CN109628933B - Stainless steel metallographic corrosive agent and application method thereof - Google Patents
Stainless steel metallographic corrosive agent and application method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
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Abstract
The invention relates to the technical field of metallographic corrosion of stainless steel materials, in particular to a metallographic corrosive agent for stainless steel and an application method thereof. The metallographic corrosive agent comprises the following components in percentage by volume: 12-25% of concentrated nitric acid solution; 47-70% of absolute ethyl alcohol solution; 16-30% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 40-58%. The phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be quickly and obviously shown through the mutual synergistic action of different solutions. Compare with current rare aqua regia or iron chloride corrosive, the corrosive process of this application is steady slow, can not cause the over-corrosion to the grain boundary of powder metallurgy stainless steel when corroding out the phase boundary of deformation stainless steel, provides very big facility for follow-up detection to the welding quality.
Description
Technical Field
The invention relates to the technical field of metallographic corrosion of stainless steel materials, in particular to a metallographic corrosive agent for stainless steel and an application method thereof.
Background
The ordinary wrought stainless steel is a stainless steel processed by rolling (hot rolling, cold rolling), pressing, etc., and has high strength, good toughness, excellent corrosion resistance and weldability, and is widely used in the industry. Powder metallurgy stainless steel is stainless steel manufactured by a powder metallurgy method (injection molding). The two stainless steels have the same grade, but different properties due to different manufacturing processes.
The stainless steel laser welding process has the advantages of high strength after welding, small heat affected zone, attractive welding spot, high efficiency, easiness in automation and the like, and is rapidly developed in the manufacturing industry, particularly in the field of precision devices. The powder metallurgy stainless steel is more popular because the process difficulty and the cost in the aspect of manufacturing complex and precise small components are lower. It is becoming more and more common to use laser welding to achieve an effective connection between common wrought stainless steels and powder metallurgy stainless steels.
After the deformed stainless steel and the powder metallurgy stainless steel are welded by laser welding, a heterogeneous stainless steel welding seam is formed at the welding position. The quality of the laser welding is judged by observing the metallographic structure of the cross section of the welding spot or the welding wire, and the method is an indispensable, effective and scientific means. However, deformed stainless steels exhibit different degrees and rates of corrosion from conventional single dilute aqua regia or ferric chloride etchants due to differences in the properties of the deformed stainless steel and the powder metallurgy stainless steel.
As shown in FIG. 1, in general, when the phase boundary of the ordinary deformed stainless steel 1 is corroded, the surface of the powder metallurgy stainless steel 2 is corroded, namely, the cross section 3 of the welding spot corroded by a single corrosive agent cannot achieve the ideal corrosion effect.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a stainless steel metallographic corrosive agent aiming at the defects in the prior art, and overcome the defect that the surface of powder metallurgy stainless steel is over-corroded when the deformed stainless steel phase boundary is corroded by the conventional corrosive agent.
The technical scheme adopted by the invention for solving the technical problem is to provide a stainless steel metallographic corrosive agent which comprises the following components in percentage by volume: 12-25% of concentrated nitric acid solution; 47-70% of absolute ethyl alcohol solution; 16-30% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 40-58%.
According to a further preferred embodiment of the present invention, the composition comprises the following components by volume ratio: 16-21% of concentrated nitric acid solution; 50-67% of absolute ethyl alcohol solution; 18-28% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 48-50%.
In a further preferred embodiment of the present invention, a method for preparing a corrosive agent for a stainless steel metallographic phase is provided, which comprises the following steps: adding the concentrated nitric acid solution into an absolute ethyl alcohol solution to obtain a nitric acid-ethyl alcohol solution; and adding the ferric chloride solution into the nitric acid alcohol solution to obtain the metallographic corrosive.
In a further preferable embodiment of the present invention, in the nital solution, the volume fraction of the concentrated nitric acid solution is 21 to 25%, and the volume fraction of the absolute ethyl alcohol solution is 75 to 79%.
The invention further preferably provides an application method of the stainless steel metallographic corrosive agent, which is used for corroding a phase boundary of the common deformed stainless steel and a grain boundary of the powder metallurgy stainless steel on the cross section of the welding spot.
According to a further preferable scheme of the invention, a metallographic corrosive agent is adopted to wipe and corrode the cross section of the welding spot until a phase boundary of the deformed stainless steel and a grain boundary of the powder metallurgy stainless steel are clearly visible.
Further preferred embodiments of the present invention are: the wiping corrosion time is 2-10 s.
