阅读说明：本技术 一种全压式液化气运输船储罐的焊接工艺 (Welding process for storage tank of full-pressure liquefied gas transport ship ) 是由 潘雄 易昶 潘海伟 潘海杰 袁浩 王叶青 李旭光 肖洋 何元庆 陈刚 王海平 于 2021-08-25 设计创作，主要内容包括：本发明提供了一种全压式液化气运输船储罐的焊接工艺,包括如下步骤：焊接设备以及附件的检查,焊接电源摆放,脚手架搭设,防风措施搭设,储罐板材准备,焊材准备,储罐板材预热,焊材烘烤,点固焊,焊接,消氢热处理,焊缝检测以及热处理。对储罐板材进行预热,可减少焊接接头的冷却速度,避免产生淬硬组织,减小焊接应力与变形,防止产生焊接裂缝,提升焊缝质量。对储罐板材进行点固焊可有效防止储罐焊缝在施焊过程中发生较大的错边和变形及在预热时由于温度变化的影响产生裂纹,有助于提升焊缝的质量。对储罐进行消氢热处理,使得焊缝中的扩散氢加速逸出,大大降低焊缝中的氢含量,防止产生冷裂纹,提升焊缝质量。(The invention provides a welding process of a storage tank of a full-pressure liquefied gas transport ship, which comprises the following steps: the method comprises the steps of checking welding equipment and accessories, placing a welding power supply, erecting a scaffold, erecting windproof measures, preparing a storage tank plate, preparing a welding material, preheating the storage tank plate, baking the welding material, tack welding, performing dehydrogenation heat treatment, detecting a welding line and performing heat treatment. The storage tank plate is preheated, so that the cooling speed of a welding joint can be reduced, a hardening structure is avoided, the welding stress and deformation are reduced, a welding crack is prevented, and the welding seam quality is improved. The spot welding of the storage tank plate can effectively prevent the storage tank welding seam from generating large misalignment and deformation in the welding process and generating cracks due to the influence of temperature change in the preheating process, and is beneficial to improving the quality of the welding seam. The storage tank is subjected to dehydrogenation heat treatment, so that diffused hydrogen in the welding seam escapes in an accelerated manner, the hydrogen content in the welding seam is greatly reduced, cold cracks are prevented, and the welding seam quality is improved.)

1. A welding process of a storage tank of a full-pressure liquefied gas transport ship is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: checking welding equipment and accessories, and checking whether the welding equipment is intact, whether a welding cable is damaged or not and whether ground wire contact is good or not;

step two: placing a welding power supply, namely placing the welding power supply in a ventilated, dry and clean environment and approaching the welding power supply to a storage tank as close as possible;

step three: erecting scaffolds, wherein the interlayer spacing of the scaffolds is 1.3-1.6 m;

step four: erecting windproof measures, namely erecting windproof tarpaulin on a scaffold;

step five: preparing a storage tank plate, namely selecting a P690QL1 steel plate as the storage tank plate;

step six: preparing a welding material, namely selecting an ultralow-hydrogen high-toughness OK75.75 welding rod as the welding material;

step seven: preheating the storage tank plate, namely preheating a P690QL1 steel plate, wherein the preheating temperature is not lower than 100 ℃;

step eight: baking the welding material, namely baking the ultralow-hydrogen high-toughness OK75.75 welding rod for two hours at 350-400 ℃, and then placing the welding rod in a low-temperature constant temperature box for heat preservation at 100-150 ℃;

step nine: tack welding, wherein tack welding is carried out in a small groove of a welding seam, the length of the tack welding is 150mm, the thickness of the tack welding is more than or equal to 13mm, and the spacing between tack welding beads is 500 mm;

step ten: welding, wherein the principle of the welding sequence is that a longitudinal seam is welded firstly, then a circular seam is welded, a large groove is welded firstly, and then a small groove is welded;

step eleven: performing dehydrogenation heat treatment, namely heating the storage tank at 300-350 ℃ for 30 minutes to enable hydrogen to escape at high temperature, and then heating the storage tank at 200-300 ℃ for 30 minutes to improve the strength of the storage tank and eliminate the possibility of generating cracks;

step twelve: detecting the welding seam, wherein a professional inspector inspects the welding seam;

step thirteen: and (4) performing heat treatment, namely placing the storage tank at 200-350 ℃ for 45 minutes to eliminate residual stress.

2. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the fourth step, in order to ensure the fire-proof safety, the tarpaulin uniformly selects the flame-retardant tarpaulin.

3. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: and seventhly, the heating part is arranged on the other side of the welding part, and the width of the heating part is not less than 300 mm.

4. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: a fourteenth step is further performed before the eighth step and the ninth step: cleaning before welding, and cleaning up oil stain, water and other harmful impurities on the surface and two sides of the groove within the range of at least 20 mm.

5. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the ninth step, the tack welding sequence is that the two ends of the welding seam are tack welded firstly, then the middle is tack welded, and then the two ends are symmetrically encrypted one by one.

6. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the ninth step, arc striking and arc extinguishing of spot welding are carried out in the groove, arc striking and arc extinguishing on the shell plate of the storage tank are strictly forbidden, and arc pits are filled during arc extinguishing.

7. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the step ten, the manual welding of the welding rod adopts direct current reverse connection, the current is 120-180A, the voltage is 23-28V, the welding speed is 8-20 cm/min, and the linear energy is 10-40 kJ/cm.

8. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the step ten, after welding of each layer is finished, the slag is cleaned, the defective positions are cleaned, and the next layer of welding can be carried out after repair welding and grinding.

9. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the step ten, after the welding seam is completely welded on the large-groove side, the carbon arc gouging is used for back chipping on the small-groove side, magnetic powder or dye inspection is carried out after grinding, and after defect-free welding is confirmed, small-groove welding can be carried out.

10. The welding process of the storage tank of the full-pressure liquefied gas transport ship according to claim 1, which is characterized in that: in the step ten, the undercut depth of the butt weld is not more than 0.5 mm; the continuous length of the undercut is not more than 100 mm; the total length of the undercut at both sides of the weld must not exceed 10% of the length of the weld.

Technical Field

The invention relates to a welding process of a liquefied gas transport ship, in particular to a welding process of a storage tank of a full-pressure liquefied gas transport ship.

Background

The liquefied gas carrier is a liquid cargo ship for specially carrying liquefied gas, and can be divided into a liquefied natural gas ship and a liquefied petroleum gas ship. A liquefied gas storage tank is an important component of a liquefied gas carrier for storing liquefied petroleum gas in a low-temperature liquid state. Because the special use environment of the liquefied gas storage tank requires the liquefied gas storage tank to have higher strength and welding seam quality, how to meet the requirements and weld the liquefied gas storage tank by the simplest process becomes an extremely important problem to be solved urgently.

Disclosure of Invention

In view of the above, the present invention provides a welding process for a storage tank of a full-pressure liquefied gas carrier, which has the advantages of high strength of the storage tank and high quality of welding seams after welding.

In order to solve the technical problems, the technical scheme of the invention is as follows: a welding process for a storage tank of a full-pressure liquefied gas transport ship comprises the following steps:

the method comprises the following steps: checking welding equipment and accessories, and checking whether the welding equipment is intact, whether a welding cable is damaged or not and whether ground wire contact is good or not;

step two: placing a welding power supply, namely placing the welding power supply in a ventilated, dry and clean environment and approaching the welding power supply to a storage tank as close as possible;

step three: erecting scaffolds, wherein the interlayer spacing of the scaffolds is 1.3-1.6 m;

step four: erecting windproof measures, namely erecting windproof tarpaulin on a scaffold;

