Method for detecting contaminants on steel parts by ultraviolet light

Abstract

The present invention provides methods and apparatus for detecting contaminants on cold-formed steel parts prior to press hardening, where contaminants on the cold-formed steel parts are likely to be problematic. The methods and apparatus are also used to detect contaminants on cold-forming machinery that may be transferred to the cold-formed steel parts during the cold-forming process. In some aspects, the present invention also provides methods and apparatus for detecting cracks or fissures on cold-formed steel parts prior to press hardening. Both of these methods and apparatus utilize ultraviolet light to detect contaminants, cracks, or fissures.

Description

Technical Field

[0001] The present invention relates to methods and apparatus for detecting contaminants on cold-formed steel parts prior to press hardening, where contaminants on the cold-formed steel parts are likely to be problematic. The methods and apparatus are also used to detect contaminants on cold-forming machinery that may be transferred to the cold-formed steel parts during the cold-forming process. In some aspects, the present invention also relates to methods and apparatus for detecting cracks or fissures on cold-formed steel parts prior to press hardening. Both of these methods and apparatus utilize ultraviolet light to detect contaminants, cracks, or fissures. Background Art

[0002] It is known that structural components of motor vehicle bodies are produced from hardened steel components, making the motor vehicle body particularly strong.

[0003] The hardened steel components are typically manufactured by two conventional methods: i) heating, austenitizing, hot forming and hardening a steel sheet blank; or ii) cold forming the steel sheet to produce the component, which is then heated and quench-hardened in a tool having a profile or shape that matches the component.

[0004] In both conventional methods, the steel plate is typically hardened by heating it in a furnace. Heating causes the steel to transform from the ferrite phase to the austenite phase, while subsequent controlled rapid cooling, or quenching, causes the steel to transform from the austenite phase to the hard martensite phase. Because the temperatures within the furnace are very high (sometimes exceeding 900°C), the furnace atmosphere affects the surface of the heated steel, regardless of the heating method used.

[0005] This is particularly important when using galvanized steel billets. Due to the presence of small amounts of oxygen-affinity elements, an oxide layer may form on the surface of the zinc layer. When the galvanized steel part is heated in the furnace, the oxide layer helps protect the underlying zinc layer. Without this protective oxide layer, the zinc layer could evaporate or burn away.

[0006] It will be appreciated that oxidation may occur on the surface of the steel slab or cold-formed steel component even when the surface is not galvanized, coated with a material other than zinc, or not coated at all.

[0007] Alloying elements in steel, such as iron and manganese, can cause surface oxidation. In the case of coated steel, the coating reacts with the steel. Besides the coating components, alloying elements of iron and steel can also cause surface oxidation. In galvanized steel, alloying elements in the zinc layer can also oxidize. In particular, oxygen-affinity elements, such as aluminum, can form AlO or Al₂O₃ layers. These can also form manganese oxide, zinc oxide, or mixed oxide layers on the surface of galvanized steel.

[0008] Suitable steels for quench hardening processes include steel alloys containing manganese and boron well known to those skilled in the art. For example, steels with the known steel grades 22MnB5 or 20MnB8 are suitable, although other types of steel may also be suitable.

[0009] The oxide layer formed during the heating process will affect subsequent processes such as welding, bonding, and painting.

[0010] Optionally, after the heat treatment, the oxide layer may be completely or partially removed by sandblasting or the like. Summary of the Invention

[0011] The inventors of the present invention have discovered that certain forms of contaminants on the surface of cold-formed steel parts prior to press quenching, such as fingerprints or oils or debris from the cold-forming process (e.g., zinc particles shed from a galvanized steel sheet blank), can cause unwanted blooming and other defects in the finished product during the press quenching process. It is currently believed that these forms of contaminants interfere with or prevent the formation of a protective oxide coating on the contaminated areas of the steel sheet part, which can cause the underlying zinc layer of the galvanized steel to evaporate or burn away. In addition to producing an unsightly "bloom" on the surface of the steel sheet part, the damaged areas of the zinc layer of the steel sheet part are also susceptible to corrosion.

[0012] Viewed from a first aspect, the present invention provides a method of detecting contaminants on a steel component prior to austenitizing and press hardening treatments, wherein the steel component is exposed to ultraviolet light to highlight contaminants on the surface of the steel component.

[0013] Viewed from a second aspect, the present invention provides an apparatus for detecting contaminants on a steel component prior to austenitizing heat treatment and press hardening, the apparatus comprising a detection space and an ultraviolet light source for irradiating the detection space with ultraviolet light.

