Automatic machine for revealing metal microstructures

Description

/ 8 AUTOMATIC MACHINE FOR REVEALING METAL MICROSTRUCTURES Field of invention

[001] Sample preparation for metallographic testing. Fundamentals of the invention

[002] The practice of preparing samples for metallography requires that the microstructure be revealed by means of chemical reactions of acids with the metal for its clear characterization and visualization under metallographic microscopes.

[003] Currently, in all metallographic laboratories around the world, the chemical reagent is applied manually using wash bottle type sprayers.

[004] The practice requires handling chemicals, involving manual work in which bottles of acids, alcohols, and neutralizers are poured from one container to another, in addition to care with projections and disposal of waste, as well as the release of gases, which requires the activity to be carried out in receptacles known as "fume hoods," where the generated gases are aspirated and filtered before atmospheric emission.

[005] This activity in a metallographic laboratory has the highest history of accidents resulting in material and personal damage in laboratories. For this activity, the use of personal and collective protective equipment (PPEs and CPEs) is recommended.

[006] One of the most important features of this invention is that it automates a dangerous manual task that has never been brought to market, bringing safety and practicality to professionals in metallographic laboratories.

[007] In a query to the ChatGPT artificial intelligence (AI) conducted in February 2025, requesting an estimate of how many metallographic laboratories exist in the world, the AI ​​returned the following report: Petition 870250071134, dated 12 / 08 / 2025, page 4 / 22 / 8

[008] Sectors that use metallography laboratories • Automotive industry • Aerospace • Metallurgy and steelmaking • Manufacturing industry • Research and universities • Oil and gas • Defense and military

[009] Estimate based on industrial companies: • The world has approximately 500,000 institutions, and 10% of these industries have in-house metallography laboratories, totaling 50,000 laboratories.

[010] Independent and academic laboratories • Universities and research centers worldwide: approximately 10,000 • Independent testing laboratories: estimated at 5,000.

[011] Conclusion, in summary: • 50,000 industrial laboratories • 10,000 academic laboratories • 5,000 independent laboratories

[012] Approximate total: 65,000 metallography laboratories in the world.

[013] An important technical problem solved by this invention is the rigorous standardization of the times during which the reagent acts on the sample. It is very common for laboratory technicians to apply the reagent without using a stopwatch, controlling the time only by their feeling and experience in the task. In addition, any human distraction can cause acid or alcohol to be projected into the vicinity of the activity, causing some type of accident such as burns or fire. With this invention, the amount of handling of chemical products will be reduced, preventing breakage of glassware and spills of chemical products in the laboratory, which are the main causes of accidents in laboratories.

[014] We know that each type of chemical reagent and type of material to be analyzed under a microscope requires different reaction times. For example, the 3% Nital reagent (a solution of nitric acid in ethyl alcohol) requires 15 seconds for revealing the microstructure of low-carbon steels, and 5 seconds for high-carbon steels. Any failure to control the time can result in a microstructural revelation that provides false or low-quality information. If Petition 870250071134, dated 12 / 08 / 2025, page 5 / 22 / 8 if this occurs, the decision-making process for the application of a particular metal part may result in a failure that can cause accidents of various proportions, for example: in the use of vehicle suspensions, bridges, building structures, etc. Brief description of the drawings Figure 1 contains a schematic drawing to present the constructed invention. It shows the parts of the equipment. Figure 2 shows a real photograph of the invented equipment. Figure 3 presents an example of a flowchart of the manual tasks for revealing the microstructure using the chemical reagent called Nital, chosen for use in the manufacture of the equipment; it is known that any other reagent may be used in addition to this one chosen. Figure 4 shows the screen of the Arduino IDE compiler program containing the board's control algorithm, alcohol, acid, and water pumps, and a blower for performing chemical etching for metallography. Figure 5 shows a 23 mm diameter rebar sample with its surface hardening microstructure obtained using the manual (conventional) revelation method. Figure 6 shows the sequence of microstructure revelation performed by the automatic metallographic etching machine. Figure 7 shows the second stage of the process, focused on visualizing the microstructure using a metallographic microscope. Figure 8 shows the electrical and electronic diagram of the prototype built. Petition 870250071134, dated 12 / 08 / 2025, page 6 / 22 / 8 Description of the invention

