Method for remelting in atmosphere furnace with anti-corrosion coating on heating surface of boiler membrane wall

Abstract

The invention belongs to the technical field of membrane wall coating remelting, and discloses a method for remelting in an atmosphere furnace with an anti-corrosion coating on the heating surface ofthe boiler membrane wall. The method includes the steps that an automatic sandblasting machine is used for conducting sandblasting roughening treatment on the surfaces of pipe rows, and flame-sprayednickel-based self-fluxing alloy powder is adopted to prepare a coating; a remelting system is formulated for coating materials and the coating thickness, and heating, heat preservation and cooling curves are designed; high-temperature alloy steel is used for being made into a row frame vehicle with an idler wheel, the pipe rows are hung and placed on the row frame vehicle by a truss, finally the row frame vehicle is pushed into the furnace along a track, and a furnace door is closed; the atmosphere furnace is started, and inert protective gas is introduced and heated; the remelting temperatureis controlled; after remelting of the pipe rows, the row frame vehicle is pulled out of the furnace; and the remelting effect of the coating on the surfaces of the pipe rows is tested. According to the method, the temperature in the furnace is uniform and accurately adjustable, the main disadvantages of high-frequency induction remelting are completely overcome, the coating preparation quality can be significantly improved, the high-temperature anti-corrosion performance of the boiler water wall is effectively improved, and the service life of the boiler water wall is prolonged.

Description

technical field [0001] The invention belongs to the technical field of coating remelting of membrane-type water-cooled walls, and in particular relates to a remelting method in an atmosphere furnace of an anti-corrosion coating on a heating surface of a membrane-type water-cooled wall of a boiler. Background technique [0002] Currently, the closest prior art: [0003] With the accelerated implementation of the country's new energy development strategy, the domestic waste incineration power generation industry has developed rapidly in recent years. At present, the bottleneck problem that restricts the technical development of waste incineration power generation is that the membrane water wall of the boiler is severely corroded due to high temperature, and tube bursts occur frequently. In recent years, the International Center for Cancer Research has listed dioxin as a first-class human carcinogen. In order to prevent the secondary pollution of dioxin at low temperature duri...

AI Technical Summary

Problems solved by technology

[0005] (1) Since the heating surface of the water-cooled wall tube row is an irregular curved surface welded by the tube and the fin, when heating with a high-frequency coil, there are errors in the thickness of the coating, the width of the fin, the size of the weld, etc., resulting in The distance between the coil and the surface of the coating is difficult to be consistent, and the difference in height can reach 3cm, so that the depth of the coating being heated is different. Far parts such as fins have not yet started to melt, so the unevenness of coating remelting is more serious

Even if it is made into a profiling coil, the superposition of profiling manufacturing error and tube row structure error will make the gap size different, and the effect is still unsatisfactory

[0006] (2) Since the pipe row is naturally cooled in the air after remelting and heating, the faster cooling rate causes the residual tensile stress in the coating to be larger, thus laying the root of the cracks;

[0007] (3) Thousands of degrees of high temperature for coating remelting cause serious oxidation inside and on the back of the tube

The oxide skin in the pipe is very harmful, because there is a difference in the thermal expansion system of the pipe matrix and the oxide skin, so the oxide skin is easy to fall off under the cyclical pull of the base body's thermal expansion and contraction, and is washed to the elbow by high-pressure steam to deposit and accumulate. After reaching a certain level, the local temperature rise will intensify, resulting in the risk of tube explosion;

[0008] (4) The heating temperature of the high-frequency induction coil is difficult to precisely control, which undoubtedly makes the uneven heating of the coating and the plight of oxide skin growth worse;

[0009] (5) For the tube row several meters long, high-frequency induction remelting belongs to local heating, and with the feeding movement of the tube row in the coil, the local high temperature causes serious bending deformation of the tube row, and special tooling must be used Perform deformation correction

[0012] (1) The high-grade stainless steel thickened pipes used in the prior art are expensive; the ordinary stainless steel used has a limited service life at high temperatures; when the 625 alloy is used, the temperature will reach 550 ° C and sensitization will occur, and the corrosion resistance of the material will decline rapidly. Once the service temperature exceeds 700°C, its actual service life is only 50% of the design life, generally no more than three years

[0013] (2) The distance between the coil and the surface of the coating in the high-frequency induction remelting method is difficult to be consistent, so that the coating is heated to a different depth; Different sizes, the effect is still not ideal

The top of the tube close to the coil is melted first, and when the root of the tube that is melted after waiting is also melted, the coating on the top of the tube has melted and flowed, resulting in uneven remelting quality of each part

[0014] (3) Since the pipe row is naturally cooled in the air after remelting and heating, the faster cooling rate results in greater residual tensile stress in the coating, which is prone to cracks

[0015] (4) The heating temperature of the high-frequency induction coil is difficult to precisely control, which will aggravate the uneven heating of the coating and the problem of scale growth

[0016] (5) High-frequency induction remelting belongs to local heating, and the local high temperature causes serious bending deformation of the pipe row, and special tooling must be used for deformation correction

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