[0014] Viewed from a third aspect, the present invention provides a method of detecting contaminants on steel cold forming machinery, wherein at least a portion of the steel cold forming machinery is exposed to ultraviolet light to highlight contaminants on a surface of the at least a portion.

[0015] In some embodiments, the steel component is a cold-formed steel component. That is, the steel component is subjected to a cold forming process prior to a heating process (e.g., in a furnace) to convert the steel to an austenite phase, and then to a quenching process to convert the steel to a martensite phase.

[0016] In other embodiments, the steel component is a steel sheet blank that is subsequently heated to convert the steel to an austenite phase, hot formed, and quenched to convert the steel to a martensite phase.

[0017] The steel component can be a galvanized or aluminum-plated steel component with a metal anti-corrosion layer, in particular a zinc layer, a zinc-based alloy layer, an aluminum layer, or an aluminum-based alloy layer. The zinc-based alloy is Galfan, Galvalume, Galvannealed, ZnMg, ZnCr, ZnNi, or ZnMgNi, and the aluminum-based alloy layer is made of aluminum silicon, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The embodiments of the present invention will be further described below with reference to the accompanying drawings, in which:

[0019] Figure 1 This is a process flow chart of an embodiment of the present invention;

[0020] Figure 2a is a contour image of a contaminated area on a cold-formed steel component of the present invention;

[0021] Figure 2b Shown in more detail Figure 2a A contaminated area, the contaminated area being a fingerprint;

[0022] Figure 2c for Figure 2a and 2b Schematic diagram of the contaminated area under ultraviolet light;

[0023] Figure 3a A close-up view of contaminants on a mold of a cold forming machine of the present invention;

[0024] Figure 3b Schematic diagram of contaminants on a mold of a cold forming machine of the present invention under ultraviolet light irradiation;

[0025] Figure 3c for the reason Figure 3a Schematic diagram of a cold-formed steel part formed by a cold-forming machine, showing how contaminants are transferred from the cold-forming machine's mold to the cold-formed steel part under ultraviolet light.

[0026] Figure 3d is a schematic diagram of a cold-formed steel component after austenitizing and quenching, wherein contaminants on the steel component cause defects or blooming on the surface of the steel component;

[0027] Figure 4 A schematic diagram of an ultraviolet inspection box according to an embodiment of the present invention;

[0028] Figure 5 A chart including UV light types and differences;

[0029] Figure 6 This is the experimental test result diagram. DETAILED DESCRIPTION

[0030] Aspects of the present invention have the surprising effect that many forms of contamination on steel parts that are not easily visible to the naked eye under white light can cause blooming and other contamination defects on the steel parts during subsequent austenitizing and press hardening processes, however, the contamination is more easily identified under ultraviolet light.

[0031] These contaminants include fingerprints, dirt, dust, zinc flakes generated when cold forming galvanized steel sheet blanks, salts from human sweat, and dirty or contaminated or incompatible oils from cold forming machinery.

[0032] UV light can be used to inspect steel parts before austenitizing and press hardening. UV light causes contaminants such as fingerprints, dirt, dust, zinc flakes, salts from human sweat, and dirty, contaminated, or incompatible oils to fluoresce or glow, making it easier for operators to identify and remove potential contaminants before austenitizing and press hardening.

[0033] UV light can also be used to inspect components of cold forming machinery, such as cold forming dies and die cavities, to detect contaminants that may have been transferred to the surface of the steel component during cold forming.

[0034] Alternatively or additionally, UV light may be used to highlight cracks, fissures or other defects in cold-formed steel parts that are not readily visible to the naked eye and that could cause manufacturing defects during the subsequent press hardening process.

[0035] As mentioned above, contaminants on the surface of steel components can interfere with or hinder the formation of a protective oxide layer on the steel surface. This protective oxide layer is particularly important during the austenitizing process of galvanized steel components, as it reduces the risk of the zinc layer evaporating or burning off the steel component when heated to high temperatures. Localized defects in the protective oxide layer can cause unwanted blooming and other damage to the underlying steel component during austenitizing and subsequent press hardening.

[0036] Embodiments of the present invention are particularly advantageous in processes where steel slabs are cold-formed prior to subsequent austenitizing and press-hardening processes. This is because cold-formed steel parts prior to austenitizing are typically handled manually rather than robotically, which carries the risk of contaminants such as fingerprints and sweat being present on the cold-formed steel parts.

