CN110405375B

CN110405375B - Method for repairing residual cracks by welding double transition layers

Info

Publication number: CN110405375B
Application number: CN201910721746.4A
Authority: CN
Inventors: 李丽丹; 潘子祥; 朱宁; 鲁晓欣
Original assignee: Pangang Group Engineering Technology Co Ltd
Current assignee: Pangang Group Engineering Technology Co Ltd
Priority date: 2019-08-06
Filing date: 2019-08-06
Publication date: 2021-08-24
Anticipated expiration: 2039-08-06
Also published as: CN110405375A

Abstract

The invention discloses a method for repairing residual cracks by welding a double transition layer, relates to the technical field of welding repair of cracks generated by steel equipment parts, and solves the technical problem of providing a method for welding and repairing welding seams which cannot clean cracks generated by the steel equipment parts. The technical scheme adopted by the invention is as follows: the method for repairing residual cracks by welding the double transition layers comprises the following steps: s1 removing the bevel face and two sides of the welding seam; s2, heat-insulating the high-nickel welding rod (the nickel mass fraction is more than or equal to 90%) and the austenitic welding rod for standby; s3 preheating the groove and two sides; s4, selecting a high-nickel welding rod to weld a high-nickel transition layer at a crack, and selecting an austenite welding rod with higher strength than the high-nickel transition layer and a parent metal to weld a reinforcing layer on the high-nickel transition layer; s5 heating and heat preservation after welding; and S6, after cooling the welding line to room temperature, polishing the fusion part of the welding line and the parent metal. The method is suitable for welding repair of welding seams which cannot be cleaned up by cracks generated by all steel equipment.

Description

Method for repairing residual cracks by welding double transition layers

Technical Field

The invention relates to the technical field of welding repair of cracks generated by steel equipment, in particular to a method for welding and repairing a welding seam with cracks which cannot be cleaned completely.

Background

The 1250 ton brick press body is made of 35 cast steel, and one side of the hydraulic cylinder generates a fatigue crack with the length of 320mm due to long-term overload dynamic load use, so that the brick press body cannot be used continuously and needs to repair the crack. When the defect depth is cleaned to 120mm depth by using a carbon arc air gouging machine and an angle grinder, crack defects exist, and the crack defects cannot be continuously cleaned due to the fact that the distance between the crack defects and the hydraulic cylinder is too close. If the cracks are not completely removed, the welding line is welded normally, residual crack defects exist in the welding line, if equipment is operated and used, the residual cracks can extend to fracture under the action of load for hours or days, and equipment scrapping and large economic loss are caused. At present, under the condition that crack defects cannot be eliminated, back plates are additionally arranged on the front side and the back side of the crack, and holes are drilled for riveting or bolt penetrating for fastening. Because the back of the crack of the brick pressing machine body is provided with the hydraulic cylinder, and the front surface has irregular radian, a method of additionally installing a back plate cannot be adopted, so that the crack can be repaired only by a new welding mode.

In the welding process, a double-transition layer welding method is provided, which mainly aims at preventing intermetallic brittle compounds and cracks from being generated in welding seams when dissimilar metal materials are welded.

The tissue and performance of a TiNi/NiCrMo double-transition-layer fusion welding butt joint for a TA1/X80 composite plate (Wuweigang et al, the journal of Material research, 2016, volume 30, No. 5) relates to a double-transition-layer welding research, and when the transition layers in the TiA1/X80 composite plate are welded, the thermal-physical performance difference of Ti and Fe is large, and a large amount of hard and brittle intermetallic compounds, low-melting-point eutectic and carbide are easily formed in a welding seam, so that the welding seam is easily brittle. Starting from a fusion welding non-uniform temperature field, the problems of difficult metallurgical bonding of titanium and steel, poor interface adaptation and tissue matching of a composite board and the like are analyzed, a fusion welding butt joint experiment is carried out on the titanium-steel composite board by adopting TiNi and NiCrMo as welding materials of a transition layer, the characteristics of evolution and component change of the structure of each layer of welding seams of the welding joint are analyzed, the phases of the welding seams of the transition layer are analyzed, and the composite board welding joint with better mechanical property is obtained. The study of this paper shows that: the main problems of titanium and steel welding are analyzed, TiNi and NiCrMo are respectively adopted as welding materials of the welding double transition layers, so that the welding seams of the transition layers are well fused, intermetallic brittle compounds and the like are not easy to generate, and the welding seam quality of the titanium-steel composite plate and the mechanical property of a welding joint can be ensured.

