CN115070421A

CN115070421A - Welding method of austenitic stainless steel and product thereof

Info

Publication number: CN115070421A
Application number: CN202210787886.3A
Authority: CN
Inventors: 王锐坤; 陈晓钿; 蔡伟龙; 郑羽佟
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2022-07-04
Filing date: 2022-07-04
Publication date: 2022-09-20

Abstract

The invention relates to the technical field of corrosion prevention of stainless steel appliances, in particular to a welding method of austenitic stainless steel and a product thereof, wherein the welding method comprises the step of welding the austenitic stainless steel by adopting pressure resistance welding, and the welding pressure is controlled to be less than 0.4MPa during the pressure resistance welding. The invention adopts resistance welding with adjustable welding pressure to weld austenitic stainless steel parts, thus realizing the purpose of controlling the transformation of original austenite phase to the induced martensite; in a specific resistance welding pressure deformation area, a structure which is dominated by austenite and has no martensite is obtained, the corrosion microcell is prevented from being formed in the area due to the coexistence of the austenite and the martensite, and the purpose of preventing the austenitic stainless steel from being rapidly corroded and rusted at present is achieved. The welding method is simple and convenient to operate, easy to popularize, free of replacing a large number of machining devices, and capable of saving production cost, and greatly improving working efficiency and economic benefits compared with a traditional welding method.

Description

Welding method of austenitic stainless steel and product thereof

Technical Field

The invention relates to the technical field of corrosion prevention of stainless steel appliances, in particular to a welding method of austenitic stainless steel and a product thereof.

Background

Stainless steel has excellent corrosion resistance, plasticity, compatibility, toughness and other characteristics, and thus is widely used in light/heavy industry and in the industry of articles for daily use. Among them, austenitic stainless steel has good processing property, corrosion resistance, welding property and mechanical property, and is widely applied to the fields of kitchenware, household appliances, decoration and the like.

Austenitic stainless steels generally have a structure of pure austenite at normal temperature, and some are austenite + a small amount of ferrite. The austenitic stainless steel has excellent welding performance, but compared with plain carbon steel, the austenitic stainless steel has the problems of intergranular corrosion, welding thermal crack, stress corrosion cracking, low-temperature catalysis of weld metal and the like more or less due to different welding method selections in the welding process due to special components and structures.

The pressure resistance welding is a method for welding by applying pressure to a weldment combined by electrodes and generating resistance heat by using current through a contact surface of a joint and an adjacent area, has the advantages of high production efficiency, good processing quality, low production cost, wide applicable welding materials, convenience in use and the like, and becomes an indispensable production process in the household electrical manufacturing industry because the welding is suitable for welding thin steel plates and the welding joint is high in quality.

In the welding process of austenitic stainless steel, strain-induced martensite phase transformation often exists in a resistance welding pressure deformation area, martensite and austenite form a corrosion micro-battery, and local micro-battery corrosion is easy to occur. The corrosion of the resistance welding pressure deformation area causes the surface quality of the product to be reduced, the appearance and the use effect of the product are influenced, and the normal service life of the product is shortened. On the other hand, austenitic stainless steel products represented by SUS304 are entering thousands of households, and the production amount, the use amount and the demand amount of various products using austenitic stainless steel are increasing, but at present, a reliable technology for preventing rapid corrosion of a welding stress deformation region of austenitic stainless steel has not appeared yet.

The problem of rapid corrosion of austenitic stainless steel is a pain point and a difficulty point existing in a plurality of enterprises at present, and the problem of corrosion and rusting after welding of austenitic stainless steel is solved, so that the method is very urgent for users and enterprises. Therefore, it is an important technical problem to be solved by those skilled in the art to develop a novel welding method for preventing corrosion and rust of austenitic stainless steel.

