Papers by Keyword: Weathering Steel

Abstract: This article deals with the topic of atmospheric corrosion. Atmospheric corrosion causes damage to nearly 80% of all existing steel structures. The main parameters of atmospheric corrosion are the time of wetness (TOW), air temperature and aggressive corrosive agents such as chlorides, sulfur dioxide and others. Currently, low alloy steels with improved atmospheric corrosion resistance called weathering steels are used for the steel structures located in outdoor environment. A protective layer of corrosion products is created on the steel surface and this layer can reduce continuation of corrosion of steel. The time of wetness together with the effect of aggressive corrosive agents are various for surfaces oriented vertically or horizontally. Experimental tests of atmospheric weathering steel were carried out to monitor the impact of location and position of surface on the different constructions. These tests allow monitoring the development of corrosion products in real exposures. The article presents a part of the research, which includes monitoring the development of the thickness of corrosion products with regard to the position on the structure. Research is developed to refine of prediction models with the aim of improving determination of corrosion losses during the service life of the structure. Second part of these experiments is dedicated to measuring the deposition rate of chlorides. Chlorides have a corrosive impact on the steel surface. Under normal conditions the chlorides does not create suitable environment for the development of a protective layer of corrosion products.

Abstract: Complete the composition design and laboratory smelting of high strength weathering steel for railway freight car body of grade 500MPa. The actual continuous cooling transformation curve (CCT curve and cold speed of 0.5-50 °C/s) was measured through the Gleeble3500 thermal simulation test machine with expansion method and alloy phase method, observing the microstructures by optical microscope and SEM. The hardness of the samples under different cooling rates were measured by Vivtorinox hardness tester. Study on the effect of cooling rates on the microstructures and hardness of the steels.

Abstract: In this paper, the mechanical properties of Q355NH resistant steel welded joints are studied. Through the analysis of mechanical properties of welded joints, the results showed that the tensile strength of the welded joints decreased after annealing and the elongation increased. The impact test results of tensile specimens before and after annealing showed that the impact energy of the weld area increased greatly after annealing, while the impact energy of the heat affected zone changed little. Furtherly, fatigue strength of specimens before and after annealing was compared, and the results showed that under the condition of high cycle fatigue, the un-annealed specimens were broken and the fracture position was located on the parent metal, whereas the annealed specimens did not break.

Abstract: Continuous cooling transformation (CCT) diagram of a high strength weathering prefabricated building steel was determined using a DIL805L thermal dilatometer by means of the expansion method combined with metallography hardness method. Effect of cooling rate on microstructure and hardness of the steel was also studied. The results show that the austenite transformation products of the steel are ferrite and pearlite when cooling rate is lower than 3°C/s. In the cooling rate range of 3 to 20°C/s, the mixed microstructure of ferrite, pearlite and bainite can be obtained. When cooling rate is higher than 20°C/s but lower than 100°C/s, the microstructure is composed of ferrite, bainite and martensite. When cooling rate is above 100°C/s, ferrite disappeared completely, and transformation products are bainite and martensite.

Abstract: Resistance spot welding is widely used in automobile and rail car manufacturing industries. In this research work, resistance spot welded dissimilar joints of ferritic stainless steel and weathering steel sheets is investigated for mechanical and metallurgical properties. Ferritic stainless steel AISI 409M and weathering steel corten A (ASTM A 242) of 2mm thickness were used in this work. Spot welding was done at different current values, keeping other parameters such as electrode force, electrode tip diameter and weld time as constant. Test specimens were subjected to tensile shear test and micro hardness test to assess the mechanical properties of the weld joints. The influence of welding current on nugget growth, fusion zone hardness, peak load, and failure energy and failure mode during tensile shear test, was investigated at various current ratings. The results showed that, with increasing value of current, peak load increased correspondingly. Nugget shape was found to be near symmetrical. Nugget diameter was found to be increasing with increase in current, in expulsion free welds. Interfacial mode of failure was noticed at low current values, whereas, at higher current values, pull out mode of failure was observed. Presence of martensite was observed in the fusion zone. Micro hardness values at fusion zone were found to be more than that of both heat affected zones and base metals.

Abstract: Based on the 355MPa high weather-resistant steel, three different kinds of high weather-resistant steels were designed by varying the content of Ni. The the corrosion resistance of the high weather-resistant steel as well as the influence of Ni content on the corrosion resistance were studied in the present investigation. The results of the cycle corrosion tests indicated that with the addition of Ni, the corrosion resistance was improved to some extent. The rust layer of the weathering steel was composed of α-FeOOH and γ-FeOOH at the beginning of corrosion, and the α-FeOOH turned to γ-FeOOH which enhanced the corrosion resistance.

Abstract: The paper introduces the experimental corrosion tests that are carried out on the existing weathering steel bridges in the Czech Republic. The influence of the position and location of the surface in the structure on the resulting corrosion rates can be evaluated using this experimental testing. Typical surfaces of steel bridges are tested, e.g. webs of main girders, upper and lower surfaces of flanges, surfaces affected by leaking salt solutions. The corrosion tests to study the relation between steel grade (weathering steels S355J2WP and S355J2W) and corrosion rates are introduced in this paper as well.

Abstract: The paper describes the basic attributes of the new developed analytical method used for the calculation of corrosion losses on structural elements designed from weathering steels. The calculation takes into account the locality of the structure, type of the weathering steel, position and location of a surface in the structure and compliance with structural and maintenance requirements. The methodology for experimental testing of the realistic corrosion rates is introduced in this paper as well.

Abstract: Corrosion behavior of a low alloy steel A with 3% nickel content was studied by a wet/dry cyclic test. A commercial weathering steel Q450NR1 was used for comparison. The classical weight loss method was used to evaluate the weatherability of weathering steel, while the iron rust layers formed on weathering steel were analyzed by using SEM, XRD and electrochemical measurements. The results indicated that the corrosion resistance of steels A was better than that of commercial weathering steel Q450NR1 in the wet/dry cyclic test. The addition of Ni promoted the formation of α-FeOOH so as to improve the resistance of the rust. The EIS results indicated that the charge transfer resistance of steel A was bigger than that of steel Q450NR1.

Abstract: Weathering structural steel has been used for various outdoor load-carrying structures (even without anti-corrosion surface protection) in the world as well as in the Czech Republic for about 45 years [1, 2, 3]. Load-carrying structures are designed for service life of as many as 100 years and the weathering steel can be used as a standard structural material without any corrosion protection. The weathering steel is able to create a protective patina layer on the surface in favourable environment; it means suitable atmospheric and structural conditions. A lot of constructions built from the weathering steel in the Czech Republic have been assessed and inspected in last few years. This paper describes the new developed method for experimental measuring of real corrosion losses on typical surfaces of bridges.