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平面钢闸门的设计与焊接要求
更新时间:12-17 11:28
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  平面钢闸门结构生产制造工作,质量的控制贯穿整个工作的全过程,作者认为门叶焊接是闸门焊接的关键,门叶的焊接变形控制必须得到有效控制。如果焊前不充分交底和焊接把关,焊后会产生较大的焊接变形,甚至使变形无法修复而造成构件报废,所以,我们专门制订了焊接工艺设计。对闸门的一、二类焊缝编制了“主控项目”焊接工艺卡,要求参加闸门焊接的合格焊工严格遵循工艺纪律及各项技术要求,有效地控制了闸门的焊接变形,提高了产品的生产质量,收到了良好的经济效益。
   5d0304fba3de0  2. 闸门的技术要求
  2.1 钢闸门的焊接,除按标书技术要求及水利水电工程钢闸门制造安装及验收规范来确保焊接质量符合规定外,焊接变形则是控制整体制造的首要问题
  2.2 门叶整体拼装组对时,各部位间隙要严格控制。如:主梁与面板,主梁腹板、翼板与隔板,主梁与边梁之间等结合部位要顶紧装配,各组合面的局部间隙均不大于1mm,严禁强行组装。
  2.3 整体闸门制作若分节,按制造结构的设计工艺要求,整体拼装后为保证整体闸门门叶的焊接要求,在各节连接部位之间,每隔500mm左右要有临时加强肋板,以加强闸门门体的刚度。
  2.4 门叶组装完毕后,由检查人员对整体尺寸、组装质量、坡口大小、组合间隙等进行严格认真的检查。如不合格必须按要求进行整改,直至合格为止。
  2.5 闸门检查合格后,由合格焊工对闸门进行整体加固。每300mm左右加固长度必须要有一段长100mm左右的加固焊(焊脚高度不宜超过设计焊脚或坡口的1/2~1/3)。加固焊要求同正式焊要求一致,不得有裂纹、夹渣、气孔等焊接缺陷。
  2.6 焊材使用时,应按焊接工艺设计要求进行烘焙后使用。焊工应随身携带焊条保温筒,做到随用随取。焊条在保温筒内的存放时间不得超过4h,否则焊材应重新烘焙,重复烘焙次数不得超过2次。焊剂烘干需按单位制度要求或使用说明书进行。焊接参数见表1。
  2.7 当局部组装间隙超过5mm时,且长度不大于焊缝全长的15%,允许堆焊处理。堆焊时严禁填充异物且堆焊后进行修复直至达到设计要求。
  2.8 严格按照焊接规范执行,具体焊接参数见表1。多层多道焊时,应注意焊道周围的清理工作,层间接头应错开50mm以上,严禁在非焊接部位的母材上随意引弧。
  2.9 焊接热输入、焊接速度和焊接层数。焊接热输入太大时,会导致热影响区性能下降、尤其是韧性降低,为了尽可能减小这种影响的程度,获得良好性能的焊缝和成型,就必须对焊接热输入加以控制。焊接速度应在焊接热输入允许范围内。焊接层数根据板厚、焊脚尺寸、焊条直径来确定,每层厚度应小于6mm。
  2.10 在埋弧焊时,对于一、二类焊缝必须参照“焊接工艺卡”进行施焊。
  2.11 埋弧焊拼板、T型梁船位焊接,焊缝的引弧、熄弧处应加引弧或熄弧板,一般应在端部50mm 
  处施加。
  2.12 仪表、机械、焊机等应工作正常。焊丝不得有小角度弯曲,焊丝和工件表面不得有油、水、锈等污物。
  2.13 一、二类焊缝中如有缺陷需修补时,应由持有效期内的合格焊工按有关工艺进行。对于一、二类焊缝,同一位置的返修次数不宜超过2次。超过2次的返修处理,需经总工程师批准,且做出返修工 
  艺和返修记录。
   