Disclosure of Invention

The first purpose of the invention is to provide a welding method of austenitic stainless steel, which realizes the purpose of controlling the transformation of original austenite phase to deformation induced martensite, and in a specific resistance welding pressure deformation area, a structure which is dominated by austenite and has no martensite is obtained, so that a corrosion micro-battery in the area is prevented from being formed due to the coexistence of austenite and martensite, local micro-battery corrosion is prevented, and the purpose of preventing the austenitic stainless steel from being rapidly corroded and rusted is achieved;

a second object of the invention is to provide an austenitic stainless steel product having excellent corrosion resistance.

The invention provides a welding method of austenitic stainless steel, which comprises the step of welding the austenitic stainless steel by adopting pressure resistance welding, wherein the welding pressure is controlled to be less than 0.4Mpa during the pressure resistance welding.

In the method, the austenitic stainless steel material with excellent surface quality is selected, the austenitic stainless steel parts are welded by resistance welding with adjustable welding pressure, and the welding pressure is controlled to be below 0.4Mpa in the whole welding process, so that the aim of controlling the transformation of the original austenite phase to the deformation induced martensite can be fulfilled, and the corrosion resistance of the austenitic stainless steel is improved.

Preferably, the technical scheme comprises the following steps:

s1, cutting a sample on the austenitic stainless steel plate, mechanically grinding and polishing the sample, and corroding the sample by using aqua regia to obtain the austenitic stainless steel plate to be processed;

s2, screening the austenitic stainless steel plate with a specific morphology to be processed, and preparing the austenitic stainless steel plate into corresponding parts according to a production process;

and S3, butting and positioning the parts to be welded, and welding by adopting pressure resistance welding.

Preferably, the technical scheme further comprises the step of sequentially polishing, cleaning and drying the pressure deformation area of the resistance welding after the welding is finished.

In the present embodiment, in step S1, the austenitic stainless steel sheet preferably has a thickness of 0.6mm, the size of the cut sample is (1-3) × (1-3) cm, and the position interval of the cut sample is greater than 100 mm.

The sample with a specific position and a specific size is cut, so that the uniformity and the integrity of the sample can be ensured in the sample preparation process, and the stress in the processing process is reduced.

In the present embodiment, it is preferable that the cutting is performed in an oil-free and pollution-free environment in step S1; after the aqua regia is corroded, cleaning the water by ultrasonic waves in absolute ethyl alcohol for 10-20min, and drying the water by blowing.

Preferably, in step S2, the specific morphology refers to that no pits or grain boundary ravines exist on the surface of the sample at the magnification of 500-.

This is because the surface features have many pits and grain boundary gullies, and the effects of deteriorating the corrosion performance of the steel sheet are amplified after subsequent forming, welding, leveling and polishing, so that the steel sheet with a specific surface feature needs to be selected.

Preferably, in step S3, in the pressure resistance welding, the welding pressure is controlled to be any value between 0.2Mpa and 0.4Mpa, and the welding speed is controlled to be any value between 120 and 180mm/min, and is preferably 150 mm/min.

Researches show that in the austenitic stainless steel processing process, the welding pressure and the welding speed are controlled, strain induced martensite phase transformation in an original austenite phase matrix can be effectively limited, the austenitic stainless steel without martensite in a welding stress deformation zone is finally obtained, and the corrosion resistance of SUS304 austenitic stainless steel is improved.

Preferably, in the technical scheme, the grinding is carried out for 20-40s by using a grinding wheel. The bulge caused by welding deformation is polished to be flat, and is dried after cleaning, so that good surface finish is kept, high residual stress in a welding structure is avoided, and meanwhile, the corrosion phenomenon of a local micro battery caused by tissue phase change is avoided.

Preferably, the austenitic stainless steel plate comprises any one or more of, but is not limited to, SUS304, SUS316 and SUS321, and meets the requirements of the latest national food-grade standard GB/T4806.9-2016.

The invention also discloses an austenitic stainless steel product prepared by using the welding method, and the austenitic stainless steel product also belongs to the protection scope of the invention.

