JP2720320B2 - Protection coating application method and protection element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method of applying a protective coating on a carrier member, and more particularly to a method in which at least one protective plate is integrally connected to an installation surface formed on the carrier member. Such a method for producing a protection element for a test device. Furthermore, the invention relates to a protective element having a carrier member and at least one holding plate integrally connected to the carrier member.

[0002]

BACKGROUND OF THE INVENTION In many applications where the problem of protecting sensitive components from damage exists, at least one of the materials used is particularly resistant to damaging effects during use. A protective element made of many materials is used. In most cases, there is the problem of complementing the optimal protection function with other optimal functions.

An example of the necessary interlock between the protection function and the use function of the protection element is to protect the magnetic stray or leakage flux probe against mechanical damage in a test device having a rotating test probe. This is the protection element used. In such a test apparatus, a test head having a test probe is slid or dragged along a helical path above the surface of a test object having a circular cross section, for example, on the outer surface of a metal tube. The sensitivity of this method increases with decreasing distance between the test surface and the test tip, and this distance should typically be less than 1 mm. Therefore, the protection element in the vicinity of the test tip of such a device must on the one hand be as thin as possible, but on the other hand it is generated by dragging in order to allow a long service life of the test equipment without replacing the protection element. It must be able to withstand the most frictional wear for the longest time possible. In some situations, the protective element must also be able to withstand damage and impacts caused by surface irregularities of the test object without damage. It should also be noted that the protective element, on the one hand, is subject to thermal stresses due to frictional heat, but in modern test equipment is also subjected to thermal stresses due to the significant increase in magnetic flux leakage energy, resulting in significant heating of the test head and test material. Should.

In a test device of the known type near the test head, the protective element comprises a Remanit carrier plate having a circular passage opening, which plate has a thickness of 2-3 / 10 mm of 1 mm on one side. The hard metal having the hardness is fixed. The protective element is positioned relative to the test probe such that the test probe is partially inserted into the passage opening and is only about 0.1 mm from the inside of the hard metal plate during assembly of the device. For a sliding test head, the distance between the test probe and the surface of the test material is less than 1 mm.

[0005]

Bonding techniques are no longer adequate at test head operating temperatures above 100 ° C., since these temperatures constitute a mechanical load limit for typical adhesives. When joining the carrier member and the guard plate by soldering, in particular by brazing, a problem of deflection arises, which depends on the wide range of coefficients of thermal expansion of the materials used for the carrier member and the guard plate. Therefore, in the case of heating, the hard metal protective plate expands almost half as much as a special steel carrier member.
In the case of a connection between two elements caused by soldering, a stress is generated upon cooling from the soldering temperature, and this stress may cause the protection plate and the carrier member to bend. Protective elements having precisely defined geometries required to ensure a precise spacing between the test stylet and the test material in the test apparatus described above cannot be manufactured in this manner. In general, continued straightening of the flexed protection element will result in hard metal breakage and consequently render it unusable.

[0006] It is an object of the present invention to provide a method which makes it possible to substantially avoid the problem of deflection and to provide a thermally stable connection or joining of materials having different thermal expansion responsive properties. is there. It is another object of the present invention to provide a thermally stable and geometrically stable protective element formed from a combination of materials having different coefficients of thermal expansion.

[0007]

In order to solve the above-mentioned problems, a first invention of the present application is a method of installing a protective coating on a carrier member (26), in particular, at least one protective plate (27). ) Is manufactured in such a way that the protection plate (27) is integrally connected with the mounting surface formed on the carrier member (26). And the carrier member (26), the protection plate (27) and the counter member (29) are heated, and the carrier member (26), the protection plate (27), and the protection plate ( 27) and the counter member (29) are at least partially joined together by one solder layer at the same time by the soldering process, and when the solder layer crystallizes, the counter member (29) and the counter member (29) The solder layer holding the record is summarized as a method which is characterized to be removed from the protective plate (27).

According to a second aspect of the present invention, there is provided a protection element having a carrier member (26) and at least one protection plate (27) integrally connected to the carrier member (26). ) Are at least partially particularly plane-parallel to the substantially planar mounting surface
7) is soldered with hard solder, and the protection plate (2)
7) The surface of the outer region remote from the carrier member (26) is a surface formed by removing the counter member (29) and the related solder layer, for example, by polishing. The gist of the protection element is as follows.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for installing a protective coating on a carrier member, in which at least one protective plate is integrated with an installation surface formed on the carrier member. In a method for producing a protective element for a test device, and a protective element having a carrier member and at least one protective plate integrally connected to the carrier member, the problem is solved as follows.