"double-layer transition arc butt welding of a high manganese steel frog and a steel rail" (invigh et al, journal of welding 1999 12 months) is another article on double-transition layer welding, and the article analyzes that when the high manganese steel and the steel rail are welded by arc welding, defects such as liquefied cracks and carbide precipitation are easy to generate in a heat affected zone of the high manganese steel, and martensite is easy to generate in the heat affected zone of the steel rail. If the forced forming electric arc welding is firstly used at one side of the high manganese steel rail, two welding materials are adopted to weld the transition layer: the bottom of the rail is welded by a high manganese steel welding rod, the rail web and the rail head are welded by a double transition layer welded by a self-protection flux-cored wire, then the high manganese steel rail and the steel rail are butt-welded, and the static bending test value of the joint is improved. And the developed welding material of the transition layer is combined with the forced forming electric arc welding process to firstly build up the transition layer on one side of the high manganese steel frog, and then the transition layer is subjected to butt welding test with the steel rail, so that the static bending test value of the joint is improved, and the comprehensive performance is improved. Therefore, when the high manganese steel frog is welded with the steel rail, the method of firstly overlaying two transition layer welding materials on one side can prevent the defects of liquefied cracks, carbide precipitation, martensite structures and the like of a welded joint and improve the static bending test value and the like of the joint.

The research on bead weld repair of semisteel rollers (the thesis of Master's academic position of Tianjin university, Wu-said, 2002, 12 months) literature analyzes that semisteel rollers are a material between steel and iron, and have high carbon content, so the largest technical problem of bead weld repair is the problem of cracks. The research utilizes the good toughness of stainless steel, designs a stainless steel flux-cored wire 02# to build up a first transition layer, and then utilizes a low-carbon YD404L-4 flux-cored wire with an alloy system consistent with the welding wire of the working layer to build up a second transition layer, so that the problem of cracks in welding high-carbon semisteel is thoroughly and effectively solved. According to the research, a stainless steel flux-cored wire with good plasticity is adopted to weld a first transition layer on a semi-steel roller in an overlaying mode, so that the first welding transition layer has good toughness; and then overlaying a second transition layer flux-cored wire which is the same as the working layer alloy system on the basis of the first transition layer, so that the problem of cracks caused by directly overlaying an alloy wire which is consistent with the working layer on the semi-steel roller can be solved.

From the above analysis, it is found that the conventional double-transition layer welding method including the above-mentioned document is not suitable for welding repair of defects that cannot be cleaned of cracks, in terms of selection of welding materials, and the effect and purpose of overlaying the double-transition layer.

Disclosure of Invention

The invention aims to solve the technical problem of providing a double-transition-layer welding repair method for welding repair under the condition that cracks generated by steel equipment parts cannot be completely removed.

The technical scheme adopted by the invention for solving the technical problems is as follows: the method for repairing residual cracks by welding the double transition layers is used for welding and repairing the condition that steel equipment parts have cracks and cannot be cleaned completely, and comprises the following steps:

s1, removing the bevel face and two sides of the welding seam; specifically, the method comprises the following steps: and step S1, removing water, rust and oil impurities on the bevel face of the welding seam and within 10-15 mm of the two sides of the bevel face of the welding seam.

S2, keeping the temperature of the high-nickel welding rod and the austenite welding rod with the nickel mass fraction of more than or equal to 90% for standby; specifically, the method comprises the following steps: in step S2, the heat preservation temperature of the high-nickel welding rod is 100-150 ℃.

S3, preheating the groove and two sides; specifically, the method comprises the following steps: in step S3, the groove and both sides are uniformly preheated to 200-250 ℃ within a range of 200-300 mm.