The welding method of the austenitic stainless steel of the invention has at least the following technical effects:

1. the invention adopts resistance welding with adjustable welding pressure to weld austenitic stainless steel parts, thus realizing the purpose of controlling the transformation of original austenite phase to the induced martensite; in a specific resistance welding pressure deformation area, a structure which is dominated by austenite and has no martensite is obtained, the corrosion micro-battery in the area is prevented from being formed due to the coexistence of the austenite and the martensite, and the corrosion of the local micro-battery is prevented, so that the aim of preventing the austenitic stainless steel from being rapidly corroded and rusted is fulfilled;

2. according to the invention, the food-grade austenitic stainless steel with a specific surface appearance is preferably selected, so that the further influence of subsequent processing and daily use on the corrosion deterioration effect is reduced, the integral corrosion resistance of the austenitic stainless steel is improved, and the stability of mass production is improved;

3. the pressure resistance welding adopts specific welding pressure, and simultaneously, the specific welding speed is matched, the polishing and leveling of a welding area are carried out, and the like, so that the high residual stress in the welding structure is avoided, and the corrosion phenomenon of a local micro battery caused by the phase change of the structure is avoided;

4. the welding method is simple and convenient to operate, easy to popularize, free of the need of replacing a large number of processing devices, and capable of saving production cost, greatly improving working efficiency and economic benefits compared with the welding method in the prior art, filling the gap of dealing with the problem of rapid corrosion and rusting of austenitic stainless steel appliances, and having important guiding significance and use value for enterprise production and related research.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic view of an electric kettle;

FIG. 2 is the surface morphology of the original plate of example 1 on a scanning electron microscope;

FIG. 3 is the surface morphology of the original plate of comparative example 1 on a scanning electron microscope;

FIG. 4 is a comparison of corrosion (a) and no corrosion (b) in the welding heat affected zone of the spout of the electric kettle;

FIG. 5 is a graph of the saturation magnetization of the original plate material in example 1;

FIG. 6 is a saturation magnetization curve at a weld in example 1;

FIG. 7 is a saturation magnetization curve at the weld of comparative example 2;

FIG. 8 is a saturation magnetization curve at the weld of comparative example 4;

FIG. 9 is an XRD phase analysis of the weld of example 1;

FIG. 10 is XRD phase analysis at the weld of comparative example 4.

Reference numerals:

1: a kettle body of the electric kettle; 2: a spout of the electric kettle; 3: the kettle body and the kettle mouth are connected with a welding seam.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise, and further, it is understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, devices, components, and/or combinations thereof.

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. 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.

As shown in fig. 1-10, the embodiment of the invention takes the welding of the spout of the electric kettle as an example, and researches on the welding method of the invention.

The food grade austenitic stainless steel selected for use in the embodiment of the present invention is SUS304 steel, and the chemical composition thereof is shown in table 1.

TABLE 1 SUS304 Steel each component content

Example 1

S11, cutting two samples on a food-grade SUS304 austenitic stainless steel plate, wherein the cutting positions are in the middle of the stainless steel plate, the left and right are symmetrical about a central line, the distance is 150mm, the area size of the samples is 2x2cm, the samples are cut and sampled in an environment without oil and chemical reagent pollution, and after mechanical grinding and polishing, the samples are corroded by aqua regia, and are cleaned and dried by absolute ethyl alcohol;

s12, placing the sample in an electron scanning microscope for observation, wherein the magnification is 500 times, and the surface appearance is shown in figure 2;

according to the image result, the surface appearance of the steel plate has no obvious pits and grain boundary gullies;

s13, cutting the stainless steel plate into the required sizes of all parts, removing burrs, preparing different parts such as a kettle body and a kettle mouth according to a production process, and then cleaning;

s14, butt-jointing and positioning the kettle body 1 and the kettle mouth 2, and welding the kettle mouth and the kettle body by adopting pressure resistance welding with the welding pressure of 0.2Mpa and the welding speed of 150 mm/min;

and S15, polishing the welding pressure deformation area to be flat, and then cleaning and drying.

