CN113881988A - Preparation method of water-cooled wall heating surface induction fusion welding and brush plating composite coating - Google Patents

Abstract

The invention discloses a preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating, which comprises the following steps; preparing a nickel-based self-fluxing alloy spraying powder material and a nickel-based nano ceramic composite plating solution; step (2), carrying out sand blasting and coarsening treatment on the heating surface of the water wall tube bank by an automatic sand blasting machine; step (3), preparing a nickel-based self-fluxing alloy coating with the thickness of 0.5 +/-0.1 mm by flame spraying on the surface of the tube bank; step (4), performing high-frequency induction remelting on the spray coating; step (5), strictly controlling the deformation of the tube bank by adopting a special tool in the induction remelting process; step (6), performing brush plating on the tube top, wherein the thickness is 0.05-0.08 mm; and (7) detecting the quality of the composite coating on the surface of the tube bank, and manually repairing the local defects. The invention carries out double-layer reinforcement on the top part of the tube, and the prepared composite coating is suitable for being applied to the parts with the worst working conditions and the highest tube explosion probability in the boiler.

Description

Preparation method of water-cooled wall heating surface induction fusion welding and brush plating composite coating

Technical Field

The invention relates to the technical field of coating preparation, in particular to a preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating.

Background

Along with the accelerated implementation of the national strategy for developing new energy, the domestic waste incineration power generation industry develops rapidly in recent years, and the bottleneck problem which restricts the technical development of waste incineration power generation at present is that the high-temperature corrosion of the heating surfaces of four tubes of a boiler is serious, the tube explosion phenomenon is caused by the reduction of corrosion, accidents not only seriously threaten the safety of personnel and equipment, but also cause the unplanned production halt to be increasingly frequent for maintenance, and the influence on economic benefit is serious, so that the development of the waste incineration power generation industry is greatly influenced;

the coating protection is the most effective protection method for high-temperature corrosion, the most applied coating protection for many years is the inconel625 alloy surfacing method, the method is known as the most reliable protection technology with the longest protection life (up to 10 years) at present, but the defects are low efficiency and high cost, and a plurality of middle and small boiler manufacturers are difficult to bear, 2017 firstly adopts a composite method of flame spraying nickel-based self-fluxing alloy and high-frequency induction remelting to prepare a coating on the surface of a heating surface of a water wall, the application effect is better in a high-temperature corrosion environment of a boiler for several years, the performance and service life of the coating are close to those of surfacing (6-8 years), and the preparation efficiency and cost are both superior to that of surfacing, so the coating is generally favored by the industry and has good development momentum;

at present, surfacing is the most reliable and mature method in all coating protection, but the cost is high, and each square meter exceeds 1.4 ten thousand yuan, for example, when a protective coating is made on the heating surface of a boiler water wall, the protective coating is generally thousands of square meters, the protection cost of tens of millions is prosperous for many medium and small enterprises, and the protection life of the induction fusion welding method is close to that of surfacing but has a certain difference.

Disclosure of Invention

The invention aims to provide a preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating, which aims to solve the problems in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating comprises the following steps;

preparing a nickel-based self-fluxing alloy spraying powder material and a nickel-based nano ceramic composite plating solution;

step (2), carrying out sand blasting and coarsening treatment on the heating surface of the water wall tube bank by an automatic sand blasting machine;

step (3), preparing a nickel-based self-fluxing alloy coating with the thickness of 0.5 +/-0.1 mm by flame spraying on the surface of the tube bank;

step (4), performing high-frequency induction remelting on the spray coating;

step (5), strictly controlling the deformation of the tube bank by adopting a special tool in the induction remelting process;

step (6), performing brush plating on the tube top, wherein the thickness is 0.05-0.08 mm;

and (7) detecting the quality of the composite coating on the surface of the tube bank, and manually repairing the local defects.

Preferably, in step (6), pretreatment before brush plating is required:

s21, brushing electric cleaning liquid, connecting an electrode positively, enabling the working voltage to be 8-10V, brushing and plating the pipe row surface to generate milky bubbles to achieve an oil removing effect, and washing with clear water;

s22, brush plating of an activating solution, connecting a negative electrode with a working voltage of 10-12V, activating until a plated part is black, generating carbon black and dirt on the surface, and washing with clear water.

Preferably, in the step (6), the brush plating method specifically comprises:

s31, firstly plating a priming layer, namely firstly plating a layer of special nickel priming, wherein the special nickel has the function of improving the bonding strength of a plating layer and a base material, the brushing plating time is specifically based on the size of a workpiece, under general conditions, a light green plating layer appears on the surface of the workpiece, and the brushing plating voltage is 14-16V;

s32, plating a working layer, plating a nickel-based nano ceramic composite plating solution, positively connecting an electrode, and brushing the plating voltage to 12-15V.