In accordance with the present invention, a protective coating is applied to the carrier member and at least one protective plate is integrally connected to the preferably planar mounting surface of the carrier member, which is mounted in a sandwich manner. A protection plate is held between the surface and the counter member, and as the carrier member, the protection plate and the counter member are subsequently heated, the carrier member and the protection plate and the protection plate and the counter member are simultaneously at least partially ( The counter-member and this counter-member are joined together by soldering, following the crystallization (solidification) of the solder layer, ie, in the case of conventional soldering, following a partial cooling from the soldering temperature. Can be manufactured such that the solder layer holding the metal is removed from the protective plate. It is particularly suitable as a protective element for test equipment.

The protection plate is preferably installed and fixed between the installation surface and the counter member at ambient temperature. The holding of the individual components on the other component can be suitably effected in such a way that the components can freely expand upon heating according to their different coefficients of thermal expansion. Thus, the members can be fixed to one another in a substantially central part, in particular in one part, so that the outer regions of the superposed members can move relative to one another when inflated. Next, with the uniform heating of the entire device consisting of the carrier member, the protection plate and the counter member, these members are individually brought into contact by the solder material brought into contact with the device due to the force of the capillary. Can be heated in such a manner as to be able to enter between the elements or members. This method is preferably performed particularly under an inert gas atmosphere. Soft or hard solder can be used as the solder material. In the case of soft soldering, thermal post-treatment of the solder layer may be appropriate. Particularly, hard solder such as silver hard solder is desirable.

Crystallization of the solder layer occurs between the installation surface of the carrier member and the protection plate or between the protection plate and the counter member,
The above-mentioned plurality of members are firmly joined as an integral structure. Crystallization of the solder layer conventionally occurs during cooling from the soldering temperature, but may also occur partially at the soldering temperature. The different coefficients of thermal expansion of the materials during cooling can cause stress to form in the individual materials.
At that time, a material having a high coefficient of thermal expansion receives a tensile stress, while a material having a low coefficient of thermal expansion (generally, a protective plate) receives a compressive stress.

On the other hand, in the case of a protective plate which is freely soldered to the carrier member, the compressive stress acts on one side of the protective plate, so that an asymmetrical stress is produced, and in the method according to the invention, the carrier member also has an asymmetrical stress. The stress ratio in the protective plate during cooling is significantly different from the ratio in the freely soldered protective plate, as it also occurs on the opposite mating plate. The stress ratio on both sides of the protective plate can be made particularly symmetric. During the soldering process and during the cooling process, the counter member can provide a supplementary effect that has certain effects on the properties of the protective plate.

Following the crystallization of the solder layer, ie, usually following the cooling of the equipment, according to the present invention, the counter member and the solder layer holding the counter member can be removed from the protective plate. For removal purposes, material removal methods such as etching, milling or sand blasting can be used. Preferably, the counter member and the solder layer holding the counter member are removed from the protective plate by polishing. The polishing action allows the creation of external geometries on the protection element which are preferred or which can be adapted to the geometry of the mounting point.

The protection element for protecting the test probe sliding or dragging in the abrading slide should be resistant to its abrasion resistance, ie to withstand material removal occurring on the slide due to polishing. The most suitable one can be selected. It is also important that the material of the guard plate is selected so that it has less influence on the measurements that occur through the material.
Therefore, the protective plate material must not be ferromagnetic and must be a conductor with low conductivity. Therefore, a protection plate made of a ceramic material can be used. It is preferred to use a protective plate made of wear-resistant, hard or hardened metal, preferably hard metal or carbide. Hard metal protective plates made by powder metallurgy ensure a long service life, on the one hand, especially for test heads that exhibit abrasion resistance, and, on the other hand, the metal plate is exposed to weak shocks. It should not be brittle enough to break easily.

The fixed protective plate made of, for example, hard metal has a small crack after the above-mentioned operation. This may be due to the presence of many critical defects in the underlying non-uniform material and the fact that in the case of mechanical loading, it can lead to the formation and propagation of cracks. Surprisingly, the number of cracks is significantly reduced in the case of a hard metal plate of the same composition, which is soldered to the carrier member in the method according to the invention, as compared to the case of a protection plate fixed in a conventional manner. It has been found. This may be due to the special stress ratio mentioned above in the protective plate which is soldered according to the invention. As a result of the soldering of the counter plate, it is possible that there is a change in composition on the side of the protective plate far from the carrier member in the area close to the surface. This makes the formation of cracks on the surface more difficult, which may explain the reduced cracking of the soldered protection plate according to the invention. The reduced cracking of protective elements manufactured according to the invention helps to provide a longer service life than conventionally secured protective elements of the same thickness. Good wear behavior which gives a long service life can also be obtained by penetrating the solder material into the hard metal seizure and by improving the surface structure.