Example 2

S21, cutting two samples on a food-grade SUS304 austenitic stainless steel plate, wherein the cutting positions are in the middle of the stainless steel plate, the left and right are symmetrical about a central line, the distance is 150mm, the area size of the samples is 2x2cm, the samples are cut and sampled in an environment without oil and chemical reagent pollution, and after mechanical grinding and polishing, the samples are corroded by aqua regia, and are cleaned and dried by absolute ethyl alcohol;

s22, observing the sample in an electron scanning microscope with the magnification of 500 times, wherein the surface appearance is shown in figure 2;

s23, cutting the stainless steel plate into the required sizes of all parts, removing burrs, preparing different parts such as a kettle body and a kettle mouth according to a production process, and then cleaning;

s24, butt-jointing and positioning the kettle body 1 and the kettle mouth 2, and welding the kettle mouth and the kettle body by adopting pressure resistance welding with the welding pressure of 0.4Mpa and the welding speed of 150 mm/min;

and S25, polishing the welding pressure deformation area to be flat, and then cleaning and drying.

Comparative example 1

SD1, cutting two samples on food-grade SUS304 austenitic stainless steel plates of other batches, wherein the cutting positions are symmetrical about the center line at the left and right, the distance is 150mm, the area size of the samples is 2x2cm, cutting and sampling are carried out in an environment without oil or chemical reagent pollution, and after mechanical grinding and polishing, the samples are corroded by aqua regia and are cleaned by absolute ethyl alcohol and dried;

SD2, the sample was observed in an electron scanning microscope at a magnification of 500, and the surface topography is shown in FIG. 3.

According to image results, the surface appearance of the steel plate has obvious pits and grain boundary gullies.

Comparative example 2

The following differences from example 1 exist:

the kettle body 1 and the kettle mouth 2 are butted and positioned, pressure resistance welding is adopted, the welding pressure is 0.6Mpa, the welding speed is 150mm/min, and the kettle mouth and the kettle body are welded.

Comparative example 3

The difference from example 1 is that:

butt-jointing and positioning the kettle body 1 and the kettle mouth 2, and welding the kettle mouth and the kettle body by adopting pressure resistance welding with the welding pressure of 0.8Mpa and the welding speed of 150 mm/min.

Comparative example 4

The difference from example 1 is that:

the kettle body 1 and the kettle mouth 2 are butted and positioned, and the kettle mouth and the kettle body are welded by adopting one-step forming laser welding without welding pressure at the welding speed of 150 mm/min.

In order to investigate the corrosion resistance of the electric kettles manufactured in the examples, corrosion resistance tests were conducted on examples 1 to 2 and comparative examples 1 to 4.

The test method comprises the following steps: and adding a 5% citric acid solution into the electric kettle, soaking for 5min, observing whether the welding pressure affected area is corroded, and obtaining a test result shown in table 2.

TABLE 2 Corrosion resistance test results

As can be seen from comparing fig. 2 and 3, when there are many pits and grain boundary ravines on the surface of the austenitic stainless steel sheet to be processed, the effect of deteriorating the corrosion performance is amplified after subsequent forming, welding, leveling and polishing, and therefore, a steel sheet with a specific surface morphology needs to be selected when processing the austenitic stainless steel product.

In order to further represent the influence of welding on the magnetism strength of an austenite sample, the magnetization strengths of a welding seam of a kettle nozzle and an original plate are measured by a VSM vibration sample magnetometer (a PPMS physical property testing system), the saturation magnetization strength is obtained by intersecting a tangent line of a saturation magnetization curve and a vertical coordinate, and the magnetism strength of a sample is represented.