Preferably, the preparation method of the nickel-based nano ceramic composite plating solution comprises the following steps:

adding proper amount of ZrO into nickel plating basic solution₂/Al₂O₃/NiCr-Cr₂C₃Nano ceramic powder to obtain nickel-base nano ceramic ZrO₂/Al₂O₃/NiCr-Cr₂C₃Brush plating of composite coating, ZrO₂/Al₂O₃/NiCr-Cr₂C₃The nano particles not only improve the high-temperature corrosion resistance, but also can inhibit the growth of coating crystal grains at high temperature to enable ZrO₂/Al₂O₃/NiCr-Cr₂C₃Adding the particles into the quick nickel brush plating solution according to the proportion of 10-15g/L, firstly magnetically stirring the prepared composite plating solution at constant temperature for 30min, then oscillating the composite plating solution for 30min by ultrasonic waves, and taking graphite as an anode and a water wall tube bank as a cathode in the brush plating.

The preparation method of the water-cooled wall heating surface induction fusion welding and brush plating composite coating has the beneficial effects that:

1. the prepared composite coating is suitable for being applied to the parts with the worst working condition and the highest pipe explosion probability in the boiler, such as the middle upper part and the ceiling of a water-cooled wall of a first flue, a second flue, a high-parameter boiler and the like, by performing double-layer reinforcement on the top part of the pipe;

2. compared with pure fusion welding, the composite coating prepared by the invention is only improved by less than 8 percent, the operation cost is mainly the consumption of a brush plating solution and a plating pen (no calculation of disposable equipment investment, about 300 yuan/square meter), the preparation efficiency is higher than that of integral surfacing by more than 30 percent, most importantly, after the tube top of the water wall tube bank is subjected to double-layer reinforcement, the worries of tube explosion of a garbage power station can be avoided, and the service life is basically equivalent to that of complete surfacing;

3. the invention adopts the process of preparing the composite coating by adopting the nickel-based nano ceramic for brush plating, in order to provide the brush plating efficiency, although more than ten pieces of brush plating equipment are required to be put into one time, the equipment only has 3000 plus 5000 yuan/piece, has small volume, light weight and simple operation, and simultaneously, the material cost of plating solution, plating pens and other consumables is very low, so the invention is easy to realize for manufacturers of induction fusion welding coatings.

Drawings

FIG. 1 is a schematic diagram of a photograph of a water wall according to the present invention;

FIG. 2 is a schematic diagram of the structure of a waterwall of the present invention;

FIG. 3 is a tube explosion diagram of the heating surface of the boiler tube according to the present invention;

FIG. 4 is a schematic view of a flare of the present invention;

FIG. 5 is a graphical representation of the burst cross-sectional wall thickness data of the present invention;

FIG. 6 is a schematic view of the brush plating and induction fusion welding composite coating on the top of a tube according to the present invention;

FIG. 7 is a schematic view of brush plating according to the present invention;

FIG. 8 is a schematic view of the brush plating tube top of the present invention;

FIG. 9 is a schematic view of the initial position of brush plating according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In embodiment 1, please refer to fig. 1 to 9, the present invention provides a technical solution: a preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating comprises the following steps;

preparing a nickel-based self-fluxing alloy spraying powder material and a nickel-based nano ceramic composite plating solution;

step (2), carrying out sand blasting and coarsening treatment on the heating surface of the water wall tube bank by an automatic sand blasting machine;

step (3), preparing a nickel-based self-fluxing alloy coating with the thickness of 0.5 +/-0.1 mm by flame spraying on the surface of the tube bank;

step (4), performing high-frequency induction remelting on the spray coating;

step (5), strictly controlling the deformation of the tube bank by adopting a special tool in the induction remelting process;

step (6), performing brush plating on the tube top, wherein the thickness of the tube top is 0.05 mm;

pretreatment before brush plating is required: s21, brushing electric cleaning liquid, connecting an electrode positively, applying a working voltage of 10V, brushing and plating the surface of the tube bank to generate milky bubbles to achieve an oil removing effect, and washing with clear water; s22, brush plating an activating solution, connecting a negative electrode with a working voltage of 11V, activating until a plated part is black, generating carbon black and dirt on the surface, and washing with clear water;

the specific method of brush plating comprises the following steps: s31, firstly plating a priming layer, namely firstly plating a layer of special nickel for priming, wherein the special nickel has the function of improving the bonding strength of a plating layer and a base material, the brushing plating time is specifically based on the size of a workpiece, under general conditions, a light green plating layer appears on the surface of the workpiece, and the brushing plating voltage is 15V; s32, plating a working layer, plating a nickel-based nano ceramic composite plating solution, positively connecting an electrode, and brushing a plating voltage of 14V;

and (7) detecting the quality of the composite coating on the surface of the tube bank, and manually repairing the local defects.

