Welding repair method for in-service coke tower

Abstract

The invention discloses a welding repair method for an in-service coke tower. The welding repair method comprises the following steps: step 1, damage evaluation; step 2, material selection; step 3, surface treatment; step 4, preheating treatment; fifthly, welding repair is conducted; sixthly, postweld heat treatment is conducted; step 7, quality inspection; the targeted repair method is designed, proper welding materials and repair technologies can be selected according to the specific depth and position of the crack, the targeted operation mode ensures the accuracy and effectiveness of repair work, the overall effect after repair is improved, and the repair efficiency is improved through the measures of preheating, postweld heat treatment and the like. The hydrogen embrittlement phenomenon possibly occurring in the welding process is effectively eliminated, the structural integrity and long-term stability of a repaired part are further guaranteed, preheating treatment can reduce the hardenability of a material, delay the cooling speed of a welding seam and promote release of hydrogen in the welding seam, and postweld heat treatment is beneficial to eliminating welding residual stress and the hydrogen embrittlement phenomenon.

Description

Technical Field

[0001] The invention relates to the technical field of coke tower repairing, in particular to a welding repairing method for an in-service coke tower. Background Art

[0002] Since the coke tower is subjected to long-term hot and cold fatigue, the two-phase temperature difference causes local plastic deformation. Long-term use will cause the tower body to swell, especially at the lap joints between the skirt and the cone head, where a large number of irregular cracks will appear. Factors such as the deterioration of raw materials and fluctuations in operating conditions may also cause cracks in the welds of the coke tower, and even penetration, causing high-temperature oil and gas leakage and safety accidents. The welding repair of the in-service coke tower refers to the process of repairing cracks, corrosion and other damage that occur during the use of the coke tower.

[0003] The existing repair methods for in-service coke towers have the following defects: First, the repair methods are less targeted; since the coke tower may suffer different degrees of damage during operation, the depth of its cracks and corrosion varies. The existing repair methods lack detailed consideration of the different damage depths and cannot accurately select suitable welding materials and repair methods for damage of different depths. This "one-size-fits-all" repair method is not only difficult to ensure the repair effect, but may also cause the mechanical properties of the repaired part to decrease due to the mismatch between the welding material and the parent material, thereby affecting the overall safety performance of the coke tower; Second, hydrogen embrittlement is prone to occur during welding. Hydrogen embrittlement is a phenomenon in which the mechanical properties of metal materials are reduced due to the absorption of hydrogen atoms during welding. One phenomenon is that during the repair process of the coke tower, if the welding process is not properly controlled, such as unreasonable settings of parameters such as welding current, voltage, and welding speed, or too much hydrogen in the welding material, hydrogen embrittlement may occur in the weld, which will not only reduce the strength and toughness of the weld, but may also cause brittle fracture of the weld, posing a serious threat to the safe operation of the coke tower; third, the repair quality of the composite layer is poor. With the development of coke tower manufacturing technology, more and more composite layer structures are used in its manufacturing process. The existing repair methods are less effective when facing composite layer damage. Due to the particularity of the composite layer structure, the material properties between different layers are quite different, and the interlayer bonding force is weak. Summary of the invention

[0004] The object of the present invention is to provide a welding repair method for an in-service coke drum to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for welding and repairing an in-service coke drum, comprising the steps of: damage assessment; material selection; surface treatment; preheating; welding repair; post-weld heat treatment; and quality inspection.

[0006] In the above step 1, the depth of the cracks in the coke drum is detected;

[0007] In the above step 2, suitable repair materials are selected for cracks of different depths;

[0008] In the above step 3, the crack area is subjected to surface treatment to facilitate subsequent repair welding;

[0009] In the above step 4, the welding area is preheated before welding to reduce the formation of thermal stress and cold cracks during welding;

[0010] In the above step 5, welding repair is performed according to the selected welding materials and welding process;

[0011] In the above step 6, the welding area is subjected to post-weld heat treatment to eliminate welding residual stress and hydrogen embrittlement;

[0012] In the above step seven, the weld repair area is visually inspected and non-destructively tested to ensure that the welding quality meets the standard requirements.

[0013] As a further technical solution of the present invention, in step one, an ultrasonic thickness gauge is used to measure the wall thickness of the coke drum to preliminarily determine the area that the crack may affect, and then a crack depth detector is used to accurately measure the crack and record information such as the depth, length, and position of the crack to provide a basis for subsequent material selection and repair strategies.