The use according to the invention of the counter member during the soldering of the protective plate to the carrier member can also be used to produce a protective element having a specific desired surface curvature. This can be achieved by making the carrier member and the counter member mutually correspond to the thermal expansion configuration. It is particularly advantageous that the carrier member and the counter member are made of the same material. With an appropriate counter member thickness, substantially the same stress ratio occurs on both sides of the guard. This substantially symmetrical stress distribution ensures that no stresses are created which cause bending inside the sandwich structure formed by the carrier member, the protective plate and the counter member, especially during temperature changes during cooling from the soldering temperature. Depends on This can be particularly important for flexible carrier members.

The counter member is provided with at least one planar surface for the purpose of soldering onto a suitably planar and parallel protective plate. Preferably, the counter member is configured as a planar parallel counter plate, which can be easily manufactured by cutting or punching from a flat material. The use of flat and parallel counter plates facilitates the placement and fixing of the sandwich structure.

It is also possible to install the protection plate on the following carrier member. It is the actual protective plate and, optionally, a carrier member configured as a planar and parallel plate similar to the counter member. Following the removal of the counter element, such a protective element now consists essentially of the two materials on its entire surface area. Such a protection element can be used wherever it needs protection against mechanical wear and optionally impact.

In special cases where the thickness of the protective element plays an important role, ie a sensitive test probe must be brought close to the test object and at the same time protected against mechanical damage. In this case, it is advantageous if the carrier element has at least one passage opening which can be completely protected by the protective plate. Therefore, only the thickness of the protection plate near the passage opening determines the thickness of the protection element. The material of the carrier member, which preferably surrounds the circular passage opening, is used for the purpose of monolithic attachment of the protective plate to the carrier member. The thickness of the protective plate, and thus, for example, the distance between the test probe and the test material indirectly, can be adapted in a manner suitable for the test function in the case of a carrier member having a passage opening.

Compared to the case of a fixed protective plate, the protective plate installed by the method according to the invention has better service life characteristics. In other words, it is possible to have a thinner coating that provides a significant improvement in test results with an acceptable service life. When the thickness of the protection plate is reduced from, for example, 1.8 mm to 0.6 mm, the sensitivity becomes 6d.
From B to an improved S / N ratio. For carrier members with one or more passage openings, it is possible to provide each opening with its own protective plate. The guard plates can be provided adjacent to each other in the region between the passage openings. Advantageously, the carrier member having a plurality of passage openings is connected to a single protection plate, which covers the mounting surface of the carrier member substantially completely and thus also of the carrier member. Cover all passage openings.

The surface area of the counter plate can exactly correspond to the area of the protection plate. It is preferred to use a counter plate with a somewhat smaller area and to position the counter plate in such a way that on all sides the protection plate projects slightly above the counter plate. This can be particularly advantageous if the soldering equipment of the carrier member, the guard plate and the counter member is to be fixed in the holding device before removal of the counter member from the solder layer holding the counter member. Prior to removal, in particular before polishing or grinding of the counter plate, this suitable holding in a sandwich manner is such that the holding device has its receiver which can fit the carrier member with the protection plate in a preferably gap-free manner. This is especially easy in the case. When the outer surface of the receiving body of the holding device is flush with the outer surface of the protective plate, the counter plate protrudes out of the holding device and can be removed by grinding in a geometrically defined manner. Precise removal can be assisted, especially if the holding device is hardened or hardened in the area surrounding the protective element to be inserted. The area in which the protective element is fitted can advantageously be made, for example, of a ceramic material. If the abrasive material is polished on a hard protective plate enclosure, the polishing of the counter plate is therefore slower or terminated.

The holding device is fitted in a wear shoe (sliding part) and is constituted in particular as a part of the wear shoe which, together with the secured protective element, protects the test probe mounted on said shoe. Is advantageous. Fabrication of the wear shoe can then be completed by the insertion of sandwich equipment, subsequent polishing of the counter plate and the solder layer holding the counter plate. Thus, each protection element is thus individually adapted to the dimensions of its fixed wear shoe. As a result of the fact that there is no substantial deflection of the guard, it is possible to move in a very precise manner from the inside of the test probe, ie from the side of the carrier member, to the guard. A typical interval is approximately 0 in this example.
It must be kept in mind that it is 1 mm and has an accuracy of 0.01 mm for the purpose of achieving precisely defined measurement conditions. These high-precision requirements shall be fulfilled, in particular, if a large number of test probes arranged together on the test probe circuit board, and thus cannot be individually adjusted, are to be moved together within precise intervals with respect to the guard plate. It must also be borne in mind that it can be fulfilled only in exceptional circumstances with difficult or possibly warped protective elements.

