焊接技术及其自动化毕业论文（Welding technology and automation graduation thesis）

1、焊接技术及其自动化毕业论文（Welding technology and automation graduation thesis）Welding technology and automation graduation thesis topic: low alloy steel T welding joint deformation, measurement and calculation: Department of materials science and engineering, material forming and control engineering, welding te

2、chnology and automation in welding heat input due to high concentration in the process of transient, in the process of the welding will inevitably produce welding the stress and deformation, and the welding deformation of the appearance of the structure, bearing capacity, service performance and oth

3、er aspects have many negative effects, so it has very important practical significance for analysis and estimation of welding residual deformation. Based on the T component as the research object, making unbeveled or groove welding procedure test, analysis of factors affecting the welding deformatio

4、n, especially in the process of welding heat input makes the key discussion; longitudinal shrinkage of T type welds are measured, calculating the deformation amount is calculated in. Based on the simplified science, and the estimated values are compared with the measured value. The experimental resu

5、lts show that the selected welding parameters in line with the actual welding requirements formula properly, the welding process and deformation calculation method can provide theoretical basis for the actual production. Keywords: T joint; welding deformation; Abstract Welding is a reliable heat inp

6、ut and effective method of material connecting so it is widelyapplied to various industries. The presence of residual deformation affects not only thestructure of the dimensional accuracy and appearance and may reduce its carryingcapacity and mechanical performance so welding distortion prediction a

7、nd control is veryimportant. With the computer and the development of finite element analysis computersimulation of mechanical behavior of the welding process to become an essential way theuse of inherent strain method to predict welding deformation is a typical example. In thispaper T-welded compon

8、ents for the study analysis and forecasting using the inherentstrain M Ethod T-welded components transverse contraction and longitudinal contraction.Focus on the inherent strain analysis method and computer application process werestudied.Key words: T-joint Welding distortion Heat input Introduction

9、. 1 chapter of welding deformation and its influencing factors. 31.1 welding deformation causes. 31.2 welding deformation and the classification of the association between. 41.3 welding deformation factors. 7 1.3.1 material factors. 7. Effects of 1.3.2 structural design factors. . 7 1.3.3 welding me

10、thods. 8 1.3.4 welding layers. 8 1.3.5 joint type. 8 1.3.6 weld cross-sectional area of welding deformation influence. 91.4. The prevention and control of welding deformation. The method. 9 1.4.2 间断焊接 . 10 1.4.3 减少不必要的焊道 . 11 1.4.4 反变形法 . 11 1.4.5 刚性固定法 . 11 1.4.6 锤击焊缝法 . 11第二章 T 型构件焊接工艺及焊接变形测试 . 12

11、 2.1 试件的材料及尺寸 . 12 2.2 材料的成分及性能 . 12 2.3 焊接工艺参数的选择 . 13 2.4 焊接步骤 . . 16 2.5 焊接变形的测量与结果 . 17第三章 变形的计算 . 17 3.1 焊接变形计算方法 . 17 3.1.1 解析法 . 18 3.1.2 热弹塑性有限元法 . 18 3.2 固有应变法 . 20 3.2.1 固有应变 . 20 3.2.2 固有应变法焊接变形的解析法 . 223.3 试件焊接变形的计算 . 233.4 The calculated and measured is compared. 233.5 experimental anal

12、ysis of causes for errors. 23 references. Thanks. 26. 28. Welding technology and automation graduation thesis introduction welding applications as the connection of a flexible and efficient method widely in bridges, shipbuilding, construction, aviation, pressure vessel manufacturing and with the rap

13、id development of Chinas steel structure industry, welding technology has been widely used in steel structures, various production departments in various fields of industry and agriculture, the welding structure throughout the national economy. From the private traffic to rocket missiles and other v

14、ehicles, from agricultural machinery to all kinds of precision machinery and heavy and is everywhere. However, the residual deformation of welded structure that has plagued the field of welding, this phenomenon has become the focus of the concern. The welding deformation is not only cause the weldin

15、g structure of shape variation, reducing the size accuracy and bearing capacity, and the additional moment caused by work load and stress concentration is the main reason of early failure of the welding structure, one of the reasons is caused by the welding structure fatigue strength reduction. Thes

16、e defects are main thermal welding process caused unreasonable. Due to the high concentration of transient heat input, and welding in the welding process will produce large welding residual stress and deformation of welding residual deformation, welding shrinkage, warpage welding residual stress, dy