[0014] As a further technical solution of the present invention, in step 2, for single-layer 14Cr1MoR material, if the crack depth does not exceed 3 mm, NiCrMo-3 welding material is selected for repair, and if the crack depth exceeds 3 mm, R307B welding material is used for welding.

[0015] As a further technical solution of the present invention, in the step 2, for the composite layer structure, if the crack does not exceed the transition layer, NiCrFe-3 welding repair is adopted; if the crack depth reaches the base layer, R307B is first used for base layer repair welding, then NiCrFe-3 is used for transition layer repair welding, and finally the composite layer repair welding is performed.

[0016] As a further technical solution of the present invention, in step three, a grinder and a grinding wheel are used to thoroughly grind the crack area and the surrounding area to remove impurities such as oxide scale and oil stains to reveal the metallic luster, and then a cleaning agent is used to clean the polished area to ensure that the surface is clean and pollution-free.

[0017] As a further technical solution of the present invention, in the step 4, the core purpose of preheating before welding is to optimize the welding environment, reduce the hardenability of the material, slow down the cooling rate of the weld, promote the release of hydrogen in the weld, and reduce the welding stress, thereby effectively preventing the weld joint from producing delayed cracks. An adsorption electric heater is used as a preheating tool, and a computer temperature controller is equipped to accurately control the temperature. Before the welding operation, it is necessary to ensure that the groove and the area of ​​120 mm on both sides are preheated to a suitable temperature range of 150 to 230 ° C. During welding, the interlayer temperature must be maintained at the preheating temperature level and strictly not exceed 230 ° C. During the preheating operation, the width of the heating belt should be at least five times the wall thickness on both sides of the groove center, or at least 120 mm. At the same time, insulation measures are implemented within the range of 100 mm of the heating area and its extension. During the continuous heating process, the heater and the edge of the groove should maintain a suitable distance of about 20 mm. The temperature is measured by thermocouples during the preheating stage, and the temperature is continuously monitored with the help of infrared thermometers to ensure that the preheating process meets the preset requirements.

[0018] As a further technical solution of the present invention, in the step five, the welding operation is carried out in an order from the outside to the inside: first, the welding of the external groove is processed, then the internal groove is turned, and then the base layer is preheated, and then the base layer inside the tower is welded. When welding the inner side of the base layer, it is necessary to ensure that the weld and the base layer groove remain flat, and the protruding part is removed by grinding to avoid adverse effects on the subsequent composite welding quality.

[0019] As a further technical solution of the present invention, in step five, before performing composite layer welding, the base layer needs to be preheated again, and the preheating temperature needs to be maintained between 180°C and 220°C. At the same time, the interlayer temperature needs to be strictly controlled below 120°C. The arc starting and arc ending operations are completed in the repair welding area. When ending the arc, ensure that the arc pit is filled. When welding the transition layer, the thickness of the weld is kept within a relatively thin range, specifically 1.0 to 2.5 mm, to ensure that the quality of the surface corrosion-resistant layer is not reduced.

[0020] As a further technical solution of the present invention, in step six, after the base layer welding is completed, an electric heater is used to perform dehydrogenation treatment on the weld and the surrounding 120 mm area, and the treatment temperature is 380°C to 430°C for 2 hours. After the composite welding is completed, the weld must pass the quality inspection and enter the final heat treatment stage after passing the inspection. The temperature is controlled by an intelligent temperature control cabinet. The initial stage of heating is controlled below 350°C, and then the heating rate is limited to no more than 180°C per hour. After reaching 700°C, a constant temperature is maintained for 1.5 hours, and then the cooling rate is controlled to no more than 200°C per hour until the temperature drops below 350°C, and then natural cooling is performed. After the heat treatment is completed, the hardness of the parent material, weld and heat-affected zone of the repaired part is tested respectively to ensure that the hardness value does not exceed 250HB. At the same time, the weld surface is subjected to penetration testing, and the weld excess height is polished to be flat.