S4, selecting a high-nickel welding rod to weld a high-nickel transition layer at a crack, and selecting an austenite welding rod with higher strength than the high-nickel transition layer and a parent metal to weld a reinforcing layer on the high-nickel transition layer;

specifically, the method comprises the following steps: in the step S4, the high-nickel transition layer and the reinforcing layer are welded in a welding sequence of a segmented back welding method, the length of each segment is controlled to be 60-100 mm, and the joint position is staggered by at least 20 mm;

further, the method comprises the following steps: in the step S4, in the welding process of the high-nickel transition layer and the reinforcement layer, each welding rod is immediately hammered by a hammer with a round head, the middle of the welding bead is hammered, and then the fusion part of the welding bead and the base metal is hammered, so that the surface of the welding bead is covered with pits.

Further, the method comprises the following steps: in step S4, the filling and cover welding should be controlled so that the interlayer temperature is not lower than the preheating temperature.

Specifically, the method comprises the following steps: in step S4, the thickness of the high nickel transition layer is 4-6 mm, and the thickness of the reinforcing layer is 5-7 mm.

S5, heating and preserving heat after welding; specifically, the method comprises the following steps: in step S5, immediately heating to 300-350 ℃ after welding, and preserving heat for 1-2 h.

And S6, after cooling the welding line to room temperature, polishing the fusion part of the welding line and the base material. Specifically, the method comprises the following steps: in the step S6, grinding the fusion position of the welding line and the base metal by an angle grinder to enable the fusion position to be in smooth transition; or the welding seam is grinded to be flush with the base material.

The method for repairing the residual cracks by welding the double transition layers includes the steps of overlaying the high-nickel transition layer and the reinforcing layer at the positions of the cracks which are not cleaned completely respectively to form the double transition layers, wherein the high-nickel transition layer is beneficial to improving the plasticity and the toughness of welding seams at the positions with the residual cracks, reducing the sensitivity of steel to gaps, improving the solubility of hydrogen in deposited metal, absorbing more stress at the positions with the cracks and reducing stress concentration. The reinforcing layer has a reinforcing effect on the high-nickel transition layer, and can prevent the high-nickel transition layer from being pulled and cracked under the action of large external force or tensile stress. The reinforcement layer serves to control the extension of the residual cracks and prevent the generation of new cracks.

The method for repairing the residual cracks by welding the double transition layers has the beneficial effects that: the invention has simple equipment and machines, is convenient for learning and easy to master, can effectively reduce the stress and stress concentration at the residual crack and prevent the residual crack from extending due to tensile stress. The invention can ensure the capability of bearing load and resisting fatigue of the welding seam with residual cracks at the root of the welding seam, prevent the residual cracks from extending and generating new cracks again, thereby ensuring the performance and the use requirement of the welding seam and filling the technical blank that the welding repair can not be directly carried out under the condition that the cracks are not completely removed in China. The method is suitable for welding repair under the condition that cracks generated by all steel equipment pieces cannot be cleaned, and has a wide application prospect.

Drawings

FIG. 1 is a schematic diagram showing the positional relationship among cracks, transition layers and reinforcing layers in the present invention.

Reference numerals: crack 1, high nickel transition layer 2, reinforcing layer 3.

Detailed Description

The invention will be further explained with reference to the drawings.

Referring to fig. 1, the method for repairing residual cracks by welding a double transition layer is used for welding and repairing the condition that a steel equipment part has cracks 1 and cannot be cleaned completely, and comprises the following steps:

s1, removing impurities such as water, rust and oil in the groove face of the welding seam and 10-15 mm of two sides before welding.

S2, drying the high-nickel welding rod and the austenitic welding rod according to the specification, and placing the high-nickel welding rod and the austenitic welding rod in a heat-preserving container at 100-150 ℃ for later use. Wherein the high nickel welding rod refers to a welding rod with the nickel mass fraction being more than or equal to 90 percent.

And S3, preheating the groove and two sides. For example, the groove and both sides are uniformly preheated to 200 to 250 ℃ within a range of 200 to 300mm, and the purpose of preheating is to reduce the cooling rate of the welded joint and prevent the occurrence of crystal cracks or hardened structures.