[015] The equipment, currently manufactured in prototype form, consists of a hydraulic system that uses 5-volt fluid pumps controlled by the Arduino UNO board, which inject each fluid necessary for revealing the metal's microstructure onto the metallographic sample embedded in bakelite or resin. The prototype presented in the drawings of the previous section was assembled to perform the main metallographic chemical etching, known as Nital (3% nitric acid solution with ethyl alcohol).

[016] In the prototype there are three tanks to contain ethyl alcohol (white cap), Nital (orange cap) and potable or treated water (green cap). The system is capable of receiving as many tanks as necessary for the use of other types of reagents to perform chemical tests for any other metal to be analyzed. A container was installed to receive the residues of the acid solution, alcohol and water that interacted with the sample. The system allows, or may have in other versions, an independent disposal or reuse container.

[017] The electronic circuit consists of an Arduino UNO board or similar, a prototyping board, four relays and a button to start each chemical attack cycle.

[018] A funnel-type container was installed, containing a sieve inside and flexible ducts directed to the sample placement location, each connected to a submersible pump inside each container of nital, water and alcohol.

[019] The relays are powered with voltage from the Arduino board itself to receive the analog trigger signal from the pumps and blower controlled by the algorithm “embedded” in the electronic board.

[020] The pumps connected one to each relay are powered by a single 5-volt direct current (DC) source, and the blower is powered directly from the 127-volt alternating current (AC) mains. Petition 870250071134, dated 12 / 08 / 2025, page 7 / 22 5 / 8

[021] The prototype presented has the possibility of being completed with more reagent tanks and having the algorithm have a menu to select the type of steel or non-ferrous metal whose microstructure should be revealed for metallographic microscopy.

[022] This system is easily reproduced with the programming logic presented, using simple connections typical of the Arduino UNO standard, and the logic can also be reproduced in similar programmable logic controllers. The greatest difficulty encountered was in the programming phase in the Arduino IDE with regard to the hierarchy of the loop and cycle execution commands (executeCycle), which, if not properly shifted to the right on the IDE screen, can enter a continuous loop and not interrupt its execution at each cycle, as required by article 24 of the LPI (Industrial Property Law - Law No. 9.279 / 1996).

[023] The Arduino IDE algorithm developed for the prototype consists of the following code: loop voidO { / / Checks if the button was pressed if (digitalRead(button) == LOW && icycleActive) { activeCycle = true; / / Activates the loop executeCycleO; / / Starts the loop activeCycle = false; / / Ends the loop} void executeCycleO { / / Turn on alcohol pump #1 for 1 second to wash the sample, removing polishing impurities and water residue digitalWrite(alcohol, LOW); delay(IOOO); Petition 870250071134, dated 12 / 08 / 2025, page 8 / 22 / 8 digitalWrite(alcohol, HIGH); delay(2000); / / Waits 2 seconds for the alcohol to drain from the sample / / Turns on the Nital pump (#2) for 1 second to start revealing the microstructure digitalWrite(nital, LOW); delay(1000); digitalWrite(nital, HIGH); delay(10000); / / Waits 10 seconds for the acid to react with the sample / / Turns on the water pump (#3) for 2 seconds to neutralize the action of the Nital solution digitalWrite(water, LOW); delay(2000); digitalWrite(water, HIGH); delay(2000); / / Waits 2 seconds for the water to drain from the sample / / Turns on alcohol pump #1 for 2 seconds to remove the water that neutralized the action of Nital digitalWrite(alcohol, LOW); delay(2000); digitalWrite(alcohol, HIGH); / / Turn on the blower for 45 seconds to completely evaporate the alcohol, and the sample is ready to be analyzed under the digital metallographic microscope. Write(dryer, LOW); delay(45000); digitalWrite(hairdryer, HIGH); } Petition 870250071134, dated 12 / 08 / 2025, page 9 / 22 7 / 8