step five: preparing a storage tank plate, namely selecting a P690QL1 steel plate as the storage tank plate;

step six: preparing a welding material, namely selecting an ultralow-hydrogen high-toughness OK75.75 welding rod as the welding material;

step seven: preheating the storage tank plate, namely preheating a P690QL1 steel plate, wherein the preheating temperature is not lower than 100 ℃;

step eight: baking the welding material, namely baking the ultralow-hydrogen high-toughness OK75.75 welding rod for two hours at 350-400 ℃, and then placing the welding rod in a low-temperature constant temperature box for heat preservation at 100-150 ℃;

step nine: tack welding, wherein tack welding is carried out in a small groove of a welding seam, the length of the tack welding is 150mm, the thickness of the tack welding is more than or equal to 13mm, and the spacing between tack welding beads is 500 mm;

step ten: welding, wherein the principle of the welding sequence is that a longitudinal seam is welded firstly, then a circular seam is welded, a large groove is welded firstly, and then a small groove is welded;

step eleven: performing dehydrogenation heat treatment, namely heating the storage tank at 300-350 ℃ for 30 minutes to enable hydrogen to escape at high temperature, and then heating the storage tank at 200-300 ℃ for 30 minutes to improve the strength of the storage tank and eliminate the possibility of generating cracks;

step twelve: detecting the welding seam, wherein a professional inspector inspects the welding seam;

step thirteen: and (4) performing heat treatment, namely placing the storage tank at 200-350 ℃ for 45 minutes to eliminate residual stress.

Through the technical scheme, the P690QL1 steel plate and the OK75.75 welding rod have the certificate of the classification society and the quality certificate approved by the factory, and the storage tank produced by the two materials has the advantages of high structural strength and high welding seam quality. The inspection of the welding equipment and accessories can avoid the operation with faults and ensure the welding quality. The welding power supply is placed in a ventilated, dry and clean environment, so that the welding power supply is not prone to failure, and welding quality is guaranteed. The welding power supply is close to the storage tank as much as possible, so that the accuracy of welding parameter control can be improved, the current loss and the voltage drop are reduced, and the welding quality is ensured. The distance between the scaffold layers is 1.3m-1.6m, so that a welder can conveniently perform welding operation. The influence of wind on welding can be reduced by erecting the windproof tarpaulin, and the welding quality is improved. The storage tank plate is preheated, so that the cooling speed of a welding joint can be reduced, a hardening structure is avoided, the welding stress and deformation are reduced, a welding crack is prevented, and the welding seam quality is improved. After the welding material is baked, bubbles can be effectively prevented from being generated at the welding seam, and the quality of the welding seam is improved. The spot welding of the storage tank plate can effectively prevent the storage tank welding seam from generating large misalignment and deformation in the welding process and generating cracks due to the influence of temperature change in the preheating process, and is beneficial to improving the quality of the welding seam. The storage tank is subjected to dehydrogenation heat treatment, so that diffused hydrogen in the welding seam escapes in an accelerated manner, the hydrogen content in the welding seam is greatly reduced, cold cracks are prevented, and the welding seam quality is improved. And carrying out heat treatment on the storage tank to eliminate residual stress and improve the structural strength of the storage tank.

Preferably, in the fourth step, in order to ensure fire safety, the tarpaulin uniformly adopts the flame-retardant tarpaulin.

Through the technical scheme, the flame-retardant tarpaulin is not easy to be ignited by scattered sparks in the welding process, and the fireproof safety is higher.

Preferably, in the seventh step, the heating part is on the other side of the welding part, and the width is not less than 300 mm.

Through above-mentioned technical scheme, the width of heating portion is not less than 300mm, so can promote the temperature of whole storage tank panel, and the heating effect is better.

Preferably, step eight is preceded by step nine by step fourteen: cleaning before welding, and cleaning up oil stain, water and other harmful impurities on the surface and two sides of the groove within the range of at least 20 mm.

