1、 外文资料翻译 WELDABILITY ANALYSIS OF Q345 STEEL LOW STEEL ALLOY STRUCTURE OFWELDABILITY ANALYSIS 16Mn 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 weld
2、ing, 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 cont
3、ent 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 i
4、s 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 de
5、pends 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 higher than some, so this low carbon steel hardened tend to be bigger than that, but with the increase of steel strength level, the
6、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-heat temperature, to control the heat-affected zone of the cooling rate, while reducing the amount of weld metal hydrogen
7、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 suc
8、h 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 r
9、ole 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
10、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
11、 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 ST
12、RUCTURAL STEEL WELDING 1. 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 reduce the consumption of welding materi
13、als . (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, rus
14、t, 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 a
15、nd 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 n
16、ot 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. Preheati
17、ng, 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: Change in welding heat
18、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； Reduce the welding area Wendu gradient, reducing the stress of welded joints, and make it a more even distribution； To 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；