Further preferred embodiments of the present invention are: and before wiping corrosion, performing coarse grinding, fine grinding and polishing on the cross section of the welding point.
Further preferred embodiments of the present invention are: and after wiping corrosion, washing and drying the cross section of the welding spot.
The invention has the beneficial effects that the stainless steel metallographic corrosive provided by the invention can corrode the cross section of a welding spot, and the phase boundary of the deformed stainless steel and the crystal boundary of the powder metallurgy stainless steel can be quickly and obviously shown through the mutual synergistic action of different solutions. Compare with current rare aqua regia or iron chloride corrosive, the corrosive process of this application is steady slow, can not cause the over-corrosion to the grain boundary of powder metallurgy stainless steel when corroding out the phase boundary of deformation stainless steel, provides very big facility for follow-up detection to the welding quality.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a microstructure of a cross-section of a weld joint of an embodiment of the present invention after erosion;
FIG. 2 is a microstructure of a cross-section of a weld joint of an embodiment of the invention without over-corrosion.
Detailed Description
The invention provides a stainless steel metallographic corrosive agent and an application method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and more clear. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Deformed stainless steel and powder metallurgy stainless steel in the present invention mainly refer to SUS301, SUS304, SUS316 and other commonly used stainless steels having similar or analogous characteristics. The chemical agents used, unless otherwise specified, are commercially available in a conventional manner.
The embodiment of the invention provides a stainless steel metallographic corrosive agent, which comprises the following components in percentage by volume:
12-25% of concentrated nitric acid solution;
47-70% of absolute ethyl alcohol solution;
16-30% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 40-58%.
The invention provides a stainless steel metallographic corrosive agent for corroding the cross section of a welding spot, and can simultaneously corrode a phase boundary of deformed stainless steel and a crystal boundary of powder metallurgy stainless steel. Compared with the existing dilute aqua regia or ferric chloride corrosive, the corrosive disclosed by the invention is stable and slow in corrosion process, cannot cause over-corrosion to the grain boundary of the powder metallurgy stainless steel when corroding the phase boundary of the deformed stainless steel, and provides great convenience for the subsequent detection of welding quality.
Preferably, the stainless steel metallographic corrosive agent comprises, by volume ratio,
16-21% of concentrated nitric acid solution;
50-67% of absolute ethyl alcohol solution;
18-28% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 48-50%. By adopting the optimized proportion, the effect of corroding the cross section of the welding spot is more visual and clear.
Further, an embodiment of the present invention further provides a preparation method of the above stainless steel metallographic corrosive agent, which is characterized by specifically including the following steps:
the method comprises the steps of adding a concentrated nitric acid solution into an anhydrous ethanol solution to obtain a nitric acid-ethanol solution;
slowly adding the concentrated nitric acid solution into the absolute ethyl alcohol solution from small to large at room temperature, dipping the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution by using a cotton swab to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel can just slightly display part of a grain boundary of the powder metallurgy stainless steel, so that the preparation of the nitric acid alcohol solution is completed.
And adding the ferric chloride solution into the nitric acid alcoholic solution to obtain the metallographic corrosive.
Slowly adding the ferric chloride solution into the prepared nitric acid alcohol solution in the step (1) from a small amount to a large amount, and meanwhile, dipping a cotton swab in a mixed solution of the nitric acid alcohol solution and the ferric chloride solution to wipe the cross section of the welding spot until a phase boundary on the deformed stainless steel and a crystal boundary of the powder metallurgy stainless steel material can be quickly and clearly displayed, so that the preparation of the metallographic corrosive agent for the welding spot of the common deformed stainless steel and the powder metallurgy stainless steel is finished.
Preferably, in the alcohol nitrate solution in the first step, the volume fraction of the concentrated nitric acid solution is 21-25%, and the volume fraction of the anhydrous ethanol solution is 75-79%.
Still further, the embodiment also provides an application method of the stainless steel metallographic corrosive agent, which is applied to a phase boundary of common deformed stainless steel and a grain boundary of powder metallurgy stainless steel corroded on the cross section of the welding spot, and specifically comprises the following steps:
a. performing coarse grinding, fine grinding and polishing on the cross section of the welding spot;
the method comprises the steps of firstly adopting large sand paper to roughly grind the cross section of a welding spot, then adopting small sand paper to finely grind the cross section of the welding spot, then using polishing cloth and matching with a proper amount of polishing agent to throw scratches on the cross section of the welding spot, wherein the scratches cannot be obvious scratches, so that the phase boundary of deformed stainless steel and the crystal boundary of powder metallurgy stainless steel can be better presented, and using dust-free cloth or a cotton swab to clean liquid and dirt on the cross section of the welding spot. The smoother the corrosion surface, the better the corrosion effect.
b. Wiping the cross section of the corroded welding spot by adopting a metallographic corrosive agent;
a small amount of prepared metallographic corrosive agent is dipped by a cotton swab, and the cross section of the welding point is wiped and corroded, so that the over-corrosion of the whole welding point is avoided, and the dirty deposition on the cross section of the welding point is reduced.
