外文资料翻译WELDABILITY ANALYSIS OF Q345 STEELLOW STEEL ALLOY STRUCTURE OF WELDABILITYANALYSIS16Mn and 15MnV belong to the low-alloy steel hot rolled steel, these steel prices lower, and has satisfied the mechanical properties and processing performance, first of all to analyze this type of steel welding, welding on two points of typically Bianxian questions: First, due to a variety of welding defects, such types of steel for the main crack; Second, changes in material properties when welding on the type of steel is mainly embrittlement problem.1. Crack(1) Thermal crack: hot rolled carbon content generally lower, while the higher manganese content, so they Mn / S comparison, and has good resistance to thermal cracking performance. Normally, the weld hot cracking does not occur, but when the material component failure or serious segregation of carbon, sulfur content higher, Mn / S ratio is low, prone to hot cracking. Manganese in the steel with manganese sulfide sulfur to reduce the harmful effects of sulfur and enhance the performance of steel thermal cracking.(2) Cold crack: the crack depends on the cold steel, hardened steel, the tendency of the tendency toward hardening just depends on its chemical composition. Hot rolled steel contains a small amount of alloying elements because of its low carbon steel when the carbon equivalent is slightly high er than some, so this low carbon steel hardened tend to be bigger than that, but with the increase of steel strength level, the increase in alloying elements, it The hardening tendency increases should be based on the form and steel fittings to adjust the line thickness of the energy, preheating and post-heattemperature, to control the heat-affected zone of the cooling rate, while reducing the amount of weld metal hydrogen and other measures to prevent cold cracks.(3)Reheat cracking: Considerations from the chemical composition of steel, hot rolled steel does not contain as strong carbide forming elements, so again not sensitive to hot cracking, but also by increasing the preheating temperature and post weld heat such measures immediately after to prevent hot cracking.2. Embrittled(1)Hot zone embrittlement: hot rolled steel welding near the weld zone is heated to above 100 ℃coarse grain zone, easy to produce grain growth phenomenon is worst in welded joints of plastic parts, often to withstand the stress the role of the damage. To prevent the overheating zone embrittlement measures is to improve the cooling rate, in particular, to improve the stability of austenite within the minimum cooling rate, shorten the residence time in this temperature range, reduce or prevent the emergence of austenite to raise steel impact toughness, but also to prevent the overheating zone coarse-grained brittle, should not be using too much energy input.(2) Heat should be crisp: the heat should be crisp is the thermal stress during the welding process because the plastic deformation to dislocation multiplication, while nitrogen and carbon atoms induced rapid proliferation of dislocation accumulation area, there should be crisp of heat. 16Mn and 15MnV these two types of steel has got to be brittle tendency of heat, eliminating welding heat should be crisp and effective measures of post-weld annealing.LOW ALLOY STRUCTURAL STEEL WELDING1. Welding preparation:(1) The design of groove type of welding should be avoided not through or partial penetration of the groove, but also to minimize the weld cross-sectional area to reduce the residual stress in joints, it can also reducethe consumption of welding materials .(2) Groove to note when using thermal cutting edge of the base metal will prevent the formation of a certain depth of the hardened layer, this hardened layer of low ductility often cold cracking source.(3) Weld area before welding steel to eliminate surface moisture, groove surface oxide, rust, grease and other contaminants.(4)Before use welding materials manufacturer recommended specifications should be dry.(5)Orientation and assembly, and the formal weld seam must be the same type of electrode.2. Welding heat input of choice:Line energy parameters is welding current, arc voltage and welding speed. Low-alloy structural steel welding, heat input parameters to the need to ensure that joint penetration and weld, but also consider their joint performance. Welding of low carbon content and carbon content of hot-rolled steel lower side of the 16Mn steel, the welding heat input is not strictly limited, but improve the plasticity and toughness of hot zone or consider the use of smaller line energy is more favorable; when welding with 16Mn high carbon steel, in order to reduce the hardening tendency, to prevent cold cracks, welding heat input is too large to be more.3. Preheating, heat and heat treatment after(1) Preheating: welding low alloy steels, preheat the cold when the joints to prevent cracking, to improve the performance of joints, reducing the welding stress the importance of technological measures. Preheat the beneficial effect also in: ①Change in welding heat cycle, reduce the high temperature transformation of various welded joints and low transition temperature of the cooling rate, to avoid or reduce the formation of hardened tissue; ②Reduce the welding area Wendu gradient, reducing the stress of welded joints, and make it a more even distribution; ③To expand the temperature field of welding area so that welded joints in a wide area in the plastic state, and has reduced the adverse effects of welding stress; ④Extension the welding area in more than 100℃of the residence time is beneficial in the escape of hydrogen from the weld metal. Preheat temperature to determine, with the carbon equivalent of steel, thickness, degree of structural constraint increases, the ambient temperature rises.(2)After the heat and heat treatment: after heat is the weldment after welding the end of the entire weld immediately heated to 150 ~ 250℃temperature range, and maintain a period of time, after such a process referred to as hot. Its role is to first reduce the joints at low temperature change of cooling rate, the more pronounced effect than warm, followed by the extension of the joint in more than 100℃range of residence time, so that the hydrogen in weld metal have sufficient time outside proliferation. Proliferation phase of metallic hydrogen in the wind, virtually eliminating lead from the cold crack formation of mechanical factors. After the hot temperature and time, depending on the welded steel cold cracking, welding materials, hydrogen content and degree of joint restraint. The higher the temperature after the heat, the longer the holding time, the more obvious effects dehydrogenase.Dehydroepiandrosterone treatment is welded immediately after the welding heat to 300 ~ 400℃and the heat for some time, could accelerate the spread of welded joints of hydrogen escape. The exclusion of hydrogen depends on temperature and time, high temperature holding time may be shorter, low temperature dehydrogenase time would lengthen. Eliminate the production of hydrogen treatment temperature of 300 ~ 400℃, hydrogen consumption for 1 to 2 hours.Elimination of stress treatment is welded evenly heated to a certain speed AC1 points below the temperature high enough, holding a period of time evenly with the furnace cooled to 300 ~ 400℃, the last piece moved to the furnace will be cooled. Low alloy steel after welding to eliminate the purpose of dealing with stress the following points: ①To eliminate the hydrogen in weld metal, to improve the crack resistance of welded joints and toughness;②Reduce the involvement of stress in the welded joints; ③Improve the weld metal and heat affected zone, so that organizations undergo tempering thehardened joint districts to improve the toughness; ④Stability of low-alloy heat resistant steel weld metal and heat affected zone of carbide, high temperature lasting increase joint strength; ⑤Reduced weld and heat affected zone hardness, easy cutting.Q345焊接性分析低合金结构钢的焊接性分析16Mn和15MnV均属于低合金结构钢中的热轧钢，这类钢价格便宜，而且具有满意的综合力学性能和加工工艺性能，首先来分析一下这类钢的焊接性，焊接性通常变现为两方面的问题：一是焊接引起的各种缺陷，对这类钢来说主要是各类裂纹问题；二是焊接时材料性能的变化，对这类钢来说主要是脆化问题。