WO2020038817A1

WO2020038817A1 - Method for determining the quality of a welded or soldered connection when producing saw blades

Info

Publication number: WO2020038817A1
Application number: PCT/EP2019/071905
Authority: WO
Inventors: Marcel Credé; Udo Netzelmann
Original assignee: Credé Vermoegensverwaltungs-Gmbh + Co. Kg; Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V.
Priority date: 2018-08-20
Filing date: 2019-08-15
Publication date: 2020-02-27
Also published as: DE102018120241A1; DE102018120241B4

Abstract

The invention relates to a method for determining the quality of a welded or soldered connection (4) when welding or soldering hard material bodies (6) to teeth (8) of a saw blade (10), in particular of a band saw blade or a circular saw blade, by means of welding, in particular resistance welding, or soldering, wherein each tooth (8) and a respective hard material body (6) are joined together. According to the invention, after welding or soldering the hard material body (6) to the tooth (8) by a heat-introducing device (12), a heat quantity Q is introduced into the hard material body (6), and a temperature is detected by means of a temperature-detecting device (18). The quality of the welded or soldered connection (4) is determined by means of an electronic data processing device (22) using the detected temperature.

Description

Title: Method for determining the quality of a welded or soldered joint in the manufacture of saw blades

description

The invention relates to a method for determining the quality of a welded or soldered connection when welding or soldering hard material bodies on teeth of a saw blade, in particular a band or circular saw blade

Welding, in particular resistance welding or soldering, a respective tooth and a respective one

Hard material bodies are joined together.

The invention further relates to a device for

Performing the procedure and a Resistance welding device with a welding electrode for welding a respective hard material body to a respective tooth of the saw blade.

When manufacturing saw blades, for example, electrically weldable hard material bodies are attached to one

Weld on the teeth of the saw blades

Resistance welding is created by melting the welded objects at the welding point by supplying energy and typically welding them under the action of a contact pressure by solidifying the melt.

If a hard material body is mentioned above, a body of any geometry, in particular a sphere, cylinder or plate shape, is made from it

Hard material, in particular hard metal, cermet, cutting ceramic, diamond, in particular coated, understood. at

Tungsten carbide can be, for example

act weldable sintered material with a grain size of 0.2 gm - 1.2 gm, in particular consisting of 6% to 16% binder, mostly cobalt (Co), and a corresponding remainder 94% to 84% in particular tungsten carbide (WC), especially with small amounts of tantalum (Ta), niobium (Nb), or carbides, such as tantalum carbide (TaC), titanium carbide (TiC), niobium carbide (NbC). As a binder, in addition to cobalt

in particular nickel (Ni) or iron-cobalt-nickel alloys (FeCoNi) come into question. To improve the cutting and / or sliding properties, the hard metal can be coated with TiC, TiN, titanium carbonitride (TiCN) or include aluminum oxide (A1 ₂ 0 ₃₎ . At Cermet and

Cutting ceramics are, for example, weldable sintered materials with no or only a small proportion of tungsten carbide; Mixed carbides, such as titanium carbide or titanium nitride or mixtures thereof, are customary here. The binders mentioned above can be used as binders.

Process fluctuations, geometrical deviations, wear and tear on welding or soldering tools and other influences can occasionally lead to defective welding or

Lead solder connections. Typical defects in welding are, for example, the under-weld, in which only a small area of the weld provides a bond, or so-called "adhesives", which are optical

good-looking welded joints, which, however, cannot mechanically transmit any significant forces. Under-welding and glue are caused, for example, by cracks, voids, binding errors or insufficient ones

Welding through the welded joint or the

welding components. Another typical deficiency is overwelding, due to shape or dimensional deviations, especially with the formation of a

Bead, too large a proportion of area provides a bond. Typical defects in soldered connections are, for example, cold solder joints or the use of too much solder, which in turn can lead to shape or dimensional deviations, in particular with the formation of a bead, so that an excessively large proportion of the area provides a bond. Such shortcomings can be used in the later use of the saw blade

Malfunctions, for example disconnection of the

Hard body from the teeth, lead.