  3. 焊接变形产生的原因
  焊接变形产生的最根本原因是焊件受热或冷却不均匀,焊缝金属的收缩、金相组织的变化及焊件的刚性是产生或影响焊接应力和变形的重要原因。由以上分析可见,焊接应力变形产生的根源是焊接受热不均,膨胀不自由,因而产生不均匀压缩塑性变形所造成的。这种压缩塑性变形在随后的冷却收缩过程中,如果工件板面较窄,厚度较薄,收缩阻碍较小,就表现为焊缝宽度、长度方向的收缩变形。否则,如果板面较宽,厚度较大,焊缝纵向的冷却收缩受到两侧冷金属的阻碍,就会对冷收缩金属产生拉伸作用,并在工件中残留较大的残余应力。如果焊接结构的刚度较大,焊缝的横向收缩受到较大的限制,则在这些结构中还将残留巨大拘束应力。采 
  用合理的工艺手段,使焊接收缩能自由的释放,或互相抵消,或在焊接过程中消除,这样可使焊接应力变形都较小。
   
  4. 焊接变形的控制要点
  4.1 在组装和连接一个结构或组合构件的部件时,以及在焊接加强部件至构件时,焊接顺序应使焊接变形和收缩最小。
  4.2 在焊接过程中,所有焊接的顺序应尽可能使焊接进展时所施加热量均衡(注:焊接线能量确定时)。
  4.3 在构件施焊时,焊接走向应从工件相对固定的点开始,向有较大自由位移的点移动。
  4.4 在组装好的构件中,应先焊收缩量较大接头(即厚板坡口等),后焊收缩量较小的接头,在焊接时,要尽可能没有约束力或约束力较小为好。
  4.5 对于闸门的工字型焊接主梁、T型梁或组合件的每个部件(即小组、中组的结构件),应在小组、中组焊接前,事先应全部拼接、校正好后再组对。
   
  5. 闸门的焊接工艺
  闸门组装完工后进行整体焊接。为了保证门叶尺寸、焊接质量和控制焊接变形,要求由4名焊工完成作业任务,对于小型闸门,由2名焊工完成作业。按作业顺序和方向进行施工,由4名焊工采用相同的焊接规范,同时由中心向两侧分段、间隔、对称进行焊接。构件空间位置焊接顺序:先焊立焊,后焊贴脚焊,最后其余焊缝。
   