As can be seen from fig. 5 to 8, the magnetic properties of the austenitic stainless steel welded joints obtained by the electric resistance welding at 0.2Mpa (example 1) and the electric resistance welding at 0.6Mpa (comparative example 2) were changed from those of the original plate materials and were significantly increased, whereas the magnetic properties of the test pieces obtained by the laser welding at the primary molding without the welding pressure were not significantly changed.

Since the modification of the magnetic strength of the samples of the pressure resistance welding may be related to the martensitic transformation at the welding seam, the XRD phase analysis of the welding seam was performed by selecting the samples of example 1 and comparative example 4, and the results are shown in 9-10.

The result shows that no matter one-step forming laser welding or pressure resistance welding is adopted, the welding seam has martensite phase transformation in the welding process, and martensite exists.

And combining the corrosion resistance test result, in the welding process, the austenitic stainless steel welding seam generates martensite phase transformation no matter pressure resistance welding or one-step forming laser welding is adopted due to the influence of welding pressure and welding heat. When the pressure resistance welding adopts the welding pressure of 0.2Mpa for welding, the probability of inhibiting the martensite phase transformation can basically reach the method of one-step forming laser welding, and compared with the method of one-step forming laser welding, the pressure resistance welding has the advantages of low processing cost, easy popularization, no need of replacing a large amount of processing equipment, production cost saving and capability of greatly improving the working efficiency and the economic benefit.

As can be seen from table 1 and fig. 9 to 10, in the samples of examples 1 and 2 in which the welding pressure was less than 0.4Mpa, martensite was present in the weld (wall surface) during the welding process, although martensite was generated. In the 5% citric acid solution soaking test, the welding stress affected zone (in the wall) has no corrosion, which shows that in the zone, the original austenite phase-shape-transformation induced martensite transformation is controlled, and no martensite exists in the zone. Therefore, the rapid corrosion and rust of the austenitic stainless steel can be effectively prevented by adopting the pressure resistance welding with the welding pressure less than 0.4Mpa, and the corrosion resistance of the austenitic stainless steel is improved.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. The welding method of the austenitic stainless steel is characterized by comprising the step of welding the austenitic stainless steel by adopting pressure resistance welding, wherein the welding pressure is controlled to be less than 0.4Mpa during the pressure resistance welding.

2. The method of welding austenitic stainless steel of claim 1, comprising the steps of:

s2, screening the austenitic stainless steel plate with the specific morphology to be processed, and preparing the austenitic stainless steel plate into corresponding parts according to the production process;

3. The method of welding austenitic stainless steels according to claim 2, further comprising, after welding, sequentially grinding, cleaning and blow-drying the resistance welding pressure deformation zone.

4. The method of welding austenitic stainless steels according to claim 2, wherein the thickness of the austenitic stainless steel sheet is 0.6mm, the size of the cut sample is (1-3) × (1-3) cm, and the position interval of the cut sample is more than 100mm in step S1.

5. The method for welding austenitic stainless steel according to claim 2, wherein the cutting is performed in an oil-free and pollution-free environment in step S1; after the aqua regia is corroded, cleaning the water by ultrasonic waves in absolute ethyl alcohol for 10-20min, and drying the water by blowing.

6. The method for welding austenitic stainless steel as claimed in claim 2, wherein in step S2, the specific morphology indicates that no pits or grain boundary ravines exist on the surface of the sample at magnification of 500-.

7. The method for welding austenitic stainless steel as claimed in claim 2, wherein in step S3, the welding pressure is controlled to be 0.2-0.4Mpa, and the welding speed is controlled to be 120-180mm/min during the pressure resistance welding.

8. The method for welding austenitic stainless steels according to claim 3, wherein the grinding is performed for 20-40 seconds by using a grinding wheel.

9. The method of welding the austenitic stainless steel of claim 2, wherein the austenitic stainless steel plate comprises, but is not limited to, any one or more of SUS304, SUS316, and SUS 321.

10. A product of austenitic stainless steel, characterized in that it is produced by a welding method according to any of claims 1-9.