In order to test the quality of welded or soldered connections in the case of saw blades, there are destructive test methods from the prior art, for example the metallographic one

Preparation known, with random samples

Saw blades are removed and the quality is assessed on the basis of micrographs of the welded or soldered connection. The disadvantage of this is, for example, that

Incompleteness of the test and the loss of the tested saw blades.

It is also known from the prior art that

Quality of the welded or soldered connection based on the

to determine the electrical contact resistance between the hard material body and the saw blade. For this purpose, an electrical current is passed over the welding or soldering point and the voltage drop at the joining partners is determined as a test variable. To do this, it is necessary to make electrical contact with the test object at four points. The additional contact resistances occurring here can in turn

Falsify measurement.

Further non-destructive test methods known from the prior art for determining the quality of welded or soldered connections have been proven for the application

Saw blades are unsuitable. For example, the

Visual inspection only superficial and therefore imprecise. The Ultrasonic testing is not suitable due to the small size and the sometimes complex shapes of the hard material bodies. The geometry of the saw blade and magnetism of the materials make eddy current testing difficult. The

On the one hand, X-ray inspection is time-consuming and therefore too slow to be used in a

Series production, on the other hand, the X-rays can hardly penetrate the hard material bodies.

The invention is therefore based on the object

Specify a method for determining the quality of a weld or solder seam, with which the disadvantages of the methods known from the prior art can be overcome.

It is proposed according to the invention that after welding or soldering the hard material body to the tooth by means of a heat introduction device, a quantity of heat Q in the

Hard material body is introduced, and that a temperature is detected by means of a temperature detection device, and the quality of the welded or soldered connection is determined on the basis of the detected temperature by means of an electronic data processing device.

When the quantity of heat Q is introduced into the hard body, part of the quantity of heat Q flows into the saw blade via the welded or soldered connection. So it hardens both the hard material body and that

Saw blade, the heat distribution from the

The heat dissipation capacity of the welded or soldered connection is dependent. The temperature is recorded and with a Reference temperature compared, with the quality of the welded or soldered connection being deduced from the deviation of the detected temperature from the reference temperature. According to the invention, the quality of the welded or soldered connection is determined via the heat dissipation capacity of the welded or soldered connection. Comparing the

Temperature with the reference temperature

for example comparing absolute

Temperature values, temperature profiles and rates of change. The reference temperature is in particular that

Temperature, which is good at a welding or

Soldered connection results, whereby a good welded or soldered connection means a welded or soldered connection which fulfills quality requirements, in particular with regard to strength.

In this way it is possible to determine the quality of the welded or soldered connection in the case of saw blades during the manufacture of the saw blades.

In the method according to the invention

assumed that a certain proportion of those in the

The amount of heat introduced into the hard material body is transferred to the saw blade via the weld or solder connection. If there is a binding defect, for example in the form of an adhesive or a weld or a cold soldering point, the heat is dissipated more slowly via the welded or soldered connection compared to the heat dissipation with a good welded or soldered connection. In this case, the saw blade heats up more slowly and the hard material body warms up faster. On the other hand, if there is overwelding, for example, the heat will dissipate faster

Weld joint derived compared to

Heat dissipation with a good weld connection. In this case, the saw blade heats up faster and the hard material body heats up more slowly. By detecting the temperature, it is therefore possible to draw conclusions about the heat dissipation capacity of the welded or soldered connection and thus the quality of the welded or soldered connection.

In principle, it is conceivable that the temperature at

Saw blade is captured. Advantageously, the

Temperature recorded at the tooth of the saw blade to which the hard body in question is attached by means of the welded or soldered connection.