[0021] As a further technical solution of the present invention, in step seven, the weld is carefully inspected to ensure that there are no defects such as cracks and pores; non-destructive testing equipment is used to inspect the inside of the weld to ensure that the internal quality is good, and finally a mechanical property test is performed to verify whether performance indicators such as strength and toughness of the weld meet the requirements.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention designs a targeted repair method, which can select appropriate welding materials and repair technologies according to the specific depth and location of the crack. This targeted operation method ensures the accuracy and effectiveness of the repair work, improves the overall effect after the repair, and effectively eliminates the hydrogen embrittlement phenomenon that may occur during the welding process through measures such as preheating and post-weld heat treatment, further ensuring the structural integrity and long-term stability of the repaired part. The preheating treatment can reduce the hardenability of the material, slow down the cooling rate of the weld, and promote the release of hydrogen in the weld, while the post-weld heat treatment helps to eliminate welding residual stress and Hydrogen embrittlement phenomenon is eliminated to improve the toughness and strength of the weld. At the same time, a composite layer repair technology is designed. For the cracks in the composite layer, NiCrFe-3 welding materials are used for welding the transition layer. NiCrFe-3 welding materials have good corrosion resistance and high temperature strength, and can effectively form a good metallurgical bond with the base layer and the composite layer. Subsequently, R307B welding materials are combined for repair welding of the base layer and the composite layer. R307B welding materials have excellent welding performance and mechanical properties, and can meet the high requirements of composite layer repair for weld strength and toughness. The application of this composite layer repair technology not only improves the repair efficiency, but also significantly improves the quality level after repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Please see attached Figure 1 The present invention provides an embodiment: a method for welding and repairing an in-service coke drum, comprising the steps of: damage assessment; material selection; surface treatment; preheating; welding repair; post-weld heat treatment; quality inspection;

[0026] In the above step 1, an ultrasonic thickness gauge is used to measure the wall thickness of the coke drum to preliminarily determine the area that the crack may affect. Then, a crack depth detector is used to accurately measure the crack and record the depth, length, location and other information of the crack to provide a basis for subsequent material selection and repair strategies.

[0027] In the above step 2, for single-layer 14Cr1MoR material, if the crack depth does not exceed 3mm, NiCrMo-3 welding material is selected for repair; if the crack depth exceeds 3mm, R307B welding material is used for welding; for composite layer structure, if the crack does not exceed the transition layer, NiCrFe-3 welding is used for repair; if the crack depth reaches the base layer, R307B is first used for base layer repair welding, then NiCrFe-3 is used for transition layer repair welding, and finally composite layer repair welding is performed;

[0028] In the above step 3, a grinder and a grinding wheel are used to thoroughly grind the crack area and the surrounding area to remove impurities such as oxide scale and oil to reveal the metallic luster, and then a cleaning agent is used to clean the grinding area to ensure that the surface is clean and pollution-free;

[0029] Among them, in the above step 4, the core purpose of preheating before welding is to optimize the welding environment, reduce the hardenability of the material, slow down the cooling rate of the weld, promote the release of hydrogen in the weld, and reduce the welding stress, thereby effectively preventing delayed cracks in the weld joint. An adsorption electric heater is used as a preheating tool, and a computer temperature controller is equipped to accurately control the temperature. Before welding, it is necessary to ensure that the groove and the area of ​​120mm on both sides are preheated to a suitable temperature range of 150 to 230°C. During welding, the interlayer temperature must be maintained at the preheating temperature level and strictly not exceed 230°C. During the preheating operation, the width of the heating belt should be at least five times the wall thickness on both sides of the groove center, or at least 120mm. At the same time, insulation measures are implemented within the heating area and its extension of 100mm. During the continuous heating process, the heater and the edge of the groove should maintain a suitable distance of about 20mm. The temperature is measured by thermocouples during the preheating stage, and the temperature is continuously monitored with the help of infrared thermometers to ensure that the preheating process meets the preset requirements;

[0030] Among them, in the above step five, the welding operation follows the order from outside to inside: first process the welding of the external groove, then turn to the internal groove, then preheat the base layer, and then weld the base layer inside the tower. When welding the inner side of the base layer, it is necessary to ensure that the weld and the base groove remain flat, and the protruding part is removed by grinding to avoid adverse effects on the subsequent composite welding quality. Before composite welding, the base layer needs to be preheated again, and the preheating temperature needs to be maintained between 180°C and 220°C. At the same time, the interlayer temperature needs to be strictly controlled below 120°C. The arc starting and arc ending operations are completed in the repair welding area. When the arc is ended, it is ensured that the arc pit is filled. When welding the transition layer, the thickness of the weld is kept in a relatively thin range, specifically 1.0 to 2.5 mm, to ensure that the quality of the surface corrosion-resistant layer is not reduced;

