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Welding technique for base plate of LNG low-temperature tank

A welding process and low-temperature tank technology, applied in welding equipment, manufacturing tools, metal processing, etc., can solve problems such as easy burn-through, poor formation of lap fillet welds, welding thermal cracks, etc., achieve good mechanical properties, reduce welding Effects of heat input and pressure-bearing capacity improvement

Inactive Publication Date: 2015-05-20
SINOPEC TENTH CONSTR
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a welding process for the bottom plate of the LNG low-temperature tank. Poor seam formation, welding hot cracks, and easy burn-through during welding, and in actual operation, two 9Ni steel plates with a thickness of 6~9mm can be welded in one pass in one pass, which significantly improves the welding efficiency

Method used

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  • Welding technique for base plate of LNG low-temperature tank

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Effect test

Embodiment 1

[0029] Embodiments 1 to 4 are specific implementations of the welding process of the bottom plate of the LNG low-temperature tank of the present invention, wherein embodiment 1 is the best embodiment.

[0030] refer to figure 1 The contact tip 3 of the welding trolley is fixed with a welding wire 5, which is used as the base material to weld the upper 9Ni steel plate 1 and the lower 9Ni steel plate 2 of the bottom plate of the LNG low-temperature storage tank to overlap each other to form a lap joint, and the lap joint does not open a groove. The bottom plate of the LNG low-temperature storage tank is composed of multiple sets of overlapping upper 9Ni steel plates 1 and lower 9Ni steel plates 2, the thickness c of the upper 9Ni steel plates is 6~9mm, and the thickness d of the lower 9Ni steel plates is 6~9mm. The welding root is the junction of the overlapping area of ​​the upper 9Ni steel plate 1 and the lower 9Ni steel plate 2 on the back of the fillet weld 6 , that is, the ...

Embodiment 2

[0038] This embodiment includes the following steps:

[0039] 1) Form a lap joint: lap two 9Ni steel plates with a thickness of 7 mm horizontally, and form a lap joint at the overlap;

[0040] 2) Clean the end face: Use an angle grinder to clean and polish the end face of the lap joint until the end face appears metallic luster; clean the surface of the 9Ni steel plate within 60mm from the lap joint, and remove moisture, oil and dust within this range ;The grinding machine uses black silicon carbide as the abrasive and rubber as the adhesive grinding wheel;

[0041] 3) Preparatory welding: place the welding trolley in parallel with the reserved fillet weld area at the end face of the lap joint, aim the welding torch at the fillet weld area before welding, and keep the distance between the end of the welding wire and the welding root at 0 ~5mm, the welding trolley walks along the weld seam in advance, planning the path of the welding trolley during the welding process;

[004...

Embodiment 3

[0044] This embodiment includes the following steps:

[0045] 1) Form a lap joint: lap two 9Ni steel plates with a thickness of 8 mm horizontally, and form a lap joint at the overlap;

[0046] 2) Clean the end face: Use an angle grinder to clean and polish the end face of the lap joint until the end face appears metallic luster; clean the surface of the 9Ni steel plate within 60mm from the lap joint, and remove moisture, oil and dust within this range ;

[0047] The grinding machine uses black silicon carbide as the abrasive and rubber as the adhesive grinding wheel;

[0048] 3) Preparatory welding: place the welding trolley in parallel with the reserved fillet weld area at the end face of the lap joint, aim the welding torch at the fillet weld area before welding, and keep the distance between the end of the welding wire and the welding root at 0 ~5mm, the welding trolley walks along the weld seam in advance, planning the path of the welding trolley during the welding proce...

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Abstract

The invention discloses a welding technique for a base plate of an LNG low-temperature tank and belongs to the technical field of welding of LNG low-temperature tanks. According to the welding technique, two 9Ni steel plates with the thicknesses ranging from 6 mm to 9 mm are made to be in lap joint in the horizontal direction and overlap to form an overlap joint, the end face is cleaned, a preparation for welding is made, and then submerged-arc welding is conducted by means of alternating current, wherein the arc voltage ranges from 25 V to 29 V, the welding current ranges from 260 A to 290 A, the wire extension length ranges from 25 mm to 35 mm, the welding speed ranges from 22 in / min to 25 in / min, the welding wire angle ranges from 55 degrees to 65 degrees, and a full fillet weld with a welding foot with the length ranging from 6 mm to 9 mm is formed. By the adoption of the welding technique, submerged-arc welding of the base plate of the LNG low-temperature tank can be achieved, the problems that during submerged-arc welding, a lap fillet weld is poorly formed, hot cracks are formed during welding, and burning through occurs easily during welding are solved, the two 9Ni steel plates with the thicknesses ranging 6 mm to 9 mm can be welded in a single-pass mode at a time during actual operation, and welding efficiency is remarkably improved.

Description

technical field [0001] The invention discloses a welding process for the bottom plate of an LNG low-temperature tank, belonging to the technical field of LNG low-temperature tank welding. Background technique [0002] LNG cryogenic tank, full name LNG cylindrical atmospheric pressure cryogenic storage tank, can be divided into single-containment, double-containment and full-containment types, the design pressure is usually -6mbarg ~ 140mbarg, if the concrete tank roof is used, the weight is heavy, and the positive design The pressure can be even higher. Since the temperature difference between the inside and outside of the LNG cryogenic tank can reach up to 200°C, the temperature inside the tank can reach -160°C. In the field of 9Ni steel welding technology, the bottom plate of the LNG low-temperature tank welded with 9Ni steel girth seam needs to achieve sufficient pressure bearing capacity. If the weld of the bottom plate of the LNG low-temperature tank has unstable weldi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K9/18B23K9/235
CPCB23K9/186B23K9/235B23K2101/125
Inventor 马志才赵喜平杨连文杨永强唐元生
Owner SINOPEC TENTH CONSTR
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