S4, selecting a high-nickel welding rod to weld the high-nickel transition layer 2 at the position with the crack 1 to obtain a first transition layer; and then selecting an austenite welding rod with higher strength than the high-nickel transition layer 2 and the parent metal to weld the reinforcing layer 3 on the high-nickel transition layer 2 to obtain a second transition layer, as shown in figure 1. The high-nickel transition layer 2 can absorb more stress at the crack 1, reduce the sensitivity of steel to gaps and improve the solubility of hydrogen in deposited metal. Specifically, the thickness of the transition layer is controlled to be 4-6 mm, for example 5 mm. The reinforcing layer 3 has a reinforcing effect on the upper layer, namely the high nickel transition layer 2, and prevents the metal of the high nickel transition layer 2 from being pulled apart due to large external force or tensile stress. Specifically, the thickness of the reinforcing layer 3 is controlled to be 5-7 mm, for example 6 mm.

The welding process of the high nickel transition layer 2 and the reinforcing layer 3 adopts a welding sequence of a segmented back welding method, the length of each segment is controlled within the range of 60-100 mm, so that the stress is reduced and distributed uniformly, and the joints in the midway are staggered by at least 20 mm. In the welding process of the high-nickel transition layer 2 and the reinforcing layer 3, each welding rod is welded, a hammer with a round head is used for hammering a welding bead immediately, for example, the hammer is 0.5kg in weight, the diameter R of the round head is 5mm, the middle of the welding bead is hammered, then the fusion part of the welding bead and a base metal is hammered, so that the surface of the welding bead is full of pits, crystal grains on the surface of the welding bead are crushed, and partial stress is eliminated and tensile stress is changed into compressive stress. The temperature between the filling layer and the cover layer is controlled to be equal to or slightly higher than the preheating temperature so as to prevent the generation of coarse structures due to overhigh temperature and reduce the ductility and toughness of the welding seam.

The present invention differs from conventional double transition layer welding in that the choice of welding material, and the function and purpose of the double transition layer are explained below. On one hand, in terms of the selection of welding materials, the principle of selecting welding materials in the existing double-transition layer welding is as follows: can be well fused with two metals with different properties, the transition layers also need to be well fused, and the performance requirement of the welding seam at the connecting part can be ensured. For welding of two different metal materials, the selected double transition layer materials are different. The selected welding materials are high-nickel welding rods and austenite welding rods, are used for welding repair aiming at cracks generated by steel equipment, and are fixed. On the other hand, on the effect and the purpose of the surfacing double transition layer, the effect that the double transition layer is adopted in the existing double transition layer welding is as follows: the method avoids the phenomenon that the plasticity and the toughness of the weld metal are seriously reduced and the weld metal becomes brittle or the weld overlay metal cracks and the like due to intermetallic compounds generated when two metals with larger performance difference are fused together. The purpose of the dissimilar metal transition is to enable metal materials at two sides to be closer to a parent metal, enable a welding material to be well fused with the parent metal and enable intermetallic compounds not to be generated between deposited metals; namely, two metals with larger performance difference are combined together by a method of connecting the transition layers in the middle through the double transition layers between the welding seams, thereby meeting the mechanical performance requirement of the welding seams and preventing the welding seams or the overlaying layers from generating cracks. The invention adopts double transition layers to have the following functions: the high-nickel welding rod is selected to weld the first layer (the high-nickel transition layer 2), so that the plasticity and the toughness of the welding line at the position with the residual cracks are improved, the sensitivity of steel to gaps is reduced, the solubility of hydrogen in deposited metal is improved, more stress at the position with the cracks can be absorbed, the plasticity of the overlaying layer is improved, and the stress concentration is reduced; however, the high nickel transition layer 2 has a low strength. The second layer (reinforcing layer 3) is welded by adopting an austenite welding rod with the strength higher than that of the base material and the high-nickel transition layer 2, so that the first layer (high-nickel transition layer 2) is reinforced, and the tensile crack caused by the action of large external force or tensile stress can be prevented. The purpose is to control the extension of residual cracks and to prevent the generation of new cracks.

