing process. From an industrial standpoint, it is possible to control both a stable anti‐strain aging property and high bake hardenability for the ELC steel sheets without Ti and Nb addition.

Model for Predicting Recrystallization Behavior of Colled Rolled Extralow Carbon Steel Sheets

Model for Predicting Recrystallization Behavior of Colled Rolled Extralow Carbon Steel Sheets

Influence of Initial Microstructure on Mechanical Properties of Cu Bearing Extra Low Carbon Steel Sheets

This paper examines the effect of initial microstructure after hot rolling on the final microstructure and mechanical properties for Cu bearing Extra Low Carbon(ELC) Steel Sheets. For this purpose, two ELC steels having different initial microstructures due to different onset time of cooling after pilot hot rolling (0.4 and 1.2 second) were selected. Mechanical properties and microstructures were analyzed as well using uni-axial tensile test, electron back-scattered diffraction (EBSD) technique following pilot rolling and continuous annealing. It has been found that the reduction of onset time of cooling gives rise to the grain refinement in hot rolled sheets. The average grain sizes of hot rolled sheetss at the onset time of 0.4 and 1.2 second are 16.7μm and 20.8 μm, respectively. In addition, the planar anisotropy of the Cu bearing ELC steel sheets has improved with reducing onset time of cooling after hot rolling. However, other mechanical properties such as strength and elongation of annealed steel are similar to both cooling condition.

Tensile Properties of Chromium-bearing Extra Low Carbon Steel Sheets

The influence of chromium on tensile properties of cold-rolled and annealed extra low carbon steel sheets was investigated. Tensile strength increased with an increase in chromium content whereas elongation decreased. Yield strength showed the minimum at chromium content of 5%. The yield strength in each steel changed with ferrite grain diameter according to Hall–Petch relationship. The coefficient in Hall–Petch equation linearly decreased with an increase in chromium content. Since ferrite region hot-rolling and generation of α′ phase did not affect the coefficient, the change can be attributed to reduction of solute carbon at grain boundaries by chromium carbide precipitation. The slope of the decrease in the coefficient per 1 mass% chromium was 0.02 MPa·m1/2. The friction term in Hall–Petch equation showed the minimum at chromium content of 5% like the yield strength. The change in the friction term is the reason why 5% Cr steel inhibited the minimum yield strength. Aging at 150°C made the friction terms of low chromium steels up and friction term became to show linear relationship for chromium content. This result indicated that the lowest yield strength which 5% Cr steel showed is attributed to the retardation of aging by chromium during cooling after the annealing. It is concluded that solute chromium exhibited solid-solution strengthening. The increase in solid-solution strengthening of yield strength is about 5.6 MPa per 1 mass% chromium.

溶接缶向け新 Nb-B 複合添加極低炭素鋼板の開発

溶接缶向け新 Nb-B 複合添加極低炭素鋼板の開発

Effect of process parameters on product surface finish and thickness variation in hydro-mechanical deep drawing

Hydro-mechanical deep drawing combines the features of conventional deep drawing and hydroforming. In this process, the punch deforms the blank to its final shape by moving against a controlled pressurized fluid. Hydro-mechanical deep drawing offers several advantages over conventional deep drawing like higher drawability, uniform strain distribution, better surface finish and improved dimensional accuracy. The process parameters such as initial pressure in the chamber (pre-bulging pressure), the peak chamber pressure (cutoff pressure) and oil gap have strong influence on the process. In view of this, the effect of the pre-bulging pressure and the cutoff pressure on thickness distribution and surface finish in hydro-mechanical deep drawing were studied in this paper. Experiments have been carried out on extra-low carbon steel sheets by varying these parameters. It was found out that thickness distribution along cup wall is more uniform for intermediate pre-bulging pressures. At too low pre-bulging pressure necking takes place at punch corner (similar to the conventional deep drawing) and at very high pre-bulging pressure, necking shifts towards wall region. So a region of safe pressure (combination of pre-bulging and cutoff pressure) was found out in which cups of better quality in terms of uniform thickness distribution and better quality surface can be drawn successfully.

Improvement in formability of tailor welded blanks by application of counter pressure in biaxial stretch forming

The use of new manufacturing concepts and advanced materials is of major interest to manufacturers of automobile and aerospace parts to reduce weight and cost and improve part performance. Despite numerous benefits associated with the use of tailor welded blanks (TWBs), forming of TWBs is challenging due to a significant reduction of formability associated with these materials. The importance of hydro forming of sheets is increasing, especially in the case of materials with low formability. The present paper investigates formability of tailor welded blanks of extra low carbon steel sheets in hydro-mechanical stretch forming. The effect of counter pressure and friction between the punch and the blank on limiting dome height and strain distribution has been investigated. Weld line movement has also been studied. Though the counter pressure increases limiting dome height, it has been found that simultaneous application of counter pressure and lubrication leads to higher stretchability and greater uniformity of strain distribution. The process has also been simulated using finite element method and results have been compared with experimental data.