When the counter plate is removed and the soldered sandwich structure is installed in a holding device (especially a wear shoe), the protection element can in part be slightly loosened. However, the protective element made by the method of the invention can be placed on a holding device configured as a wear shoe and brought into contact with the test object.

Other features and details of the present invention can be gleaned from the following description of a preferred embodiment taken in conjunction with the drawings and the appended claims. Individual features, alone or in combination, can be implemented in embodiments. One embodiment of the present invention will now be described with reference to FIG. 1, which is a partial cross-sectional side view showing protection elements arranged on a test head having a stray flux probe.

[0026]

FIG. 1 is a side view showing a test head 1 partially in section. Close to the cross-section are three test tips 2, 3, 4 which receive the leakage flux emanating from a test object (not shown) arranged in contact with the lower side of the test head 1. The test probes 2, 3, and 4 are arranged in a spaced-apart manner on a common test probe circuit board 5 having a detector hole 6 through which a temperature detector 7 can penetrate, with a substantial tip 8 attached to the test probe 2. , 3, 4 are positioned at the same vertical height as the substantial tips 9, 10, 11.

The test probe circuit board 5 is held separated from the connection circuit board 13 by the spacer 12, and the connection circuit board is held by the screw 15 and the holding element 16 in the spacer 1.
2 is pressed by the cover 14 of the test head 1 as a test device. The test probe circuit board 5 is positioned on a wear shoe 17, which, like the cover 14, is made of glass fiber reinforced plastic. Circular probe paths 18, 19, 20 and a detector path 21 are formed in the wear shoe 17, and the test probes 2, 3, 4 and the temperature detector 7 pass through these detector paths. It can be inserted into the area below the wear shoe 17 together with the tip.

In the embodiment shown in FIG.
Are the substantial tips 9, 10, 11 of the test tips 2, 3, 4 are the passage openings 23 of the carrier member 26 of the protection element 22;
Wear shoes 17 in such a manner as to be inserted into 24, 25
It is fixed to. Passage openings 23, 2 in the downward direction
4 and 25 are completely covered with a protection plate 27 extending over the carrier member 26. Similarly, the detector passage opening 28 for the temperature detector 7 is covered.

In FIG. 1, on the side of the protective plate opposite to the carrier member 26, a counter plate 2 indicated by a broken line is shown.
9, the counter plate has the same thickness as the protection plate 27, beyond which the protection plate 27 protrudes in the region (boundary). Therefore, FIG.
9 shows the state of the test head before polishing.

Manufacture and Installation of the Protective Element First of all, the components of the protective element, namely the Remanit (trade name) protective plate 27 and the counter plate 29, as well as the Remanit (Remnit) in the illustrated embodiment,
The carrier member 26 manufactured by the above-described method is stacked in the arrangement shown in FIG. 1 and fixed in the soldering apparatus. If the individual elements expand to a range that fluctuates under combined heating as a result of the different coefficients of thermal expansion, this is done in such a way that the individual elements can move freely in a mutually parallel relationship to their contact surface Fixation occurs. The fixing of the individual elements to one another results from the retention of the individual elements in a generally central part. Following the brazing of the components at approximately 600 ° C. when the liquid solder material passes in an unassisted manner by capillary action between the individual components, the equipment is cooled and then removed from the soldering device after cooling. You.

The sandwich equipment formed by the carrier member 26, the protective plate 27 and the counter member 29 is then fitted into the opening of the test head 1 near the wear shoe 17, which is mounted below the wear shoe 17. The board 30 defines a lateral boundary. This sandwich equipment is attached to the wear shoe 17 and the ceramic plate 30 thereon with the aid of an epoxy adhesive. Due to its required accuracy in the positioning of the guard plate, said steps can be performed with special positioning devices. This ensures that only a small gap of approximately 0.1 mm exists between the substantial tip 9, 10, 11 of the test probe and the inside 31 of the protective plate. This spacing is to ensure that the sensitive tip of the test tip does not come into contact with the protection plate in the event of an impact on the protection plate and a corresponding bending of the protection plate into its corresponding passage opening. is necessary. For measurement reasons it is also necessary that the test tip be as close as possible to the protective plate. The dimension of the spacing between the protection plate 27 and the effective tips 9, 10, 11 of the test probe results in a compensated value which must be set correctly.

