High Tensile Structural Steel Research Articles

Corrosion failure analysis of a railway tanker containing concentrated sulfuric acid

In this paper, the authors carried out a corrosion failure analysis of a railway tanker containing 92.5% sulfuric acid, in order to investigate the cause of the leakage accident that occurred in 2016 and to provide a theoretical basis for preventing similar accidents. The morphology and chemical composition of the corrosion scale were characterized by SEM and EDS. The theoretical corrosion rate of the railway tanker was calculated using weight loss experiments. The corrosion behavior model was established by electrochemical experiments. In order to investigate the cause of this leakage, a mechanical model was established, and the force of the railway tanker during transportation was analyzed through ANSYS software. The results show that the tanker material (low-alloy high-tensile structural steel, Q295A) meets the quality standard, and the main cause of this leakage accident was the local corrosion failure of the tanker leading to a crack due to stress during the transportation process. The corrosion source is diluted H2SO4 solution. The main component of the corrosion scale was Fe2O3. The theoretical corrosion rate was in the range of 1.413–1.978 mm/a, and the corrosion rate increased with the decrease in the concentration of H2SO4. The corrosion type was pitting corrosion. When the brake is applied when the tanker is in full load, the stress inside the tanker is about 8.94 times higher compared to a tanker with empty load in the static state. Because of this uneven force, a crack may develop leading to leakage from the corroded area of the tanker.

Experimental Investigation of DSS/HRS GTAW Weldments

Objectives: The Gas Tungsten Arc Welding (GTAW) of blanks 2 mm thick of Duplex Stainless Steel (DSS) and Hot Rolled Medium and High Tensile Structural Steel (HRS) is carried out to investigate the metallurgical, mechanical properties and the fracture. Methods: The characterization of the weldments involves tests, viz. macrostructure, microstructure, micro composition analysis through Energy Dispersive Analysis of X ray (EDAX) to find out the metallurgical properties and micro hardness test, tensile test, bend test to determine the mechanical properties of the weldments. Topography of tensile test fractured specimens was analyzed with the help of Scanning Electron Microscope (SEM) and determines the influence of the welding on the ductility of the weld material. Findings: The increase in the weld zone micro hardness and formation of dendritic delta ferrite microstructure, when compared with the DSS parent metal having elongated grained austenite with ferrite and the HRS parent metal having fine grains of ferrite, caused the joint efficiency of the DSS/HRS weldment to increase. The Energy Dispersive Analysis of X ray (EDAX) indicates the formation of dendritic delta ferrite microstructure is attributed to the presence of elements like Si and Cr. The SEM fractography analysis indicates that the weldments possess good tensile strength without decrease in ductility of the fusion zone. Applications: Experimental investigation of mechanical properties and microstructure of DSS-HRS dissimilar GTAW weld joints and fracture analysis with EDAX to identify the changes in the chemical compositions of the fractured specimen.

Mechanical properties of heat-treated high tensile structural steel at elevated temperatures

This paper investigates experimentally the mechanical properties of heat-treated high tensile strength low alloy structural steel RQT 701 with proof strength of 740MPa at elevated temperatures. Standard axial tensile tests at elevated temperatures were carried out by using both steady-state and transient-state methods. The test results were compared with those from mild steels of grades up to S460. The comparisons indicate that the RQT 701 steel has smaller relative thermal elongation, and higher reductions of effective yield strength and elastic modulus at elevated temperatures. The test results on proportional limit, effective yield strength and elastic modulus were fitted into Eurocode stress–strain models for numerical analysis and fire resistant design.

我が国における溶接構造用高張力鋼の発展とその特徴

我が国における溶接構造用高張力鋼の発展とその特徴

Fatigue Strength of High Tensile Structural Steels and Welded Joint

Fatigue tests on plain and notched specimens, specimens with mill scale and welded joint of 40∼100 kg/mm2 various structural steels under different stress conditions were carried out. Relations between fatigue limits and tensile properties of the base metal were investigated. Slope of S/N diagrams and number of cycles at knee point, in relation to tensile strength and stress concentration factor of notch, were discussed. The influence of oxidation of weldable steels on the fatigue limit, and the fatigue strength of welded joint in various steels were also examined.

Fatigue Strength of High Tensile Structural Steel and Welded Joint

Fatigue Strength of High Tensile Structural Steel and Welded Joint

構造用高張力鋼継手の疲労強度

構造用高張力鋼継手の疲労強度

有孔切欠試片による衝撃曲げ試験

The object of this paper is to study the breaking behaviours of a structural steel for low temperature service in Charpy impact bending test using the perforated notched test pieces which were proposed by one of the authors.The results obtained in this paper are summarized as follows:(1) The perforated notched test piece is available for the differentiation between the crack initiation and propagation stages. The crack initiation energy can be estimated easily by using the both of the perforated notched test piece and the standard key hole test piece.By this method, the relationship between the breaking energy and the breaking length in brittle fracture can be also determined. This relationship indicates a distinct difference between the test steel and the high tensile structural steel already tested.(2) The impact tensile strength can be calculated from the maximum load of load-time curve which has been obtained at the breaking of perforated notched test piece in Charpy bending test. The calculated values of impact tensile strength are about 1.1∼1.4 times of the values of upper yield strength obtained by the high speed tension test under the stress rate 4×106 kg/mm2·sec which is equal to the stress rate of Charpy bending test.

