鋼材の熔接諸条件と冷却時間(第2報)

Authors have made a study of the effect of the thicker plates urged by the need to solve the following constructional problem of 45, 000 DWT ore and oil carrier which our yard is planning of build.The construction of this ship as it is shown in the Fig. 1-Midship section, there is a large opening in the centre of upper deck. In this case, in way of supporting upper deck sectional area, there arose a question whether we shall adopt the doubling system which is usually applied to ore carrier, or boldly do away with the doubling plate and use extra thick plate instead. To be more in detail, if (a) two lines of doubling plates were passed on one side the plate thickness of upper deck would be sufficient by being 38 mm, but if (b) the doubling plates were limited to a single line then the thickness of plates requires to be 40mm and in case of (c) no doubler the thickness must be 47 mm.In consideration of the work in the spot, the compensation by the doubling involves a diffecult job. On the other hand, in consideration of the quality of steel and its weldability it seems more undesirable as the thickness of the steel plates become larger. As far as the thickness of the plates is concerned, there is not much difference in the effect 'between 38mm and 40 mm, so our consideration of the problem was focussed to whick should we choose, (b) or (c).The steel to be used for the purpose which came to our mind was C class steel of AB Rule, but when the thickness of steel becomes so large it is questionable whether we many obtain a suitable material that comes within the specifications of C class steel and a satisfactory joinability of the same time. So with a view to find out which possesses better joinability and the weldability for service, we made the following tests in order to make a comparative study between (b) and (c).1. Tension Test in room temperature.2. Standard V-Charpy Impact Test in the range of temperature -40°C to +60°C.3. Longitudinal Bead Bending Test (Kommerell Test) in the rang of temperature -60°C to +40°C.From these tests we could reach to the following conclusions.(1) According to the static tension test of both plates, of cf .Fig. 4, the normalizing will increase both yield strength and elongation, but gives hardly any effect to the tensile strength. (cf Fig. 5)(2) In the V-Charpy test, cf Fig. 6, the normalizing will lower 40 ft-1b transition temperature of the steel of both plates, but there was not hardly notceable of the effect to 15 ft-1b transition temperature. (cf Fig. 9) Generally 47mm thick plates, in comparison with 40mm thick plates, the notch sensitivity is somewhat larger, but the impact value in low temperature was sufficiently large when normalized. (cf Table 3 and Figs 7-13)(3) In the Kommerell test, cf Figs 14 and 27, both plates showed much larger bending angle than what is required under Austrian Welding Standard (cf Fig. 27). (cf Fig. 28). When low hydrogen electrode was used, the toughness of the weldments was very high, and even when the other types of electrode were used, if weldment was preheated it regained its toughness very noticeably. (cf Figs. 22-26)

Dissimilar metal welding was mostly done to optimize the application and engineering requirements with economic considerations. Weld microstructures greatly influenced the mechanical properties of welded joints. The investigations were carried out to evaluate the microstructural and mechanical properties of dissimilar weldment between carbon steel ASTM A36 and austenitic stainless steel 304 with a variation of welding position (1G, 2G, 3G) and weld thickness (6 mm to 12 mm) joints by TIG welding. A detailed analysis was conducted on the weld zone composition, the microstructural, and mechanical properties. The results show that the welding position and thickness of the weld joints influenced the microstructure both in HAZ and weld metal. Size, distribution, and orientation of microstructure were improved and more uniform with increasing of welded joint thickness. In HAZ carbon steel, GB ferrite was dominant, especially for the flat welding position (1G), while for the horizontal position (2G) and the vertical welding position (3G) showed other structures such as Widmanstaten ferrite, hard-structures like martensite and bainite. In the region near the fusion line and the weld metal, the chemical composition changed due to thermal convection, diffusion, and macro-segregation caused by penetration of liquid metal carbon steel into the weld pool. SEM/EDS results indicated diffusion of carbon from carbon steel A36 to stainless steel 304 and formed the hard-structure along the fusion line. The mechanical test results showed that the tensile test breaking point occurred in the parent metal of carbon steel A36. The bending test results showed very high stress on the face side of the welding joint, and there are no cracks from the bending test result. Vickers hardness testing showed that the hardness distribution increased from the carbon steel HAZ to the stainless steel HAZ, and the maximum hardness has achieved the value of 297 Hv at the fusion line of stainless steel 304.