[0037] Advantageously, the UV light is generated by a black light source that emits primarily UV light and also emits little or no visible light. In many applications, UV light with a wavelength in the range of about 315 to 400 nm (long-wave ultraviolet, UV-A) is most suitable, although in some applications, UV light with a wavelength in the range of about 280 to 315 nm (medium-wave ultraviolet, UV-B) is useful.

[0038] The inventors have determined that different wavelengths of UV light are required for reliable detection and inspection, depending on the metal layer of the steel substrate. The most difficult deposits to detect are fingerprints. Figure 5 ), it turned out that UV-A light was the most suitable, while UV-C (short-wave ultraviolet) light was still sufficiently suitable. For example, such a coating could be a Z140 zinc layer (hot-dip galvanized with 140 g / m² of zinc) on a 22MnB5 steel substrate. Later, it was shown that for 22MnB5 steel substrates coated with aluminum silicon (AlSi), both UV-A and UV-C were ineffective, while only UV-B was effective.

[0039] Certain embodiments of the present invention are particularly effective at highlighting salt (sodium chloride) from sweat or fingerprints on steel parts, for example, when operators do not wear the correct type of gloves to handle the steel parts before or after cold forming. Salt deposits on steel parts after austenitizing and press hardening can cause unsightly blooming on the steel surface. In some cases, the blooming can be so severe that it causes structural defects in the surface. Salt fluoresces significantly under ultraviolet light, allowing quality control personnel to identify the location of salt contamination and take corrective cleaning measures. The efficacy of the cleaning action can also be verified under ultraviolet light.

[0040] Certain embodiments of the present invention are particularly effective at highlighting dust or dirt on steel components prior to austenitizing and press-hardening. Dust or dirt contamination on steel components can cause unsightly blooming on the steel surface after austenitizing and press-hardening. In some cases, blooming can be so severe that it can cause structural defects on the surface. Dust or dirt fluoresces significantly under UV light, allowing quality control personnel to identify the location of dust or dirt contamination and initiate corrective cleaning measures. The effectiveness of the cleaning action can also be verified under UV light.

[0041] Certain embodiments of the present invention are particularly effective at removing zinc flakes from steel parts prior to austenitizing and press-hardening. Zinc flakes are produced during cold forming of galvanized steel and can cause an unsightly blooming of the steel surface after austenitizing and press-hardening. In some cases, blooming can be so severe that it can lead to structural defects in the surface. Zinc flakes fluoresce significantly under ultraviolet light, allowing quality control personnel to identify the location of the zinc flakes and initiate corrective cleaning measures. The effectiveness of the cleaning action can also be verified under ultraviolet light.

[0042] Certain embodiments of the present invention are particularly effective at highlighting oil contaminants on steel parts prior to austenitizing and press-hardening. Oil contaminants, such as dirty or incompatible oils from cold-forming machinery, can cause unsightly blooming on the steel surface after austenitizing and press-hardening. In some cases, blooming can be so severe that it can cause structural defects in the surface. Oil contaminants fluoresce strongly under UV light, allowing quality control personnel to identify the location of the contamination and initiate corrective cleaning measures. The effectiveness of the cleaning action can also be verified under UV light.

[0043] A surprising advantage of certain embodiments is that different types of contaminants can be more easily distinguished from one another under UV light than under white light. This can be a significant advantage because different types of contaminants require different removal methods. For example, sodium chloride in human sweat is insoluble in organic solvents such as alcohol and therefore requires water or other aqueous solvents to remove from steel surfaces. In contrast, oily or grease contaminants are best removed using alcohol or other organic solvents. Therefore, embodiments of the present invention can determine the type of contaminant and select the appropriate cleaning solution.

[0044] Certain embodiments of the present invention are particularly effective at highlighting cracks or fissures in cold-formed steel parts. These cracks or fissures may arise from defects in the steel sheet stock. Surprisingly, it has been found that illumination under UV light significantly improves contrast and enhances the visibility of these cracks or fissures compared to illumination under white light.

[0045] In certain embodiments, an inspection station may be provided in the form of a UV light box. The UV light box may include a workbench provided with a canopy, the workbench and the canopy defining an inspection space within which the steel sheet blanks and / or cold formed steel parts may be placed. The canopy may be combined with one or more UV light sources for emitting UV light into the inspection space. For example, the one or more UV light sources may be mounted on or incorporated into one or more interior surfaces of the canopy. The canopy is used to shield multiple sides of the inspection space from stray ambient light to more easily observe the fluorescence of contaminants, while still providing access to the inspection space by working in front of the inspection station. The UV light box may be located at the end of a cold forming line to facilitate inspection of steel parts prior to austenitizing and press hardening processes.