H.T.60の試作研究結果について(第3報)

Based on the rusults of the investigation reported in the 2nd report, four heats of the Vanity+Ni +Cr+Mo type as the high tensile structural steel with tensile strength over 60kg/mm2 (H.T. 60) were melted in the 20 ton electric basic furnace, and their mechnical properties and weldability were examined in detail.1. It is needed for getting satisfactory results that carbon content is kept about 0.13 and 0.15% for as rolled and normarized plates, respectively. Otherwise materials show much less tensile strenght or less elongation. Other alloying elements must be lowered to guarantee weldability of plates.2. All steels tested are warranted for V-notch Charpy test results.3. From the view points of hardenability and crack sensitivity, it is recommended that the respective Ceq are lower than 0.45 and 0.35.4. Maximum hardeness below 350Hv in H.A.Z. of I.I.W. test guarantees the resistance to the generation of crack of Kinzel and Kommerel tests, and the I.I.W. maximum hardness plus the hardness of parent metal as low as possible under 550Hv guarantees no breaking at the bending angle of 120 dergee of Kommerel test.

H. T. 60の試作研究結果について(第2報)

Based on the rusults of the investigation reported in the 2nd report, four heats of the Vanity+Ni +Cr+Mo type as the high tensile structural steel with tensile strength over 60kg/mm2 (H.T. 60) were melted in the 20 ton electric basic furnace, and their mechnical properties and weldability were examined in detail.1. It is needed for getting satisfactory results that carbon content is kept about 0.13 and 0.15% for as rolled and normarized plates, respectively. Otherwise materials show much less tensile strenght or less elongation. Other alloying elements must be lowered to guarantee weldability of plates.2. All steels tested are warranted for V-notch Charpy test results.3. From the view points of hardenability and crack sensitivity, it is recommended that the respective Ceq are lower than 0.45 and 0.35.4. Maximum hardeness below 350Hv in H.A.Z. of I.I.W. test guarantees the resistance to the generation of crack of Kinzel and Kommerel tests, and the I.I.W. maximum hardness plus the hardness of parent metal as low as possible under 550Hv guarantees no breaking at the bending angle of 120 dergee of Kommerel test.

熔接構造用HT60に関する研究

This paper reports the investigation of weldable high tensile structural steels, having 60-70kg/mm2 tensile strength, with a satisfactory notch toughness and weldability. The main conclusions are obtai-ned as follows;(1) In the present results upon the effects of alloying elements for Mn-V type steel, comparatively satisfying results are obtained for Modifyed Vanity Type Steel, contain about 0.5% Ni.(2) Concerning the range of chemical composition of commercial steel, it is difficult to satisfy both the high tensile strength and lower Maximum Hardness of Heat-Affected zone.(3) High Tensile, High Notch-Tough Steel, ("2H" Steel) obtained after special heattreatment has a tensile strength over 60kg/mm2 and higher yield ratio of 85% and excellent notch-toughness and weIdability as shown in table 4. Therefore this "2H" Steel is the most practical steel for use welding construction.

H.T 60の試作研究結果について(第1報)

As the first step of producing high tensile structural steels (H. T. 60) with tensile strength over 60 kg/mm2 and good weldability, five laboratory heats prepared by adding Ni, Cr, Mo, V and Ti, to the Si+Mn type usually adopted for making a high tensile steel with tensile strength below 60 kg/mm2 were melted and tested. From this experiment it is deduced that by decreasing C and Mn contents and adding V and Ti, the ductility transition temperature and the maximum hardness in H. A. Z. can be lowered, keeping tensile strength above 60 kg/mm2. But the plates as rolled would be attended with the danger that elongation may not be high enough and ductility transition temperature lowered. In case of normalizing plates, however, the tensile strength will be lowered and the ductility can be considerably improved. And it is learned that replacing Mo with V and Ti, better weldability can be achieved as H. T. 60 plates.

構造用高張力鋼板の試作研究

Four kinds of high-tensile structural steel sheets of Mn-series, Cr-series; and Moseries, each of which contains small quantity of the corresponding element, were manufactured experimentally and studied with reference to the melting, working efficiency in rolling and properties of the sheet. The specimens of the following analyses were taken from the sheet of 12mm. thickness whi.ch had been rolled from the ingot each weighing 7, 500kg and being made by the basic electric furnace.No difficulty was met with in melting and rolling. The properties of the sheet as rolled fall in the range: tensile strength 55-65kg/mmmm2, yield point 40-45kg/mmmm2, and elongation 20%. When various analyses were compared, they showed negligible difference in mechanical properties either as rolled or as simply heat-treated; but the single-Mn series steels which are currently used were proved to be economical and practical; and, when subjected to a further heat treatment such as quenching and tempering, the Gr-and Mo- series proved to be slightly better.

Observations on the Arc Welding and Gas Cutting of High-Tensile Low-Alloy Structural Steels

High-tensile structural steels generally contain relatively small additions of alloying elements which affect their welding properties because of hardening effects. The paper gives data regarding the composition and test values of some typical high-tensile steels, together with results on metallic-arc welded joints. Laboratory cracking tests to determine the weldability of steel plate are described, and their utility is demonstrated. The composition and inherent grain size of the steel, together with the conditions of welding, affect the properties of the heat-transformed zone. It is desirable to limit the carbon content to 0·20 per cent; and for single-run fillets the use of a relatively slow welding speed of 4–6 inches per minute, with a fillet size of not less than half the thickness of the plate, has given the best results in the authors' work. The properties of various covered electrodes have been studied. Carburization experiments on all-weld metal reveal interesting differences between electrodes. The cutting of these steels by gas is considered, in so far as most of the factors influencing weld hardness may operate, to produce cut edges having hard surfaces of reduced ductility.