In order to meet the development needs of deep-sea oil and gas resources, deep-sea corrosion coupon tests were carried out in the South China Sea, the Western Pacific Ocean, and the Indian Ocean, which can provide a strong guarantee for the rationality of material selection of oil and gas pipelines, platforms and other facilities. In-depth studies were conducted on the environmental adaptability of typical carbon steel and low alloy steel materials after exposure for one year in the deep-sea environment of different sea areas. The main environmental factors affecting deep-sea corrosion behavior were also collected and analyzed. The results showed that the corrosion morphology of carbon steel and low alloy steel in deep sea environment was more uniform than that in the shallow seawater. With the increase of seawater depth, the evolution law of their corrosion rates in different sea areas was similar, with an obvious decline of corrosion rate in the beginning. The gray correlation results indicated that it was mainly controlled by temperature and dissolved oxygen. The high hydrostatic pressure had limited effect on accelerating the deep sea corrosion rate of carbon steel and low alloy steel, but it promoted the formation of more uniform corrosion morphology.

The dissimilar steel joints of austenitic stainless steel and low alloy steel are commonly used in superheaters and super heaters of the boiler. Carbon migration is an important factor affecting the life of welding joints during service. In this paper, the carbon migration of T23 and TP304h dissimilar steel of welding joints was studied. The results show that carbon-rich zone and carbon-depleted zone are formed near the interface between the T23 bases and weld metal. The carbon-rich zone is located near the weld line in weld metal. On the other hand, the carbon-depleted zone is located at the T23 steel base metal. Significant carbon migration phenomenon can be observed by the optical micrographs of the welding joins. The morphology of the carbon-rich zone along the fusion line can be used as a “feather” for identification and extends toward the center of the welding joints. In the carbon-depleted zone, it is found that the microstructure of the carbon-depleted zone near the fusion line is inhomogeneous and relatively coarser, and the micro hardness of the carbon-rich zone is significantly different from that of the surrounding zone. The carbon-poor zone is becoming a weak link to promote the process of crack propagation.

A comprehensive study of fluidized bed nitriding was performance on a carbon steel (grade AISI St 41) and low alloy steel (grade AISI 4140) at 550 0C in 20 % N2 and 80 % NH3 atmosphere at a flow rate gasses of 0.7 m3/hr. Various surface roughness were used to incorporate nitrogen into these steels. The nitride layer formed at AISI 4140 showed better surface roughness and surface hardness than AISI St 41. With low chromium alloy (grade AISI 4140), nitrogen diffusion is more uniform in the lower surface roughness after nitriding process. It has been found that the surface microhardness of the compound layer increases with decreasing surface roughness and chromium alloy contents. The layer nitride has a decrease surface roughness ranging from 50 % at 0,1 µm to about 17 % at 0,5 µm. On the contrary, the carbon steel without chromium alloy (grade AISI St 41) sample show an enhance surface roughness between 1.3 to 2.5 times after nitriding process, but on 0.5 µm surface roughness sample show a decrease surface roughness of about 10%. All sample show an enhanced surface microhardness after nitriding significantly. Chromium alloy is found to enhanced the nitriding efficiency. Without chromium in the steel, a lower surface roughness provides a supplementary amount of implanted nitrogen available for further diffusion, and the uniform of the surface passive oxide. So, with limited surface roughness, more uniform layers with higher amounts of nitrogen can be achieved by low chromium alloy. However, with limited solubility of nitrogen atom in α-Fe into iron nitride form, the nitrogen becomes supersaturated reaction and nitride layer is more brittle and porosity. It is can be ascribed to the nitrogen solubility in the nitride layer, which at AISI St 41 is higher due to the formation of porosity phase while at AISI 4140 a phase rich in nitrogen (ϒand e phases) is formed.