17、namic stress produced in the welding process and welding residual stress deformation and welding defects,The stability but also affect the structure of the processing precision and size in a certain degree. Therefore, in the design and construction must fully consider the characteristics of welding

18、stress and deformation. Welding is one of the most important ways to connect metal materials into components, either adding or not adding filler metal, including the surfacing weld, the welding process of the most core technology is connecting surface melting, followed by continuous cooling, local h

19、eat input form partial melting, and as far as possible to reduce heat dissipation to the internal components and the loss of heat to the surrounding environment, the welding process is a process of uniform and rapid heating and cooling. The melting welding, welding metal by local heating and melting

20、 in the heat under the effect of mechanical properties of the material will change significantly, but also directly determines the welding process of the weld and heat affected zone, microstructure after welding residual stress and deformation of the size, so the accurate calculation and determinati

21、on of welding thermal process is the premise of welding stress and deformation analysis. To make it simple, commonly used in the actual welding concept as a classification system will be decomposed into welding thermodynamics, mechanics and microstructure of the process, so as to reduce the complexi

22、ty of the phenomena of welding. In the process of welding and welding structure will inevitably produce welding deformation, and the deformation of welding in the construction of the most troublesome is the most difficult to deal with problems. Welding distortion not only affects the structure and a

23、ppearance of size precision and possibly reduce the bearing capacity and mechanical performance, more important is easy to cause the instability of welding structure. In the welding process, the welding deformation not only affects the welding structure of manufacturing process, the welding deformat

24、ion will even seriously affect the manufacturing process, performance, structure of the welding joint fracture resisting ability, fatigue strength, anti stress 1 welding technology and automation graduation thesis corrosion cracking and creep cracking ability. The welding deformation analysis and es

25、timation of welding deformation has important significance. This paper is divided into three chapters, the first chapter introduces the reasons and influencing factors of welding deformation, and analyzes the relationship between species and various types of welding deformation; in the second chapte

26、r, T type welding component as the research object, welding, and longitudinal shrinkage of weld were measured; the third chapter discusses the estimation of welding deformation. And the estimated values are compared with the measured value, so as to provide theoretical basis for production practice.

27、 2 welding technology and automation graduation thesis the first chapter of welding deformation and its influencing factors of 1.1 welding deformation of welding stress and deformation is the result of interaction by a variety of factors caused. Usually, if only the effect of restraint in terms of w

28、elding stress and deformation can be express as follows. The welding heat input caused by local heating of inhomogeneous material, the weld zone and high temperature zone melting; thermal expansion and adjacent to the pool is surrounded by material constraints, resulting in uneven compressive plasti

29、c deformation; in the cooling process, this part has occurred compressive plastic deformation is also restricted by the surrounding conditions, but not free contraction in different degrees by stretching and unloading; at the same time, solidification of molten pool, metal cooling shrinkage has also

30、 produced the corresponding shrinkage tensile stress and deformation. So, in the area of welded joint has shortened incompatible strains. The welding deformation causes are the following: (1) the uneven local heating and cooling is the main reason. When welding test plate is heated to melt the local

31、 state, form the uneven distribution of regional test plate temperature, the test plate appears uneven thermal expansion, thermal expansion by the surrounding metal hindering free expansion under compressive stress, the surrounding metal is subjected to tensile stress. In the high temperature region

32、 near the weld seam side by thermal pressure, away from the weld side by thermal stress. When the heated metal by pressure stress exceeds the yield point, will cause plastic deformation. The plate cooling, the weld has different cooling time, first the first welding solidification, has certain stren

33、gth, prevent weld after welding in the horizontal expansion of freedom, which results in the transverse compression deformation.Weld cooling after welding when the transverse shrinkage is prevented, and the transverse tensile stress, and the first welding part produces transverse compressive stress.

34、 Due to the heating of metal in heating has produced plastic deformation, so the compression, finally a length less than the length of the metal heating is not short. (2) the weld metal and HAZ microstructure change. The weld and HAZ metal in welding when heated to the melting point or solid phase t

35、ransition temperature above the metal cooling process to change. Because the volume of various tissues are different, so the volume change occurs. (3) the rigid steel structure is symmetrical in structure, weld layout, reasonable welding procedure can only generate linear shortening; when the weld l

36、ayout asymmetry, will produce bending deformation; the cross section of the weld joint center of gravity and the center section in the same position, if the welding procedure is reasonable, only when the linear shortening; the cross section of the weld joint section of gravity center of gravity, wil