As shown in figures 1 and 2, the external structure of the remelting coil is formed by fixedly connecting a plurality of copper pipes with closed rectangular sections, wherein the four sides connected side by side are all planes, the coil is fixed during remelting, and the pipe row is fed forwards under the traction of a lower transmission chain.

As shown in FIG. 3, the summary and summary of the topographical features of the boiler waterwalls and superheater coils is shown, with almost all of the ports located in the vicinity of the tube tips on the fired side of the waterwall tubes and superheater.

As shown in figures 4 and 5, the water wall is tested to the fire side bursting opening, the wall thickness near the bursting opening is found to be seriously reduced from 7mm to 2.94-4mm, the local wall thickness is reduced by 4mm, after the water wall is actually measured to be in service for 2 years, the wall thickness is reduced at the two sides of the tube top most rapidly, the thinnest part is less than 3mm, the possibility of tube bursting exists at any time, tube bursting does not occur at some parts with the most serious reduction, the local structural characteristics are found through comparison and analysis, the difference of the outer wall diameter is large, the change of the inner wall diameter is small, and the conditions at the tube bursting position are just opposite, thereby the tube bursting is mainly caused by the tube wall reduction caused by the outer wall corrosion, in addition, even for the same reduction caused by the outer wall corrosion, the wall thickness near the combination part of some water wall tube roots and the fins is found through detection, the tube top is of a convex structure and is relatively nearest to high-temperature flue gas of a hearth, the tube root part (including a fin) is of a concave structure, the contact surface for receiving hearth radiation heat and high-temperature soot is obviously smaller due to shielding of the part close to the tube top, and the damage to the surface material of the outer wall of the tube, including microcracks caused by pitting corrosion, soot friction in the high-temperature flue gas and the like, is correspondingly less, so the tube top is not easy to generate the explosion.

As shown in figure 6, a reinforced coating with a thickness of about 0.05-0.08mm is prepared on the top of the tube of the heating surface of the pipeline on the surface of the induction welding layer, namely, on the part above 1/2 from the top of the tube to the root of the tube, by adopting a nickel-based nano ceramic composite brush plating method, the composite coating preparation process mainly comprises the steps of firstly completing the induction welding of the heating surface of the water-cooled wall, and then carrying out brush plating on the top of the tube, wherein the brush plating layer is thinner but has no inferior action to a thicker thermal spraying coating because the thermal expansion coefficients between the composite brush plating layer and the induction welding bottom layer are very close, the metallurgical bonding between the plating layer and the matrix can not fall off, the porosity is close to zero, effective close-fitting protection is formed on the bottom layer, after the tube top of the water-cooled wall is strengthened by double layers, the trouble of tube explosion can be completely avoided, and the effect of 1+1> 2' is achieved, in addition, the brush plating has simple equipment, The method has the advantages of less investment, flexible process, simple operation and the like, and the induction welding layer and the electric brush plating layer are protection schemes with high cost performance.

As shown in fig. 7, the brush plating technology is an important branch of electroplating technology, and is a process of obtaining a plating layer on the surface of a workpiece by an electrolytic method, the basic process of brush plating is to use a plating pen (anode) wrapped with a sheath and dipped with a special plating solution to be attached to a plated part of the workpiece (cathode) and make relative motion to form the plating layer, a brush plating power supply is connected between two stages in series, the plating pen consists of an anode and a plating pen holder, the plating pen holder comprises a conductive rod, a radiator, an insulating handle and the like, and in order to stably provide enough plated metal ions for a liquid layer on the surface of the workpiece, the high-concentration brush plating solution is directly pumped or naturally reflows between the cathode and the anode.

As shown in FIG. 8, the principle of preparing a composite coating on the surface of an induction fusion welding layer on the tube top of a water-cooled wall tube bank by brush plating is that the water-cooled wall tube bank is placed upright according to the flame spraying position, plating solution is poured from a gap between a plating pen and the tube top during brush plating, and is recycled after flowing into a bottom groove, and the arc length of the working surface of the plating pen is consistent with the arc length of the surface to be brush-plated on the tube top.

As shown in FIG. 9, in order to improve the brush plating efficiency and fully utilize the advantages of low cost, small size and light weight of the brush plating equipment, the invention provides a method of 'multiple parallel brushes and segmented plating', namely, two brushes are respectively arranged at two ends of each tube of a water wall tube bank, the water wall tube bank moves from two ends to the middle for brush plating, one water wall tube bank comprises six tubes, 12 brushes can work simultaneously (as shown by solid arrows in the figure), each brush plating machine finishes the brush plating length of 5m and the plating thickness of 0.05-0.08mm, the brush plating speed of 1-1.2 m/h is estimated to be about 4-5 h, the preparation work of cleaning surfaces is considered to be about 1-2 h, the brush plating of 10m tube bank is estimated to be about 5-7 h, and if the brush plating efficiency is further improved, two groups of brushes which work in opposite directions can be arranged at a position 2.5m away from two ends of the tube bank (as a dotted line in the figure) Arrows), that is, each brush plating machine only needs to finish for 2.5m, so that the total brush plating time is reduced to 3-4 hours.