And determining the corrosion degree according to the corrosion time. The shorter the action time of the corrosive agent is, the lighter the cross section of the welding spot is corroded; the longer the action time, the more heavily the cross-section of the weld spot corrodes. Preferably, the wiping corrosion time of the embodiment is 2-10 s.
c. And (5) washing and drying the cross section of the welding spot.
Referring to fig. 2, when the phase boundary 4 on the deformed stainless steel 1 side and the grain boundary 5 on the powder metallurgy stainless steel 2 side on the cross section 3 of the to-be-welded point can be distinguished obviously, the corrosive agent residual liquid on the cross section 3 of the to-be-welded point is washed clean by clear water, and meanwhile, the surface of the corrosive agent residual liquid is wiped clean and dried by a cotton swab, so that preparation is made for subsequent metallographic observation and related measurement.
The invention is illustrated in detail below with specific examples:
example one
Slowly adding a 65% concentrated nitric acid solution into a 99.75% absolute ethyl alcohol solution from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of grain boundaries of the powder metallurgy stainless steel, so as to finish the preparation of the nitric acid alcohol solution. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 14.6 percent, and the volume fraction of the absolute ethyl alcohol solution is 85.4 percent.
And (3) slowly adding 40% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab into a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of the concentrated nitric acid solution is 12%, the volume fraction of the absolute ethyl alcohol solution is 70%, and the volume fraction of the ferric chloride solution is 18%. When the cross section of the welding spot is etched by using the etchant in the first embodiment, the wiping etching time is preferably 10 s.
Example two
Slowly adding a concentrated nitric acid solution with the concentration of 68% into an absolute ethyl alcohol solution with the concentration of 99.8% from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of grain boundaries of the powder metallurgy stainless steel, so that the preparation of the nitric acid alcohol solution is completed. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 33.3 percent, and the volume fraction of the absolute ethyl alcohol solution is 66.7 percent.
And (3) slowly adding 58% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab into a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of a concentrated nitric acid solution is 25%, the volume fraction of an absolute ethyl alcohol solution is 50%, and the volume fraction of a ferric chloride solution is 25%. When the etchant of the second embodiment is used to etch the cross section of the solder joint, the wiping etching time is preferably 2 s.
EXAMPLE III
Slowly adding a 65% concentrated nitric acid solution into a 99.8% absolute ethyl alcohol solution from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of a grain boundary of the powder metallurgy stainless steel, so as to finish the preparation of the nitric acid alcohol solution. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 21 percent, and the volume fraction of the absolute ethyl alcohol solution is 79 percent.
And (3) slowly adding 49% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab in a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of the concentrated nitric acid solution is 14.7%, the volume fraction of the absolute ethyl alcohol solution is 55.3%, and the volume fraction of the ferric chloride solution is 30%. When the etchant of the third embodiment is used to etch the cross section of the solder joint, the wiping etching time is preferably 8 s.
Example four
Slowly adding a concentrated nitric acid solution with the concentration of 68% into an absolute ethyl alcohol solution with the concentration of 99.75% from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of grain boundaries of the powder metallurgy stainless steel, so that the preparation of the nitric acid alcohol solution is completed. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 25 percent, and the volume fraction of the absolute ethyl alcohol solution is 75 percent.
And (2) slowly adding 50% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab into a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of a concentrated nitric acid solution is 21%, the volume fraction of an absolute ethyl alcohol solution is 63%, and the volume fraction of a ferric chloride solution is 16%. When the cross section of the solder joint is etched using the etchant in the fourth embodiment, the wipe etching time is preferably 3.5 s.
EXAMPLE five
Slowly adding a concentrated nitric acid solution with the concentration of 66.9% into an absolute ethyl alcohol solution with the concentration of 99.85% from small to large, dipping a cotton swab in the nitric acid solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel can slightly display part of grain boundaries to finish the preparation of the nitric acid solution. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 22 percent, and the volume fraction of the absolute ethyl alcohol solution is 78 percent.