  6. 焊接检验
  6.1 外观检验执行DL/T5018-94《水利水电工程钢闸门制造及验收规范》标准规定。
  6.2 无损检测执行GB3323-87《钢熔化焊对接接头射线照相和质量分级》、GB11345-89《钢焊缝手工超声波探伤方法和探伤结果分析》标准规定。无损检验均应在焊后24h进行In the production and manufacture of planar steel gate structure, the quality control runs through the whole process of the work. The author considers that the welding of gate blade is the key to the welding of gate, and the welding deformation control of gate blade must be effectively controlled. If there is insufficient cross-over before welding and welding checkpoint, there will be large welding deformation after welding, even the deformation can not be repaired and the components will be scrapped. Therefore, we specially formulated the welding process design. For the first and second type welds of the gate, the welding process card of "main control project" has been compiled, requiring qualified welders to take part in the welding of the gate to strictly follow the process discipline and various technical requirements, effectively controlling the welding deformation of the gate, improving the production quality of the product and receiving good economic benefits. 2. Technical requirement of gate. Welding of 2.1 steel gate, besides ensuring the welding quality in accordance with the technical requirement of tender and the specifications of manufacture, installation and acceptance of steel gate in water conservancy and Hydropower projects, is the primary problem to control the overall manufacturing. When 2.2 door blades are assembled together, the clearance of each part should be strictly controlled. For example, the main girder and the panel, the web of the main girder, the flange and the partition of the main girder, and the joint between the main girder and the side girder should be tightly assembled, and the local clearance of each combination surface should not be greater than 1 mm. Forced assembly is strictly prohibited. 2.3 If the integral gate is divided into sections, according to the design process requirements of the manufacturing structure, in order to ensure the welding requirements of the integral gate blades after the integral assembly, temporary ribs should be strengthened every 500 mm or so between the connecting parts of each section to strengthen the stiffness of the gate body. After 2.4 door blades are assembled, the inspectors will examine the overall size, assembly quality, groove size and assembly clearance strictly and seriously. If they are not qualified, they must be rectified as required until they are qualified. After the 2.5 gate is qualified, the qualified welder shall reinforce the gate as a whole. Every 300 mm or so reinforcement length must have a reinforcing welding with a length of about 100 mm (the height of the welded foot should not exceed 1/2 to 1/3 of the designed welded foot or groove). The requirement of reinforcement welding is consistent with the requirement of formal welding, and no welding defects such as cracks, slag inclusion and pore are allowed.  When using 2.6 welding material, it should be baked and used according to the requirements of welding process design. Welders should carry the welding rod insulating cylinder with them, so that they can be used as they like. The storage time of the welding rod in the incubator shall not exceed 4 hours, otherwise the welding material shall be re-baked and the number of repeated baking shall not exceed 2 times. Flux drying should be carried out according to unit system requirements or instructions. Welding parameters are shown in Table 1. 2.7 Surfacing treatment is allowed when the assembly clearance exceeds 5 mm and the length is not more than 15% of the total length of the weld. It is strictly forbidden to fill foreign body during surfacing and repair it after surfacing until it meets the design requirements. 2.8 is strictly in accordance with the welding specifications. The specific welding parameters are shown in Table 1. In multi-layer and multi-pass welding, attention should be paid to the cleaning work around the weld bead. The indirect joint of the layer should be staggered more than 50 mm. Arc initiation on the base metal of the non-welded part is strictly prohibited. 2.9 Welding heat input, welding speed and number of welding layers. When the welding heat input is too large, the performance of HAZ will decrease, especially the toughness. In order to minimize the influence and obtain good welding seam and forming performance, it is necessary to control the welding heat input. Welding speed should be within the allowable range of welding heat input. The number of welding layers is determined by plate thickness, foot size and electrode diameter. The thickness of each layer should be less than 6 mm. 2.10 In submerged arc welding, the first and second class seams must be welded with reference to the "welding process card". 2.11 submerged arc welding tailor plate and T-beam seam welding. Arc ignition or arc extinguishing plate should be applied at the starting and extinguishing points of weld seam, generally at the end of 50mm. 2.12 Instruments, machinery and welding machines should work normally. Welding wires shall not be bent at small angles, and no oil, water, rust and other contaminants shall be found on the surface of welding wires and workpieces. If any defects in Class I and II welds need to be repaired, the qualified welders within the validity period shall follow the relevant process. For type 1 and type 2 welds, the number of repairs at the same position should not exceed 2 times. Over two repairs should be approved by the Chief Engineer, and the repairs process and record should be made. 3. The most fundamental cause of welding deformation is the uneven heating or cooling of the weld. The shrinkage of the weld metal, the change of the metallographic structure and the rigidity of the weld are the important reasons for producing or influencing the welding stress and deformation. From the above analysis, it can be seen that the root cause of welding stress and deformation is the uneven heating and expansion of welding, resulting in uneven compressive plastic deformation. In the subsequent cooling shrinkage process, if the workpiece plate surface is narrower, the thickness is thinner and the shrinkage hindrance is smaller, the shrinkage deformation in the width and length direction of the weld seam is shown. Otherwise, if the plate surface is wider and the thickness is larger, the longitudinal cooling shrinkage of the weld will be hindered by the cold metal on both sides, which will have a tensile effect on the cold shrinkage metal and residual stress in the workpiece. If the stiffness of the welded structure is large and the transverse shrinkage of the weld seam is limited, the huge restraint stress will remain in these structures. Reasonable technological means are adopted to release the welding shrinkage energy freely, or offset each other, or eliminate it in the welding process, so that the welding stress and deformation are smaller. 4. Control Points of Welding Deformation。


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