[0046] In certain embodiments, UV light is used to inspect components of cold forming lines, such as the surfaces of cold forming dies. Cold forming dies can become contaminated by fingerprints, sweat, contaminated or incompatible oils, zinc flakes, dirt, or dust, which can transfer to cold-formed steel components. Inspecting these components of cold forming lines under UV light can more easily detect contaminants and verify that the cleaning process has indeed removed them.

[0047] Embodiments of the present invention can be easily incorporated into steel processing lines and provide a safe, simple, and cost-effective way to detect contaminants.

[0048] The steel components may be inspected manually under UV light, for example at the inspection station described above.

[0049] Alternatively or additionally, image processing techniques can be used to automatically inspect steel parts under UV light. For example, one or more cameras can be used to collect images of the steel parts under UV light, and the images can be processed by a computer using known image processing techniques to identify the location of any contaminated areas. In some embodiments, the type of contaminant can also be identified. The computer can indicate the location and, optionally, the type of contaminant to an operator so that the steel parts can be cleaned. In some embodiments, the computer can control a robotic cleaning mechanism to perform appropriate automated cleaning actions. In some embodiments, steel parts can be placed on a conveyor and passed through an inspection station that includes a canopy defining an inspection space, one or more UV light sources, and one or more cameras. The canopy helps shield the inspection space from ambient light, allowing the one or more cameras to more easily observe UV fluorescence. The one or more cameras are connected to a computer running appropriate image processing software. The computer can also control the one or more cameras and the one or more UV light sources to obtain image data from all surfaces of the steel parts. In some embodiments, the one or more UV light sources can include UV light sources that generate different wavelengths to better identify and distinguish different types of contaminants. After passing the inspection station, contaminated steel parts can be automatically removed from the conveyor for cleaning and subsequent re-inspection.

[0050] In some embodiments, it is not necessary to manually or automatically inspect every galvanized steel part. It may be sufficient to inspect only a representative sample of galvanized steel parts on a production line to achieve improvements in avoiding blooming and other defects.

[0051] Figure 6 The table shows the experimental test results of the present invention. Ten samples (S1 to S10) of cold-formed galvanized steel parts were prepared. Some of the samples were deliberately contaminated with fingerprints and / or sodium chloride. The contaminants could not be distinguished under ambient white light illumination. According to the present invention, three different human operators OP1, OP2 and OP3 inspected the samples under ultraviolet light according to the present invention. The results show that when contaminants were present, all operators correctly identified the location and type of contaminants. Only twice, when no contaminants were present, did the operators mistakenly identify a specific type of contaminant when it was not actually present. However, it can be understood that false positive identifications are less problematic than false negative identifications.

[0052] refer to Figure 1, from left to right, shows a series of processing steps in an embodiment of the present invention. First, a galvanized steel sheet blank 1 is cut from a galvanized steel coil 2. Second, the galvanized steel sheet blank 1 is cold-formed into the desired galvanized steel component 3 using a cold-forming die 4. Third, the cold-formed galvanized steel component 3 is inspected for contaminants under ultraviolet light from a UV or blacklight source 5. If contaminants are determined to be present, the cold-formed galvanized steel component 3 is cleaned to remove the contaminants and re-inspected using ultraviolet light from the blacklight source 5. Fourth, the cold-formed steel component 3 (contaminant-free) is placed in a heating furnace 6 and heated until the temperature within the heating furnace 6 is sufficient to transform the steel into the austenite phase. This temperature may exceed 900°C. Preferably, this temperature is above the Ac3 temperature for the specific steel composition to ensure complete or near-complete austenitization. Fifth, the austenitized steel component 3 is placed in a suitably configured die or former 7 and then rapidly quenched to promote the steel's transformation to the martensite phase. This step is also known as press quenching. Placing the steel component 3 in the die or former 7 helps reduce quenching distortion during rapid cooling. Finally, a sixth step of surface treatment is optionally performed, such as wheel blasting with a suitable abrasive 8. The surface treatment step can be used to remove unwanted oxide layers from the surface of the steel component 3 or to smooth out rough edges.