When the sandwich equipment is mounted at a precise spacing with respect to the test probe and the adhesive holding the sandwich equipment dries, the sandwich equipment is
That is, a portion of the counter plate 29 projecting beyond the lower side of the ceramic plate 30 can be removed by polishing. The hard ceramic plate 30 surrounding the sandwich equipment provides a suitable polishing boundary so that at the end of the polishing process the protective plate 2
The outer surface of 7 terminates on the outside and surface position of the ceramic plate 30.

[Brief description of the drawings]

FIG. 1 is a side view of a test head 1 partially sectioned.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Test head 2 Test probe 3 Test probe 4 Test probe 5 Test probe circuit board 6 Detector hole 7 Temperature detector 8 Effective chip 9 Effective chip 10 Effective chip 11 Effective chip 12 Spacer 13 Connection circuit board 14 Cover 15 Screw 16 Holding element 17 Wear shoe 18 Circular probe path 19 Circular probe path 20 Circular probe path 21 Detector circuit 22 Protective element 23 Passage opening 24 Passage opening 25 Passage opening 26 Carrier member 27 Protective plate 28 Detector Passage opening 29 Counter plate 30 Ceramic plate 31 Inside

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-200098 (JP, A) JP-A-3-204170 (JP, A) JP-A-2-96655 (JP, A) 44636 (JP, B2) JP 4-9000 (JP, B2)

Claims (13)

(57) [Claims] 1. The method according to claim 1, wherein the protective coating is provided on a carrier member.
6) A method of mounting on a protection element, in particular in such a way that at least one protection plate (27) is integrally connected with a mounting surface formed on a carrier member (26). In a method for producing (22),
A protection plate (27) is held between the installation surface and the counter member (29), and the carrier member (26) and the protection plate (27)
With the heating of the counter member (29), the carrier member (26) and the protection plate (27), and the protection plate (27) and the counter member (29) are simultaneously at least partially formed by one solder layer by a soldering process. Are joined together,
When the solder layer is crystallized, the counter member (2
9) and a method wherein the solder layer holding the same is removed from the protective plate (27). 2. A carrier member (26) and a protection plate (2).
7) and the counter plate (2)
2. The method according to claim 1, wherein the connection during 9) is performed by brazing silver hard solder. 3. The protective plate (27) is made of a wear-resistant material, in particular,
3. A method according to claim 1 or claim 2, wherein the method is made of a hard or hardened metal, preferably made of a hard metal or carbide. 4. The method according to claim 1, wherein the thermal expansion characteristics of the carrier member and the counter member are substantially identical to one another. The described method. 5. The method according to claim 1, wherein the carrier member and the counter member are made of the same material. 6. The method according to claim 1, wherein the counter element is configured as a plane-parallel counter plate. 7. The method according to claim 1, wherein the carrier member has at least one passage opening which can be completely completely covered by the protective plate. A method according to any one of the preceding claims. 8. The carrier member (26), the protective plate (27) and the counter member (2) before removing the counter member (29) and the solder layer holding the counter member.
Method according to any of the preceding claims, characterized in that the soldered version of (9) is fixed in a holding device (17). 9. The device according to claim 1, wherein the counter member and the solder layer holding the counter member are removed from the protective plate by polishing. the method of. 10. A protection device having the with the carrier member (26) at least one protection plate integrally structurally connected to the carrier member (26) to (27), substantially planar carrier member (26) A protective plate (27), at least partially parallel to the plane, is soldered, in particular with hard solder, the surface of the protective plate (27) in the outer region remote from the carrier member (26) being a counter member (27). 29) A protective element characterized in that the surface is formed by removing the solder layer together with the solder layer, for example, by polishing. 11. The protection device (22) includes a holding device (17,
30) and at least one test tip (2,
3, 4) are protected, and the stylet is
11. The protection according to claim 10, wherein the stylus flux probe is movable relative to the test object in its working area, and the protection element has a contact surface for contacting the test object. element. 12. The protective plate (27) is made of a wear-resistant material, in particular hard or hardened metal, preferably made of hard metal or carbide. A protection element according to claim 11. 13. The carrier member (26) has at least one passage opening (23, 24, 25) completely covered by a protective plate (27). 13. The protection device according to any one of the above items 12.