37、l produce angular deformation. The weld amount is more, the greater the deformation. (4) welding component after forming, should according to the different geometric size and shape components make the welding process correctly, the work on the control of welding deformation is significant, most of t

38、he amount of deformation is due to the welding process caused by incorrect, such as welding current, electrode diameter, welding speed of crude, will the welding deformation. 3 multilayer welding, welding technology and automation of graduation thesis of the first layer of weld shrinkage is the larg

39、est, the more layers of welding deformation is greater. Intermittent weld than the continuous weld shrinkage of small, welding sequence improper or not weld segment components, then assembled and welded, are easy to produce welding deformation in the construction, so it is important to develop reaso

40、nable welding process. 1.2 the classification of welding deformation and the relation between the welding deformation is generally in accordance with the deformation characteristics are divided into the following 7 categories: 1) transverse shrinkage due to the heating heat source of welding arc and

41、 subsequent cooling, the temperature is perpendicular to the welding member length and thickness direction is not homogeneous, which produce transverse shrinkage strain and transverse residual the stress in welding joint. Causes of transverse shrinkage, partly due to the shrinkage of weld metal afte

42、r cooling, the other part is the expansion of the weld metal hot forming blocked transverse residual plastic deformation caused by the. Transverse contraction deformation and the deflection deformation. The lateral deformation of the size of the welding line energy and thickness, with the increase o

43、f welding line energy, transverse shrinkage increases; with the increase of thickness, transverse shrinkage reducing. The distribution of transverse deformation along the weld length is not uniform. This is because the first transverse shrinkage welding of weld after a compression effect, which caus

44、es more lateral compression deformation. Therefore, the weld transverse contraction along the welding direction is increasing gradually increase, to a certain extent tends to be stable. In addition, the transverse shrinkage by manual electric arc welding automatic submerged arc welding when the tran

45、sverse shrinkage ratio of plate thickness is similar to the small deformation by welding, when the transverse shrinkage ratio of transverse shrinkage of large amount of manual electric arc welding. If the asymmetric distribution of the transverse weld in the structure, so it can also cause the later

46、al contraction deformation of structure deflection. 2) the longitudinal contraction in welding, due to uneven temperature distribution along the weld direction, and near the weld metal had longitudinal compressive residual plastic deformation. The plastic deformation area called plastic deformation

47、zone. The construction of longitudinal contraction deformation depends on the size of the plastic deformation zone, the construction area, and the length of weld welding line energy. Because of the plastic deformation zone by the contraction of the surrounding metal block, so relatively less signifi

48、cant lateral contraction of longitudinal contraction. The theory that the longitudinal systolic volume is about 1 / 1000 of the length of the weld. Longitudinal contraction deformation and flexural deformation caused by it. Longitudinal contraction deformation depends mainly on component length, cro

49、ss-sectional area and compressive plastic deformation size. While the compressive plastic deformation associated with the thermal physical parameters of materials and welding sequence, welding method, welding parameters. In the process of welding line energy Q (Qq/v, for energy,V is the main welding

50、 speed). In general, the relationship between longitudinal contraction deformation and welding line energy is proportional to the. For the same cross-sectional area of the weld, the multilayer welding each welding line energy is much smaller than single-layer welding, so the longitudinal contraction

51、 caused by multilayer welding than single-layer welding small. The more layers, each layer with the line energy is smaller, the deformation is smaller. Similarly, the longitudinal contraction deformation of discontinuous welding than continuous welding is much smaller. When the weld in the 4 welding

52、 technology and automation graduation on file in the location of asymmetry, the weld induced stress is not uniform, so it not only makes the component shortened, also make the component bending deflection produced. The longitudinal and lateral retraction of figure 1-1. Figure 1-1 transverse shrinkag

53、e and longitudinal shrinkage 3) deflection component after welding bending in shape. Mainly because of the shrinkage of the same side or on both sides of the weld, shrinkage deformation and the other side remains unchanged and cause, see figure 1-2. Figure 1-2 deflection angle deformation) 4. The an

54、gular displacement of crack plane around the weld after welding structure. Is mainly due to the plate thickness direction of weld shrinkage deformation caused by different. In welding, butt and lap welding of T-joint, due to transverse contraction deformation in the thickness direction of the uneven

55、 distribution, tend to produce angular deformation. Angular deformation depends on the size of the component size and distribution of compressive plastic deformation, but also depends on the stiffness of the plate. For the same thickness, with the increase of welding line energy, both sides of the plastic deformation quantity difference will increase, the angular distortion will al