OS11(6)-26(OS11W0284) Effect of Sn Content on Fatigue Properties of Extra-Low Carbon Steels

The requirement of the high processing high strength light steel sheet recently rises in the car from the global environmental problems and so on from the body lightening because of fuel expenses and the view point of the safety improvement at the time of the collision. Extra-low carbons steels, commonly known as Interstitial Free steels (IF) have been widely used for automobile plates because of their excellent fabrication characteristics such as high formability, low deformation resistance, fine surface finishing and excellent weld ability. IF steels are developed by avoiding interstitial elements such as carbon and nitrogen in order to obtain superior forming properties. Substitution elements such as manganese or silicon are added to compensate the decrease in material strength caused by small carbon contents. The objectives of this study were to investigate the effect of Sn (tin) content on the fatigue strength and fatigue crack behaviors of extra-low carbon steel sheets with different Sn (tin) content varied from 0.002 to 0.22% mass. The materials were initially hot-rolled, then cold rolled to 1.4mm thick steel sheets and annealed at 650℃. Sheet materials were cut and machined to 30×90mm specimen's longitudinal side parallel with the rolling direction. All specimen have been tested using the plain bending fatigue-testing machine at 30Hz with capacity of 1.96Nm. Successive replica observation methods were performed to observe the surface crack initiation and propagation behaviors. The microstructures of each material were observed using optical microscope. In addition, the scanning electron microscope (SEM) was employed for the fracture surface observation. The main results in this test are as follows. (1) The fatigue strength by 1×(10)^7 cycles of extra-low carbon steel increased with increasing Sn (tin) content. (2) The grain size of materials with increasing Sn (tin) contents. (3) The fatigue cracks initiate from the surface of specimen and propagated mainly in intergranular mode for all materials. According to the relation of crack length and number of cycles, the fatigue crack growth rates decrease with increasing tin contents. (4) A non-propagating crack cannot be observed in the specimen subjected under the stress level of fatigue limit by 1×(10)^7 cycles.

1%Mn-0.034%Ti添加極低炭素鋼板の変態集合組織に及ぼす微量炭素添加量の影響

1%Mn-0.034%Ti添加極低炭素鋼板の変態集合組織に及ぼす微量炭素添加量の影響

Effects of centerline macrosegregation on necking of P-added extra low carbon steel sheet

Effects of centerline macrosegregation on necking was examined by the stretching experiment for cold rolled P-added extra low carbon steel sheets. The centerline macrosegregated zone containing high concentration of Mn and P was elongated in the rolling process. The elongated macrosegregated zone induced instability in the strain state when the sheet was stretched, thus resulted in the waved sheet surface. The formability of cold rolled steel sheet was deteriorated due to the wave formed by the macrosegregation. The waved surface was thought to be caused by the higher hardness in the macrosegregated zone compared to the segregation free zone. The experiments on the stretching of sheet including macrosegregation showed that the macrosegregation was the important source of instability in that of the cold rolled steel sheets. A 3D FEM analysis was carried out for the quantitative evaluation of waved surface. It was confirmed that the main source of the waved surface was the macrosegregation. Stretching in the transverse direction under the plane strain condition made the cold rolled steel sheet more inhomogeneous than stretching in any other strain condition. The thickness difference in the stretched sheet was linearly increased when the ratio of hardness in the macrosegregated zone to that of the segregation free zone was increased. The macrosegregation formed in the internal crack close to the surface was more harmful to the formability in the cold rolled steel sheet than the centerline macrosegregation.

Influence of Grain Refinement of Hot Band and Cold Rolling Reduction on the Formation of Textures and R-Value of Cold Rolled Plain Extralow-Carbon Steel Sheets

A textural analysis was carried out to explain the cause of the planar anisotropy of r-value of cold rolled plain extralow-carbon steel sheets. For a detailed analysis, a model for calculating r-values from ODF-data of texture was applied and the influence of each or a group of crystal orientations of the recrystallization texture on the planar anisotropy of r-values was studied. The following results were obtained:A development of {111}〈110〉−{443}〈110〉−{332}〈110〉−{221}〈110〉 enhanced the V-type planar anisotropy of r-values. A decrease in the intensity of these orientations by increasing the cold rolling reduction or the refinement of the hot band microstructure reduced the r-values in L and C directions and hardly affected the r-value in D direction, and as a result, the V-type planar anisotropy of r-values was improved. On the other hand, an increase in the intensity of {111}, {334} orientation by increasing the cold rolling reduction or the refinement of the hot band microstructure raised r-values in sequence of L < D < C directions and contributed to the reduction of V-type planar anisotropy of r-values as a whole.

Effects of Copper, Nickel, Chromium and Tin on Mechanical Properties of Titanium-bearing Extralow-carbon Steel Sheets.