Through above-mentioned technical scheme, with the greasy dirt of the at least 20mm within range of groove surface and both sides, moisture and other harmful impurity clean up, impurity is difficult for entering into the welding seam like this, ensures the quality of welding seam.

Preferably, in the ninth step, the tack welding sequence is to tack both ends of the weld, then tack the middle, and then symmetrically encrypt the two ends one by one.

Through above-mentioned technical scheme, the order of above-mentioned electric welding can carry out more effectual fixed to storage tank panel for storage tank panel is difficult for appearing great wrong limit and deformation in welding process, and is difficult for producing the crackle because temperature variation's influence in preheating process.

Preferably, in the ninth step, arc striking and arc extinguishing of tack welding are carried out in the groove, arc striking and arc extinguishing on the shell plate of the storage tank are strictly prohibited, and the arc pit is filled during arc extinguishing.

Through above-mentioned technical scheme, can carry out more effectual fixed to storage tank panel for storage tank panel is difficult for appearing great wrong limit and deformation in welding process, and is difficult for producing the crackle because of temperature variation's influence at preheating process.

Preferably, in the step ten, the manual welding of the welding rod adopts direct current reverse connection, the current is 120-180A, the voltage is 23-28V, the welding speed is 8-20 cm/min, and the linear energy is 10-40 kJ/cm.

By the technical scheme, welding heat input energy is an important factor influencing the quality of a welding joint, the heat affected zone is widened due to excessive heat input energy, the notch toughness of weld metal and a fusion line is reduced, the heat affected zone structure with high hardness and low toughness can be caused due to excessive heat input energy, and hydrogen induced cracking can be generated. By adopting the welding line energy and the welding speed, the influence can be reduced to the minimum, and the welding seam quality is improved.

Preferably, in the step ten, after welding of each layer is finished, the slag should be cleaned, the defective parts should be cleaned, and after repair welding and grinding, the next layer of welding can be performed.

Through above-mentioned technical scheme, can effectively avoid the slag to enter into next layer welding to the slag clearance, clear away defect department totally, help promoting the welding seam quality.

Preferably, in the step ten, after the welding seam is completely welded on the large-groove side, the small-groove side is subjected to back gouging by a carbon arc gouging machine, and after the grinding and magnetic powder or dye inspection are carried out, and no defect is confirmed, the small-groove welding can be carried out.

Through above-mentioned technical scheme, the welding seam quality after above-mentioned processing is higher, and the structural strength of storage tank is higher.

Preferably, in the step ten, the undercut depth of the butt weld is not more than 0.5 mm; the continuous length of the undercut is not more than 100 mm; the total length of the undercut at both sides of the weld must not exceed 10% of the length of the weld.

Through the technical scheme, the undercut of the welding seam is controlled, the quality of the welding seam can be improved to a great extent, and the structural strength of the storage tank is improved.

Detailed Description

The following detailed description of specific embodiments of the present invention is provided to facilitate understanding and appreciation of the inventive concepts.

A welding process for a storage tank of a full-pressure liquefied gas transport ship comprises the following steps:

the method comprises the following steps: before welding, whether welding equipment is intact, whether a welding cable is damaged or not and whether ground wire contact is good or not are carefully checked, problems are found, and welding is carried out after timely repairing is carried out, so that operation with faults is avoided;

step two: the welding power supply is placed in a ventilated, dry and clean environment, the power supply of the welding power supply is distributed independently and cannot be used in parallel with other loads, voltage fluctuation and phase deviation are prevented, welding quality is prevented from being influenced, and in order to achieve accuracy of welding parameter control and reduce current loss and voltage drop, the welding power supply is close to the storage tank as much as possible;

step three: erecting a scaffold, wherein the requirement of rotating a rotating tire and the convenience of operation of a welder are considered in the erecting of the scaffold, and the interlayer spacing of the scaffold is 1.3-1.6 m;