[0053] Figure 2a Shown are traces of contamination 9 on a galvanized steel component 3 after cold forming but before austenitizing and press hardening. Figure 2b The contamination mark 9 is shown in more detail. In this case, the contamination mark 9 is caused by the operator's fingerprint. Fingerprints contain sodium chloride from sweat, which interferes with the formation of a protective oxide layer on the steel component 3. The contamination mark 9 is difficult to see under normal or ambient white light conditions. Figure 2c The contaminant trace 9 is shown under UV or black light illumination. As shown by the fluorescent area 10, the UV or black light illumination causes the contaminant trace 9 to produce a significant sodium chloride fluorescence, thereby enabling the contaminant trace 9 to be quickly identified and removed from the surface of the steel component 3 before austenitizing and press hardening.

[0054] Figure 3a 1 is a close-up view of the outline of a contaminant trace 9 on a mold 20 of a cold forming machine of the present invention under normal or ambient white light conditions. Under this condition, the contaminant trace 9 is almost or completely invisible.

[0055] Figure 3b Schematic diagram of contaminant traces 9 on a mold 20 of a cold forming machine 21 under ultraviolet light. As can be seen, the contaminant traces 9 are very obvious under ultraviolet light.

[0056] Figure 3c for the reason Figure 3aA schematic diagram of a cold-formed steel component 3 formed by a cold-forming machine die 20 before austenitizing and under UV light shows how contaminants are transferred from the cold-forming machine die 20 to the cold-formed steel component 3 during the cold-forming process. Contaminants can include sodium chloride from human sweat, fingerprints, oil, grease, zinc flakes, or other forms of contaminants. Contamination marks 9 on the cold-formed steel component 3 are clearly visible under UV light.

[0057] Figure 3d Schematic diagram of a cold-formed steel component 3 after austenitizing and quenching, wherein contaminants on the steel component 3 may cause surface defects or bloom 22 on the steel component 3. The surface defects or unsightly bloom 22 may represent weaknesses in the protective zinc layer of the galvanized steel component or weaknesses where the protective zinc layer is missing from the galvanized steel component, thereby making the steel component susceptible to corrosion.

[0058] Figure 4 The device for detecting contaminants on a steel component before austenitizing heat treatment and press-quenching treatment according to an embodiment of the present invention includes a detection space and an ultraviolet light source for irradiating the detection space with ultraviolet light.

[0059] Figure 4 The apparatus shown in FIG. 1 includes an inspection station in the form of a UV light box 30. The UV light box 30 may include a workbench 31 provided with a canopy 32, the canopy 32 and the workbench 31 defining an inspection space 33, wherein a steel sheet blank or steel component 3 may be placed in the inspection space 33. The canopy 32 may incorporate one or more UV light sources 34 for emitting UV light into the inspection space 33. The one or more UV light sources 34 are mounted on or incorporated into one or more inner surfaces of the canopy 32. The canopy 32 serves to shield several sides of the inspection space 33 from stray ambient light so that contaminant fluorescence can be more easily observed, while still providing access to the inspection space 33 by an operator working in front of the inspection station. The UV light box 30 may be located at the end of a cold forming line to facilitate inspection of the steel component 3 prior to austenitizing and press hardening processes.

[0060] Throughout the present specification and claims, the words "comprise" and "comprising" and their variations all mean "including but not limited to," and they are not intended to (and are not used to) exclude other components, additives, assemblies, integers, or steps. Throughout the present specification and claims, the singular includes the plural, unless the context requires otherwise. In particular, where the indefinite article is used, the specification will be understood to contemplate the plural as well as the singular, unless the context requires otherwise.

[0061] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All features disclosed in the specification (including any accompanying claims, abstract and drawings), and / or all steps of any method or process disclosed herein, may be combined in any combination, except where at least some of such combinations of features and / or steps are mutually exclusive. The invention is not limited to the details of any foregoing embodiments. The invention extends to any one novel feature or any novel combination of features disclosed in the specification (including any accompanying claims, abstract and drawings), or any one novel feature or any novel combination of features disclosed in any method or process step.

[0062] Note that all papers and documents filed concurrently with or before the present specification and which are open to public inspection with this specification are hereby incorporated by reference into this specification.