AbstractExamination of ferrules used to control the flow of water at 300°C through individual tubes in an evaporator unit has shown that carbon steels can undergo high rates of erosion–corrosion (up to 3mm/year) under these conditions. It is concluded that such high rates of erosion–corrosion are due to the exceptionally low level of chromium in the steel and a very high mass transfer coefficientfor soluble iron at the surface. For levels of chromium up to 2·3% in carbon and low alloy steels, resistance to erosion–corrosion appears to be directly proportional to the level of chromium in the steel. The absence of any enrichment of molybdenum or copper in the oxide layer indicates that the presence of these elements is unlikely to enhance resistance to erosion–corrosion inflowing water. A simple hydrodynamic model is proposed to account for observed variations in surface condition and rate of erosion–corrosion within the ferrules.

Microstructure and Stress Corrosion Cracking of Dissimilar Metal Weld 16MND5/309L/308L/Z2CND18-12N Used for Connecting Reactor Pressure Vessel to Piping in Nuclear Power Plants

Soviet reference materials for ferrous metallurgy

An investigation was carried out to establish the suitability and performance of candidate corrosion inhibitor packages for downhole production applications. The study covered both H2S and CO2 corrosion performance of carbon steel and low alloy steel tubulars in simulated West Kuwait oil field conditions. The performance of the corrosion inhibitors was established through the use of a number of inhibitor selection methods by systematic determination of efficiency, persistency and chemical compatibility of both corrosion and combined corrosion/scale inhibitor packages. The results have led to the determination of effective means of corrosion mitigation to enable wider uses of carbon and low alloy steels for downhole applications. Introduction Corrosion has wide ranging implications on the integrity of Materials used in the Petroleum Production industry. It manifests itself in several forms amongst which CO2 corrosion (sweet corrosion) and H2S corrosion (sour corrosion) are by far the most prevalent form of attack encountered in oil and gas production. The implication of these types of attack can be viewed in terms of their effects on both capital and operational expenditures and health, safety and the environment (HSE). Increasing water production gives rise to these types of attack and potential corrosion of carbon and low alloy steels in the presence of acidic gases (1–3). One means of corrosion control is through the use of effective inhibitor packages. Subject to continuous and sufficient availability, corrosion inhibitors can offer adequate corrosion mitigation against the risk of CO2 corrosion for the safe and trouble free application of carbon and low alloy steel production tubulars. This study dealt with the evaluation of corrosion performance of candidate tubular steels in the absence and presence of a selected number of inhibitor packages recommended by chemical suppliers. The environmental conditions represented those of west Kuwait downhole production conditions and tubulars were according to API 5 CT grades L80 and C90 carbon and low alloy steel. Experimental Methods Test Materials Two grades of carbon steel tubular were used throughout the test program. These alloys are API 5CT grade L80 and C90 type I. Both steels were Cr-Mo-B-Ti modified offering improved SSC resistance. The elemental analysis and mechanical properties of these two grades of steel are shown in Table 1and 2. Coupons were mechined from grades L80 and C90 tubulars and were sandblasted prior to testing. They were then degreased using acetone, dried and stored in discators prior to testing. After each test, the coupons were cleaned and degreased by rinsing in 15% hydrochloric acid followed by rinsing in sodium carbonate and distilled water, then rinsed with acetone and dried. Inhibitor Packages Three inhibitors package were obtained from three chemical companies. The recommended chemicals were based on water chemistry and production conditions and are described in Table 3. Wheel Test Wheel testing was carried out in accordance with industry practice to determine corrosion rate of exposed samples in semi-static conditions in the presence of candidate inhibitor packages over a 96-hour period. The test was intended to rank inhibitors chemicals. The samples were examined subsequently by means of weight loss and visual observations. Data were generated in the absence of corrosion inhibitors to determine the actual corrosion rate both in the absence and presence of crude oil. Among the chemical packages, two best performing chemicals were selected for further electrochemical evaluations. Test Materials Two grades of carbon steel tubular were used throughout the test program. These alloys are API 5CT grade L80 and C90 type I. Both steels were Cr-Mo-B-Ti modified offering improved SSC resistance. The elemental analysis and mechanical properties of these two grades of steel are shown in Table 1and 2. Coupons were mechined from grades L80 and C90 tubulars and were sandblasted prior to testing. They were then degreased using acetone, dried and stored in discators prior to testing. After each test, the coupons were cleaned and degreased by rinsing in 15% hydrochloric acid followed by rinsing in sodium carbonate and distilled water, then rinsed with acetone and dried.