step four: the windproof measures are set up, in order to reduce the influence of natural weather factors on the welding process, a windproof tarpaulin is set up around the welding part around the tank body by utilizing a scaffold, all tarpaulins are uniformly flame-retardant tarpaulins for fire prevention safety, and the windproof tarpaulin is set up tightly;

step five: preparing a storage tank plate, wherein a P690QL1 steel plate produced by ESBA in Sweden is selected as the storage tank plate;

step six: preparing a welding material, namely selecting an ultralow-hydrogen high-toughness OK75.75 welding rod as the welding material;

step seven: preheating a storage tank plate, namely preheating a P690QL1 steel plate, wherein the preheating temperature is not lower than 100 ℃, a heating part is arranged on the other side of the welding part, and the width is not less than 300 mm;

step eight: baking the welding material, namely baking the ultralow-hydrogen high-toughness OK75.75 welding rod for two hours at 350-400 ℃, and then placing the welding rod in a low-temperature constant temperature box for heat preservation at 100-150 ℃;

fourteen steps: cleaning before welding, namely cleaning oil stains, water and other harmful impurities on the surface and two sides of the groove within the range of at least 20 mm;

step nine: tack welding, namely performing tack welding in a small groove of a welding seam, wherein the length of the tack welding is 150mm, the thickness of the tack welding is larger than or equal to 13mm, the distance between tack welding beads is 500mm, the tack welding sequence is that two ends of the welding seam are tack welded firstly, then the middle of the tack welding is tack welded, and the two ends are symmetrically encrypted one by one, the tack welding is performed by two groups of people symmetrically and simultaneously by the central axis of the storage tank and rotates in the same direction, the arc striking and the arc extinguishing of the tack welding are carried out in the groove, the arc striking and the arc extinguishing are forbidden to be carried out on a shell plate of the storage tank, and an arc pit is filled when the arc is closed;

step ten: welding, wherein the welding sequence is characterized in that a longitudinal seam is welded and a circular seam is welded, a large groove is welded and a small groove is welded, the manual welding of welding rods adopts direct current reverse connection, the current is 120-180A, the voltage is 23-28V, the welding speed is 8-20 cm/min, the linear energy is 10-40 kJ/cm, after each layer of welding is finished, the molten slag is cleaned, the defective part is cleaned, the repair welding is carried out, the next layer of welding can be carried out, after the large groove side of the welding seam is completely welded, the small groove side is gouged by carbon arc gas, the magnetic powder or the colored flaw detection is carried out after the defect is ground, the small groove welding can be carried out after the confirmation, and the undercut depth of the butt welding seam is not more than 0.5 mm; the continuous length of the undercut is not more than 100 mm; the total length of undercut at two sides of the welding seam is not more than 10% of the length of the welding seam;

step eleven: performing dehydrogenation heat treatment, namely heating the storage tank at 300-350 ℃ for 30 minutes to enable hydrogen to escape at high temperature, and then heating the storage tank at 200-300 ℃ for 30 minutes to improve the strength of the storage tank and eliminate the possibility of generating cracks;

step twelve: and (3) detecting the welding line, wherein a professional inspector inspects the welding line, and the welding line and the surface of a heat affected zone are required not to have defects such as cracks, air holes, slag inclusions, pits, undercuts, arc holes and the like, if the surface of the welding line has the defects such as scratches, electric arc scratches, craters and the like with the depth of more than 0.5mm, the welding line is required to be smoothly polished, and when the depth of the defects and the polishing depth exceed 1mm, the welding line is required to be additionally welded and is required to be smoothly polished.

Step thirteen: and (4) performing heat treatment, namely placing the storage tank at 200-350 ℃ for 45 minutes to eliminate residual stress.

The above are only typical examples of the present invention, and besides, the present invention may have other embodiments, and all the technical solutions formed by equivalent substitutions or equivalent changes are within the scope of the present invention as claimed.