Claims

1. A method for detecting contaminants on a steel component or cold forming machinery prior to austenitizing and press hardening, wherein the steel component is exposed to ultraviolet light to highlight contaminants, cracks or fissures on the surface of the steel component and / or the cold forming machinery is at least partially exposed to ultraviolet light, characterized in that The steel component is coated with a metal layer; The steel parts and / or cold-formed machinery are exposed to ultraviolet light to highlight contaminants or cracks or fissures on the surface of the steel parts, wherein long-wave ultraviolet light and short-wave ultraviolet light are used to detect steel parts coated with a zinc layer or a zinc-based alloy layer, or long-wave ultraviolet light and short-wave ultraviolet light are used to detect cold-formed machinery, wherein the long-wave ultraviolet light has a wavelength of 315 to 400 nm and the short-wave ultraviolet light has a wavelength of 100 to 280 nm; The steel parts and / or cold forming machinery are exposed to ultraviolet light to highlight contaminants, or to highlight cracks or fissures on the surface of the steel parts, wherein medium-wave ultraviolet light is used to detect steel parts coated with an aluminum layer or an aluminum-based alloy layer, or medium-wave ultraviolet light is used to detect contaminants on cold forming machinery, wherein the medium-wave ultraviolet light has a wavelength of 280 to 315 nm.

2. The method according to claim 1, wherein the steel component is coated with a zinc layer, a zinc-based alloy layer, an aluminum layer, or an aluminum-based alloy layer, the zinc-based alloy layer is made of galvanneal, aluminum-zinc-silicon, alloyed hot-dip galvanneal, ZnMg, ZnCr, ZnNi, or ZnMgNi, and the aluminum-based alloy layer is made of aluminum-silicon.

3. The method of claim 1, wherein the steel component is a cold-formed steel component.

4. The method of claim 1, wherein the ultraviolet light is used to cause the contaminants to fluoresce.

5. The method of claim 1, wherein the contaminant comprises at least one of fingerprints, dirt, dust, flaky zinc powder, salt in human sweat, grease, and oil. The method according to claim 1 , wherein the types of pollutants are distinguished based on their fluorescence under ultraviolet light.

7. The method of claim 1, wherein different cleaning solutions are selected according to the determined types of contaminants to clean contaminants from the cold forming machine or a part of the cold forming machine, and / or the surface of the steel part.

8. The method of claim 1 , wherein the contaminants detected on a portion of a cold forming machine are removed to avoid transfer of the contaminants to the cold formed steel part and improve blooming of the cold formed steel part during a subsequent press hardening process, and / or the contaminants detected are removed from the steel part before austenitizing and press forming to improve blooming of the steel part during austenitizing and press hardening processes.

9. The method of claim 1, providing a black light source to generate the ultraviolet light.

10. The method of claim 1 , comprising collecting at least one image of the cold forming machine or a portion of the cold forming machine and / or the steel component under ultraviolet light by at least one camera, and identifying contaminants or cracks or fissures on the surface of the steel component by running image processing software on a computer.

11. A device for detecting contaminants on a steel part or cold forming machinery before austenitizing and press hardening, wherein the steel part is exposed to ultraviolet light to highlight contaminants, cracks or fissures on the surface of the steel part, and / or the cold forming machinery is at least partially exposed to ultraviolet light, characterized in that The device comprises: a detection space and an ultraviolet light source, wherein the ultraviolet light source is used to irradiate the detection space with long-wave ultraviolet rays, and / or medium-wave ultraviolet rays, and / or short-wave ultraviolet rays. The steel component is coated with a metal layer; The steel parts and / or cold-formed machinery are exposed to ultraviolet light to highlight contaminants or cracks or fissures on the surface of the steel parts, wherein long-wave ultraviolet light and short-wave ultraviolet light are used to detect steel parts coated with a zinc layer or a zinc-based alloy layer, or long-wave ultraviolet light and short-wave ultraviolet light are used to detect cold-formed machinery, wherein the long-wave ultraviolet light has a wavelength of 315 to 400 nm and the short-wave ultraviolet light has a wavelength of 100 to 280 nm; The steel parts and / or cold forming machinery are exposed to ultraviolet light to highlight contaminants, or to highlight cracks or fissures on the surface of the steel parts, wherein medium-wave ultraviolet light is used to detect steel parts coated with an aluminum layer or an aluminum-based alloy layer, or medium-wave ultraviolet light is used to detect contaminants on cold forming machinery, wherein the medium-wave ultraviolet light has a wavelength of 280 to 315 nm.

12. The apparatus according to claim 11, wherein the inspection space is defined by a workbench and a ceiling.

13. The device of claim 11, wherein the ultraviolet light source is disposed on an inner surface of the canopy.

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