The effects of copper, nickel, chromium and tin additions on the mechanical properties of extralow-carbon titanium-bearing continuous annealed steel sheets were studied. The following are the findings obtained:(1) Copper and chromium additions up to approximately 0.2% each increased tensile strength and decreased total elongation and the r value.(2) With the specimens each containing 0.2% copper and 0.2% chromium, lowering the slab reheating temperature to 1050°C decreased tensile strength and increased total elongation and the r value.(3) Nickel addition up to 0.12% produced no significant effect on tensile properties and the r value.(4) Tin addition up to 0.085% increased tensile strength and decreased total elongation and the r value. With the specimens containing tin, lowering the slab reheating temperature did not improve their total elongation and r value.(5) The effects of copper, nickel, chromium and tin contents on mechanical properties proved to be proportional to the difference in the atomic radius between iron and these allowing elements.(6) Copper, nickel, chromium and tin proved to produce different effects on the r value. With the specimens containing copper, nickel and chromium having slightly larger atomic radii than that of iron, lowering the slab reheating temperature improved their r value. With the specimens containing tin having a significantly larger atomic radius than that of iron, by comparison, lowering the slab reheating temperature produced only a small effect.

Simulation of the deformation textures induced by deep drawing in extra low carbon steel sheets

Predictions were made of the texture changes that are expected to take place during the deep drawing of extra low carbon IF steels. The simulations were carried out using a rate dependent theory for mixed {112}- and {110} <111 > slip. Three grain interaction models were employed, based on the full constraint (FC), relaxed constraint (RC) and least work (LW) theories. It is shown that the experimentally observed grain reorientations are reproduced reasonably well using the full constraint and least work models. The orientation dependences of the preferred deformation modes are described, together with the relative stabilities of the expected end textures.

Effect of Deep Drawing on Texture Development in Extra Low Carbon Steel Sheets

Effect of Deep Drawing on Texture Development in Extra Low Carbon Steel Sheets

Textures induced by tension and deep drawing in low carbon and extra low carbon steel sheets

The texture evolution induced by tensile deformation and by deep drawing was investigated. For this purpose, the textures of 3 types of steel (rimmed, Al-killed drawing quality, and interstitial free) were measured and analyzed using the series expansion method. The results indicate that the initial texture changes drastically after a few percent of plastic strain and evolves towards a single orientation for which the <110> direction is aligned with the tensile or drawing axis. The distinct earing behaviors of the AKDQ and IF steels (i.e. 4-eared for the Al-killed and 6-eared for the interstitial free) are interpreted in terms of differences in the sharpness and homogeneity of their ND-fibres and in the influence of the {332} <110> and the partial {223} fibre.

Ti添加極低炭素冷延鋼板の析出物制御による焼付硬化性

Ti添加極低炭素冷延鋼板の析出物制御による焼付硬化性

Effects of Alloying Elements and Hot–Rolling Temperature on Textures and r¯ Values of Continuous–Annealed Extra Low Carbon Steel Sheets

The effects of hot rolling temperature and alloying elements on the textures and r ¯ values of cold rolled and annealed extra low carbon steel sheets have been investigated. The steels examined were one extra low carbon Al–killed steel and two Ti–IF (Interstitial Free) steels with or without phosphorus. (200) pole figures and relative intensities of various reflections from the rolling plane were determined for hot bands and annealed sheets. The hot rolled textures are found, when finish-rolled at about 900°C, random regardless of the steels tested. when the finish rolling temperature is lowered to the ferrite region temperature of 750°C, however, the principal preferred orientation of (100)[011] is developed. r ¯ values of annealed sheets are decreased with decreasing the finish rolling temperature. This could be related to the presence of the stronger (100)[011] component, which is originated from the texture inhomogeneity in the through thickness direction of the hot bands at 750°C. The steel having the lower r ¯ value revealed the higher yield point elongation which is closely related to the solute carbon content in the steels. The major component of the recrystallization texture was near {554} irrespective of the steels tested, but the intensity of (100)[011] component was increased with decreasing the finish hot rolling temperature.

Textures of Warm Rolled Low Carbon and Titanium Bearing Extra Low Carbon Steel Sheets

Textures of Warm Rolled Low Carbon and Titanium Bearing Extra Low Carbon Steel Sheets

Textures of low carbon and titanium bearing extra low carbon steel sheets hot rolled below their AR3 temperatures

The textures of warm rolled low carbon and Ti-bearing extra low carbon steel sheets have been investigated using ODF's ECC-ECP (electron channeling contrast-electron channeling pattern) and selected area electron diffraction and the following results were obtained: (1) The main orientation of the low carbon steel sheet was near {113}〈110〉 while that of Ti-bearing extra low carbon steel was near 〈111〉//ND. (2) The recrystallization of the low carbon steel occurred mainly from deformed {100} grains while the main nucleation sites in the Ti-bearing extra low carbon steel were the grain boundaries of the deformed {111} grains. (3) The main orientations of grains recrystallized from deformed {100} grains are {100}〈110〉−{112}〈110〉 for both steels. (4) The orientation of the grains recrystallized from the deformed {111} grains of the Ti-bearing extra low carbon steel is mostly near 〈111〉//ND and that of the low carbon steel is mainly near {114}〈110〉. This difference is discussed in terms of the influence of carbon in solution on the crystal rotation at nucleation sites. (5) It is concluded that the different recrystallization textures formed in the two steels is explained by the difference in the preferred nucleation sites and in the local crystal rotations in the vicinity of grain boundaries.