[0031] In the above step six, the welding area is subjected to post-weld heat treatment to eliminate welding residual stress and hydrogen embrittlement. After the base welding is completed, the weld and the surrounding 120 mm area are subjected to dehydrogenation treatment using an electric heater. The treatment temperature is 380°C to 430°C for 2 hours. After the composite welding is completed, the weld must pass the quality inspection. After passing the inspection, it enters the final heat treatment stage. The temperature is controlled by an intelligent temperature control cabinet. The initial heating stage is controlled below 350°C. The heating rate is then limited to no more than 180°C per hour. After reaching 700°C, the constant temperature is maintained for 1.5 hours. The cooling rate is then controlled to no more than 200°C per hour until the temperature drops below 350°C, and then naturally cooled. After the heat treatment is completed, the hardness of the parent material, weld and heat-affected zone of the repaired weld is tested to ensure that the hardness value does not exceed 250HB. At the same time, the weld surface is subjected to penetration testing, and the weld excess height is polished to be flat.

[0032] In the above step seven, the weld is carefully inspected to ensure that there are no defects such as cracks and pores; non-destructive testing equipment is used to inspect the inside of the weld to ensure good internal quality; finally, mechanical properties testing is performed to verify whether performance indicators such as strength and toughness of the weld meet the requirements.

[0033] Based on the above, the advantages of the present invention are: the present invention designs a targeted repair strategy, which can accurately select the most matching welding material and repair technology according to the actual depth and precise position of the crack. This highly refined operation process not only ensures the high precision and effectiveness of the repair operation, but also greatly optimizes the overall effect after the repair. Through pretreatment and post-treatment measures, the present invention effectively avoids the potential risk of hydrogen embrittlement in the welding process, and provides a solid guarantee for the structural integrity and long-term stability of the repaired part. In the repair process, the preheat treatment can not only significantly reduce the hardenability of the material, but also effectively delay the cooling rate of the weld, thereby accelerating the escape process of hydrogen inside the weld, laying a good foundation for subsequent welding operations, and the post-weld heat treatment further consolidates the repair effect by eliminating the residual stress and The potential hydrogen embrittlement phenomenon significantly improves the toughness and strength of the weld. The present invention also incorporates composite layer repair technology. Aiming at the crack problem in the composite layer, NiCrFe-3 welding material is selected for welding of the transition layer. NiCrFe-3 welding material can easily achieve excellent metallurgical bonding with the base layer and the composite layer due to its excellent corrosion resistance and high temperature strength. On this basis, R307B welding material is combined to carry out the repair welding of the base layer and the composite layer. R307B welding material, with its excellent welding performance and mechanical properties, fully meets the stringent requirements of composite layer repair for weld strength and toughness. The application of this composite layer repair technology not only significantly improves the efficiency of the repair operation, but also improves the quality level after repair. Through this series of designs and measures, the present invention provides strong technical support and guarantee for the long-term safe operation of equipment such as coke towers in service.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A welding repair method for an in-service coke drum, comprising step 1, damage assessment; step 2, material selection; step 3, surface treatment; step 4, preheating treatment; step 5, welding repair; step 6, post-weld heat treatment; step 7, quality inspection; characterized in that: In the above step 1, the depth of the cracks in the coke drum is detected; In the above step 2, suitable repair materials are selected for cracks of different depths; In the above step 3, the crack area is subjected to surface treatment to facilitate subsequent repair welding; In the above step 4, the welding area is preheated before welding to reduce the formation of thermal stress and cold cracks during welding; In the above step 5, welding repair is performed according to the selected welding materials and welding process; In the above step 6, the welding area is subjected to post-weld heat treatment to eliminate welding residual stress and hydrogen embrittlement; In the above step seven, the weld repair area is visually inspected and non-destructively tested to ensure that the welding quality meets the standard requirements.

2. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step 1, an ultrasonic thickness gauge is used to measure the wall thickness of the coke drum to preliminarily determine the area that the crack may affect, and then a crack depth detector is used to accurately measure the crack and record information such as the depth, length, and location of the crack to provide a basis for subsequent material selection and repair strategies.

3. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step 2, for the single-layer 14Cr1MoR material, if the crack depth does not exceed 3 mm, NiCrMo-3 welding material is selected for repair, and if the crack depth exceeds 3 mm, R307B welding material is used for welding.

4. The welding repair method for an in-service coke drum according to claim 3, characterized in that: In the step 2, for the composite layer structure, if the crack does not exceed the transition layer, NiCrFe-3 welding repair is used; if the crack depth reaches the base layer, R307B is first used for base layer repair welding, then NiCrFe-3 is used for transition layer repair welding, and finally the composite layer is repaired.

5. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step three, a grinder and a grinding wheel are used to thoroughly grind the crack area and the surrounding area to remove impurities such as oxide scale and oil to reveal the metallic luster, and then a cleaning agent is used to clean the grinded area to ensure that the surface is clean and pollution-free.

6. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step 4, the core purpose of preheating before welding is to optimize the welding environment, reduce the hardenability of the material, slow down the cooling rate of the weld, promote the release of hydrogen in the weld, and reduce the welding stress, thereby effectively preventing the weld joint from producing delayed cracks. An adsorption electric heater is used as a preheating tool, and a computer temperature controller is equipped to accurately control the temperature. Before the welding operation, it is necessary to ensure that the groove and the area of ​​120 mm on both sides are preheated to a suitable temperature range of 150 to 230 ° C. During welding, the interlayer temperature must be maintained at the preheating temperature level and strictly not exceed 230 ° C. During the preheating operation, the width of the heating belt should be at least five times the wall thickness on both sides of the groove center, or at least 120 mm. At the same time, insulation measures are implemented within the range of 100 mm of the heating area and its extension. During the continuous heating process, the heater and the edge of the groove should maintain a suitable distance of about 20 mm. The temperature is measured by thermocouples during the preheating stage, and the temperature is continuously monitored with the help of infrared thermometers to ensure that the preheating process meets the preset requirements.

7. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step 5, the welding operation is carried out in an order from the outside to the inside: first, the welding of the external groove is processed, then the internal groove is turned, and then the base is preheated, and then the base inside the tower is welded. When welding the inner side of the base, it is necessary to ensure that the weld and the base groove remain flat, and the protruding part is removed by grinding to avoid adverse effects on the subsequent composite welding quality.

8. The welding repair method for an in-service coke drum according to claim 7, characterized in that: In the step five, before the composite layer welding, the base layer needs to be preheated again, and the preheating temperature needs to be maintained between 180°C and 220°C. At the same time, the interlayer temperature needs to be strictly controlled below 120°C. The arc starting and arc ending operations are completed in the repair welding area. When the arc is ended, the arc pit is filled. When welding the transition layer, the thickness of the weld is kept within a relatively thin range, specifically 1.0 to 2.5 mm, to ensure that the quality of the surface corrosion-resistant layer is not reduced.

9. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In the step six, after the base layer welding is completed, an electric heater is used to perform dehydrogenation treatment on the weld and the surrounding 120 mm area, and the treatment temperature is 380°C to 430°C for 2 hours. After the composite welding is completed, the weld must pass the quality inspection, and enter the final heat treatment stage after passing the inspection. The temperature is regulated by an intelligent temperature control cabinet, and the initial heating stage is controlled below 350°C. The heating rate is then limited to no more than 180°C per hour. After reaching 700°C, a constant temperature is maintained for 1.5 hours, and then the cooling rate is controlled to no more than 200°C per hour until the temperature drops below 350°C, and then natural cooling is performed. After the heat treatment is completed, the hardness of the parent material, weld and heat-affected zone of the repaired weld is tested respectively to ensure that the hardness value does not exceed 250HB. At the same time, the weld surface is subjected to penetration testing, and the weld excess height is polished to be flat.

10. The welding repair method for an in-service coke drum according to claim 1, characterized in that: In step seven, the weld is carefully inspected to ensure that there are no defects such as cracks and pores; non-destructive testing equipment is used to inspect the inside of the weld to ensure that the internal quality is good, and finally a mechanical property test is performed to verify whether performance indicators such as strength and toughness of the weld meet the requirements.

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