This chapter covers the basics of weldability of cast steels such as carbon and low alloy steels, corrosion-resistant high alloy steels, nickel-base alloys, heat-resistant high alloy steels, and wear-resistant high austenitic manganese steels. It provides an overview of weld overlay and hard facing; cast-weld construction; and plasma arc cutting and plasma arc welding. The chapter discusses different types of welding processes. These include shielded metal-arc welding, air carbon arc cutting process, gas tungsten-arc welding, gas metal-arc welding process, flux-cored arc welding, submerged arc welding, and electroslag and electro-gas welding.

This chapter defines low-temperature and cryogenic steels and describes their alloy classifications and their ambient and low-temperature properties. These steels include ferritic carbon and low alloy steels, martensitic low alloy steels, martensitic high alloy steels, and austenitic high alloy steels.

Abstracts: Metals: Non-Ferrous; Ferrous; Pure Iron; Simple Alloys; Carbon Steels, Cast Iron; Low-Alloy Steels; High-Alloy Steels

Principles of the Heat Treatment of Plain Carbon and Low Alloy Steels provides readers with a working knowledge of heat treat processes and how they can be tailored to optimize the microstructure and properties of steel. The book includes chapters on quenching, tempering, austenitization, and annealing as well as hardenability, modeling, and common treatments for structural steels. The first few chapters lay essential groundwork for understanding how time, temperature, and prior processing history influence the formation of Fe-C phases and the composition and morphology of the microconstituents found in carbon and low alloy steels. The chapter on structural steels explains how deformation and thermal processing are used for the development and control of grain size and how carbon and manganese content influence toughness, hardness, and strength. The final chapter presents worked solutions to real-world problems related to hardenability, quenching, grain size, alloy content, treatment times and temperatures, and the determination of property ranges. The book includes an extensive amount of composition and property data, a glossary of terms, and outlines for various calculation methods. For information on the print version, ISBN 978-0-87170-538-9, follow this link.

Characterization of fusion boundary between low alloy steel and stainless steel cladding

Additive manufacturing (AM) technology can potentially disrupt offshore and marine industry by effectively reducing manufacturing processes and leadtime, and enabling new product designs. A review of existing literature has revealed limited knowledge in using AM to process shipbuilding materials, which can otherwise enhance existing shipbuilding manufacturing workflow. This has led to the research motivation to establish the technical feasibility of using selective laser melting (SLM) to process ASTM A131 EH36 shipbuilding steel. SLM process is a widely understood AM technology that has been used extensively to process other type of steels, for example stainless steel 316L. EH36 belongs to a class of high tensile low alloy steel which has traditionally been processed through casting. However, knowledge on using lasers to process EH36 is largely unknown, especially in AM applications. Using SLM to process EH36 is novel and will solve the problem of lack of knowledge in this field. The study thus aims to further the understanding of the mechanical properties and microstructure of SLM processed EH36. A preliminary investigation was first carried out to establish the technical feasibility of using SLM to process EH36. The process parameters obtained were then used to further the investigations. Heat treatment process was applied as a possible post processing technique. Mechanical testing was carried out to characterise its mechanical properties. The fracture surfaces and microstructures were then studied to characterise the material. The results showed that EH36 can be processed using SLM without any visible cracks. The mechanical properties of as built SLM processed EH36 exhibit very high tensile strength, but low ductility. The ductility can be improved through tempering heat treatment process, but at the partial sacrifice of tensile strength. Fractography analysis also affirmed the lack of ductility in the SLM processed EH36 samples. Finally, the microstructure showed that fine grain size and martensitic microstructure were the primary drivers behind its high tensile strength. Tempered samples experience grain coarsening and phase transformation to a mainly ferritic structure, which led to recovery in its ductility but a decrease in the tensile strength. A scaled model was fabricated to validate the results from the microstructure studies, and the findings indicate similar microstructures formed. This demonstrates the repeatability of the developed process parameters on fabrication of complex joints. The study contributes to the scientific knowledge with regard to material and mechanical property characterisation of SLM processed EH36. The findings from the fractography and microstructural analysis will contribute towards building the knowledge and facilitate future work on AM of EH36.