And (3) slowly adding 48% of ferric chloride solution into the nitric acid-alcohol solution from small to large, dipping a cotton swab in the mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of the welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, and thus, the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of a concentrated nitric acid solution is 16%, the volume fraction of an absolute ethyl alcohol solution is 56%, and the volume fraction of a ferric chloride solution is 28%. When the etchant in the fifth embodiment is used to etch the cross section of the solder joint, the wiping etching time is preferably 7 s.
EXAMPLE six
Slowly adding a concentrated nitric acid solution with the concentration of 65.7% into an absolute ethyl alcohol solution with the concentration of 99.72% from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel can slightly display part of grain boundaries to finish the preparation of the nitric acid alcohol solution. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 25 percent, and the volume fraction of the absolute ethyl alcohol solution is 75 percent.
And (3) slowly adding 49.3% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab into the mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the crystal boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive is prepared. In the metallographic corrosive, the volume fraction of the concentrated nitric acid solution is 20.5%, the volume fraction of the absolute ethyl alcohol solution is 61.5%, and the volume fraction of the ferric chloride solution is 18%. When the cross section of the welding spot is etched by using the etchant in the sixth embodiment, the wiping etching time is preferably 4 s.
EXAMPLE seven
Slowly adding a concentrated nitric acid solution with the concentration of 66% into an absolute ethyl alcohol solution with the concentration of 99.8% from small to large, dipping a cotton swab in the nitric acid alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of grain boundaries, so as to finish the preparation of the nitric acid alcohol solution. Wherein, the volume fraction of the concentrated nitric acid solution in the nital solution is 24.6 percent, and the volume fraction of the absolute ethyl alcohol solution is 75.4 percent.
And (3) slowly adding 49% by mass of ferric chloride solution into the nitric acid-alcohol solution from a small amount to a large amount, and meanwhile, dipping a cotton swab in a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until the phase boundary of the deformed stainless steel and the grain boundary of the powder metallurgy stainless steel can be rapidly and clearly displayed, so that the stainless steel metallographic corrosive agent is prepared. In the metallographic corrosive, the volume fraction of a concentrated nitric acid solution is 19%, the volume fraction of an absolute ethyl alcohol solution is 58% and the volume fraction of a ferric chloride solution is 23%. When the cross section of the solder joint is etched using the etchant in the seventh embodiment, the wipe etching time is preferably 6 s.
It should be understood that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some technical features; and all such modifications and alterations are intended to fall within the scope of the appended claims.
Claims (6)
1. The preparation method of the stainless steel metallographic corrosive agent is characterized by comprising the following steps of:
the method comprises the following steps: slowly adding a concentrated nitric acid solution into an absolute ethyl alcohol solution from small to large, dipping a cotton swab in a nitric acid-alcohol solution combined by the concentrated nitric acid solution and the absolute ethyl alcohol solution to wipe the cross section of a welding spot, and stopping adding the concentrated nitric acid solution when the surface of the powder metallurgy stainless steel just can slightly display part of a grain boundary of the powder metallurgy stainless steel to obtain the nitric acid-alcohol solution;
step two: slowly adding ferric chloride solution into the nitric acid-alcohol solution from small amount to large amount, and meanwhile, dipping a cotton swab into a mixed solution of the nitric acid-alcohol solution and the ferric chloride solution to wipe the cross section of a welding spot until a phase boundary on the deformed stainless steel and a crystal boundary of the powder metallurgy stainless steel material can be rapidly and clearly displayed, so as to obtain a metallographic corrosive agent;
the stainless steel metallographic corrosive agent comprises the following components in percentage by volume: 12-25% of concentrated nitric acid solution; 47-70% of absolute ethyl alcohol solution; 16-30% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 40-58%.
2. The preparation method of claim 1, wherein the stainless steel metallographic corrosive agent comprises the following components in percentage by volume: 16-21% of concentrated nitric acid solution; 50-67% of absolute ethyl alcohol solution; 18-28% of ferric chloride solution, wherein the mass fraction of ferric chloride in the ferric chloride solution is 48-50%, and the sum of the contents of all the components is one hundred percent.
3. The method according to claim 2, wherein the volume fraction of the concentrated nitric acid solution is 21 to 25% and the volume fraction of the absolute ethanol solution is 75 to 79% in the nital solution.
4. The method according to claim 3, wherein the wiping corrosion time in the second step is 2 to 10 seconds.
5. The method of claim 4, further comprising the steps of:
and before the first step, performing coarse grinding, fine grinding and polishing on the cross section of the welding point.
6. The method of claim 5, further comprising the steps of:
and after the second step, washing and drying the cross section of the welding spot.
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