And S5, heating after welding and keeping the temperature. Particularly, for steel equipment parts with hardening tendency, post heat treatment after welding should be noticed, for example, post heat treatment for immediately heating the steel equipment parts with hardening tendency to 300-350 ℃ after welding and keeping the temperature for 1-2 h. The post-weld heat treatment can reduce part of residual stress and eliminate hydrogen content in the welded joint, and prevent cold cracks.

And S6, after cooling the welding line to room temperature, polishing the fusion part of the welding line and the base material. After the welding line is cooled to room temperature, grinding the fusion position of the welding line and the base metal by using an angle grinder to enable the fusion position to be in smooth transition; if bearing dynamic load, should repair the welding seam and grind to be level with the base metal, prevent to appear stress concentration and produce fatigue crack.

The practice of welding repair at the crack of 1250-ton brick pressing machine body (made of 35 cast steel) verifies that the welding quality and the service performance of the welding seam meet the requirements, and the method for welding repair of residual cracks by using the double transition layers has the advantages of simple equipment, flexible and convenient operation, easy mastering and suitability for popularization.

Claims

1. The method for repairing residual cracks by welding the double transition layers is used for welding and repairing cracks (1) generated on steel equipment and cracks which cannot be cleaned up, and is characterized in that: the method comprises the following steps:

s1, removing the bevel face and two sides of the welding seam;

s2, keeping the temperature of the high-nickel welding rod and the austenite welding rod with the nickel mass fraction of more than or equal to 90% for standby;

s3, preheating the groove and two sides;

s4, selecting a high-nickel welding rod to weld a high-nickel transition layer (2) at the position with the crack (1), selecting an austenite welding rod with higher strength than the high-nickel transition layer (2) and the parent metal to weld a reinforcing layer (3) on the high-nickel transition layer (2), and forming a double transition layer by the high-nickel transition layer (2) and the reinforcing layer (3); welding the filling and covering layers;

s5, heating and preserving heat after welding;

and S6, after cooling the welding line to room temperature, polishing the fusion part of the welding line and the base material.

2. The method for double transition layer weld repair of residual cracks of claim 1, wherein: and step S1, removing water, rust and oil impurities on the bevel face of the welding seam and within 10-15 mm of the two sides of the bevel face of the welding seam.

3. The method for double transition layer weld repair of residual cracks of claim 1, wherein: in step S2, the heat preservation temperature of the high-nickel welding rod is 100-150 ℃.

4. The method for double transition layer weld repair of residual cracks of claim 1, wherein: in step S3, the groove and both sides are uniformly preheated to 200-250 ℃ within a range of 200-300 mm.

5. The method for repairing residual cracks by welding the double transition layers according to any one of claims 1 to 4, wherein: in the step S4, the high-nickel transition layer (2) and the reinforcing layer (3) are welded in a welding sequence by adopting a segmented back welding method, the length of each segment is controlled to be 60-100 mm, and the joint position is staggered by at least 20 mm.

6. The method for double transition layer weld repair of residual cracks of claim 5, wherein: in the step S4, in the welding process of the high-nickel transition layer (2) and the reinforcing layer (3), each welding rod is welded, a hammer with a round head is used for hammering a welding bead immediately, the middle of the welding bead is hammered, and then the fusion part of the welding bead and a base metal is hammered, so that the surface of the welding bead is fully covered with pits.

7. The method for double transition layer weld repair of residual cracks of claim 6, wherein: in step S4, the filling and cover welding should be controlled so that the interlayer temperature is not lower than the preheating temperature.

8. The method for double transition layer weld repair of residual cracks of claim 5, wherein: in step S4, the thickness of the high nickel transition layer (2) is 4-6 mm, and the thickness of the reinforcing layer (3) is 5-7 mm.

9. The method for repairing residual cracks by welding the double transition layers according to any one of claims 1 to 4, wherein: in step S5, immediately heating to 300-350 ℃ after welding, and preserving heat for 1-2 h.

10. The method for repairing residual cracks by welding the double transition layers according to any one of claims 1 to 4, wherein: in the step S6, grinding the fusion position of the welding line and the base metal by an angle grinder to enable the fusion position to be in smooth transition; or the welding seam is grinded to be flush with the base material.