[024] This invention solves the problem of repeatability of microstructure revelation quality, laboratory safety in handling flammable and acidic products, and hazardous waste disposal, all of which are interrelated, as required by Article 22 of the LPI and Article 2, item II, of Normative Instruction No. 30 / 2013. Examples of embodiments of the invention

[025] To prove the effectiveness of the invention, a microstructure revelation test was performed on a sample of construction rebar made of carbon steel containing 0.40% carbon and 1.3% manganese, heat-treated with surface hardening. A cross-sectional section of the sample, 23 mm in diameter, was embedded in bakelite, subsequently sanded and polished with 3 µm (micron) diamond paste, and the microstructure was revealed by the manual method. This sample was polished to remove the revelation by the manual method and then inserted into the automatic machine for microstructure revelation.

[026] The results are shown in Figures 6 and 7. The microstructure revelation sequence performed by the invented automatic metallographic etching machine and presented in Figure 6 consists of: (1) Sample without microstructure revelation before being inserted into the machine, (2) Demonstration of the sample's "mirrored" surface, (3) Placement in the machine receptacle, (4) Ready to start development, (5) Machine activation, (6) Application of alcohol, (7) Application of 2% Nital solution, (8) Waiting time for microstructure revelation, (9) Removal of Nital solution with water, (10) Removal of water with alcohol, (11) Start of drying with hot air blast, Petition 870250071134, dated 12 / 08 / 2025, page 10 / 22 / 8 (12) completion of drying, (13) removal of the sample with the microstructure revealed and (14) sample ready for observation under the metallographic microscope.

[027] To achieve the microstructure revelation, the following steps were performed, as shown in Figure 7: (1) An Olympus GX51 metallographic microscope was made available to observe the quality of the development, (2) An image was taken showing the tempered region and the region below the temper, (3) The tempered region was photographed showing the martensite microstructure resulting from the tempering, (4) The internal region of the material was photographed without the effect of tempering, and (5) The microstructure formed by pearlitic grains surrounded by ferritic grain boundaries was photographed. Petition 870250071134, dated 12 / 08 / 2025, page 11 / 22

Claims

1 / 2 CLAIMS 1. Automatic machine for revealing metal microstructures, characterized by comprising: a support structure configured to receive a polished metal sample; at least three reservoirs, containing respectively: developing solution, alcohol and water; an electronically controlled pumping system for dosing the fluids onto the sample; an electronic control unit based on a microcontroller, programmed to execute automatic development cycles according to defined parameters of time and application sequence; a drying system that operates after the application of the fluids; a compartment for collecting chemical residues from the development.

2. Machine according to claim 1, characterized by having an Arduino UNO microcontroller or equivalent.

3. Machine according to claim 1, characterized by including a menu on a digital or analog display for selection and adjustment of the development program, adaptable to different types of metals and reagents.

4. Machine according to claim 1, characterized by having a pumping system comprising submersible or non-submersible direct current fluid pumps controlled by relays.

5. Machine according to claim 1, characterized by having a drying system consisting of a hot air blower attached to the structure.

6. Machine according to claim 1, characterized by including presence or position sensors for the sample to ensure the safe operation of the automatic cycle.

7. Machine according to claim 1, characterized by allowing the selective disposal or reuse of fluids used in the developing process. Petition 870250071134, dated 12 / 08 / 2025, page 12 / 22 2 / 2 8. Machine according to claim 1, characterized by using or not using solution storage tanks. Petition 870250071134, dated 12 / 08 / 2025, page 13 / 22

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