Preparation of plating solution:

for the water wall tube bank heating surface bottom layer is the nickel-based self-fluxing alloy remelting layer, the nickel-based nano ceramic composite coating has high-temperature corrosion resistance, and the basic formula of the plating solution is shown in table 1:

TABLE 1 plating bath test formulation

In order to improve the high-temperature oxidation and corrosion resistance, a proper amount of ZrO is added into the nickel plating basic solution₂/Al₂O₃/NiCr-Cr₂C₃Nano ceramic powder to obtain nickel-base nano ceramic ZrO₂/Al₂O₃/NiCr-Cr₂C₃Brush plating of composite coating, ZrO₂/Al₂O₃/NiCr-Cr₂C₃The nanoparticles not only improve the high-temperature corrosion resistance, but also improve the corrosion resistance at high temperatureCan inhibit the growth of crystal grains of the coating, ZrO₂/Al₂O₃/NiCr-Cr₂C₃Adding the particles into the quick nickel brush plating solution according to the proportion of 10-15g/L, firstly magnetically stirring the prepared composite plating solution at constant temperature for 30min, then oscillating the composite plating solution for 30min by ultrasonic waves, and taking graphite as an anode and a water wall tube bank as a cathode in the brush plating.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (4)

1. A preparation method of a water-cooled wall heating surface induction fusion welding and brush plating composite coating is characterized by comprising the following steps of: comprises the following steps;

preparing a nickel-based self-fluxing alloy spraying powder material and a nickel-based nano ceramic composite plating solution;

step (2), carrying out sand blasting and coarsening treatment on the heating surface of the water wall tube bank by an automatic sand blasting machine;

step (3), preparing a nickel-based self-fluxing alloy coating with the thickness of 0.5 +/-0.1 mm by flame spraying on the surface of the tube bank;

step (4), performing high-frequency induction remelting on the spray coating;

step (5), strictly controlling the deformation of the tube bank by adopting a special tool in the induction remelting process;

step (6), performing brush plating on the tube top, wherein the thickness is 0.05-0.08 mm;

and (7) detecting the quality of the composite coating on the surface of the tube bank, and manually repairing the local defects.

2. The preparation method of the water-cooled wall heating surface induction fusion welding and brush plating composite coating according to claim 1, characterized by comprising the following steps: in the step (6), pretreatment before brush plating is required:

s21, brushing electric cleaning liquid, connecting an electrode positively, enabling the working voltage to be 8-10V, brushing and plating the pipe row surface to generate milky bubbles to achieve an oil removing effect, and washing with clear water;

s22, brush plating of an activating solution, connecting a negative electrode with a working voltage of 10-12V, activating until a plated part is black, generating carbon black and dirt on the surface, and washing with clear water.

3. The preparation method of the water-cooled wall heating surface induction fusion welding and brush plating composite coating according to claim 1, characterized by comprising the following steps: in the step (6), the brush plating method comprises the following specific steps:

s31, firstly plating a priming layer, namely firstly plating a layer of special nickel priming, wherein the special nickel has the function of improving the bonding strength of a plating layer and a base material, the brushing plating time is specifically based on the size of a workpiece, under general conditions, a light green plating layer appears on the surface of the workpiece, and the brushing plating voltage is 14-16V;

s32, plating a working layer, plating a nickel-based nano ceramic composite plating solution, positively connecting an electrode, and brushing the plating voltage to 12-15V.

4. The preparation method of the water-cooled wall heating surface induction fusion welding and brush plating composite coating according to claim 1, characterized by comprising the following steps: the preparation method of the nickel-based nano ceramic composite plating solution comprises the following steps:

adding proper amount of ZrO into nickel plating basic solution₂/Al₂O₃/NiCr-Cr₂C₃Nano ceramic powder to obtain nickel-base nano ceramic ZrO₂/Al₂O₃/NiCr-Cr₂C₃Brush plating of composite coating, ZrO₂/Al₂O₃/NiCr-Cr₂C₃The nano particles not only improve the high-temperature corrosion resistance, but also can inhibit the growth of coating crystal grains at high temperature to enable ZrO₂/Al₂O₃/NiCr-Cr₂C₃Adding the particles into the quick nickel brush plating solution according to the proportion of 10-15g/L, firstly magnetically stirring the prepared composite plating solution at constant temperature for 30min, then oscillating the composite plating solution for 30min by ultrasonic waves, and taking graphite as an anode and a water wall tube bank as a cathode in the brush plating.

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