In contrast, it can also prove to be advantageous for the temperature to be recorded on the hard material body. Due to the strong warming during the

Welding or soldering can in the worst case

Changes on the surface of the saw blade,

in particular so-called tarnishing colors occur that change the emissivity of the saw blade. By detecting the temperature on the hard material body, it can thus advantageously be avoided that the detected temperature is influenced by the changed emissivities of the saw blade, which is particularly important when measuring the temperature by means of infrared radiation. It can advantageously be provided that the amount of heat Q is introduced into the hard material body on a first side with respect to a plane of the saw blade and the temperature on the hard material body is recorded on a second side of the hard material body opposite the first. In this case, the hard material body is heated on one side and the temperature is recorded on the other side, in each case with respect to the plane of the saw blade.

In principle, the temperature can be recorded in any way per se. The temperature is preferably measured without contact, in particular by means of an infrared single detector with infrared optics.

The temperature is advantageously determined by means of a

Infrared camera recorded as a temperature detection device. The temperature can be measured using thermography

in particular over an area B. Surface B can be a surface section with

act arbitrarily definable dimensions. The area B is preferably not too large, it can be 0.5 to 10 mm ² .

The introduction of the amount of heat Q into the

Hard material body done in any way per se.

The amount of heat Q is preferably introduced into the hard material body without contact. For example, the respective hard material body can be heated by means of inductive excitation. It can advantageously be provided that the amount of heat Q is in the form of a laser power Pulse with pulse duration t _{p is introduced} into the hard material body.

The pulse duration t _p is advantageously from 0.05 s to 0.5 s. The pulse duration is approximately in the order of magnitude of the thermal diffusion time through the hard material body or through the welded or soldered connection.

The temperature is advantageously recorded over a period of time t _mess . The time period t _mess is in particular 0.1s to 3s. The temperature or the course of the over the

Time duration t measured temperature can then be compared with a reference temperature or a reference temperature _curve . It is also conceivable that an averaged temperature change rate of the temperature recorded over the time period t _{meas is} determined and compared with an averaged reference change rate. Furthermore, it is also conceivable that a maximum

Temperature change rate is determined and compared with a maximum reference change rate.

It is conceivable that the temperature is only recorded after the quantity of heat Q has been introduced into the hard material body.

In contrast, it has proven to be advantageous that the temperature is recorded at least partially during the introduction of the amount of heat Q into the hard material body. The temperature can therefore be detected from the start of the introduction of the amount of heat by means of the laser pulse with the pulse duration t _p on. In particular, the time period t _me ss is longer than the time period t _p . The pure time to determine the The quality of a welded or soldered connection from the introduction of the amount of heat is in particular 0.1s to 5s, in particular 0.1s - 3s.

In further development of this inventive idea can in

It can advantageously be provided that a time-averaged rate of change of the temperature ATp, _{ge is} determined during the introduction of the amount of heat Q into the hard material body, that a time-averaged temperature Tmess, averaged over the time period t _mess , and that a normalized temperature change rate hT _normie rt is determined by the averaged rate of change

DTr, averaged by the averaged temperature T _{mess, is} averaged divided. So it becomes the time averaged

Rate of change of temperature ATp, _ge mitteit during the

Introducing the amount of heat Q, that is during the time period t _p, is determined, wherein HTP, _ge mitteit is determined for example according to the following formula:

DTr, averaged

The rate of change HTP, _ge can mitteit t _p, or are determined over a time period to the entire period of time, preferably 0 <to <t _p.

Furthermore, the time-averaged temperature T _{mess is determined,} averaged over the time period t _mess , where T _mess, averaged

is determined using the following formula, for example:

T mess, averaged

The rate of change AT Division _P, _Ge mitteit by T _{mess averaged} results in the normalized rate of temperature change AT _{normalized /} AT being then _normalized for example by the following formula is illustrated:

ft r _ DTr, averaged

1 standardized— ^~ ·

1 meas, averaged

The quality of the welded or soldered connection is then determined on the basis of the standardized temperature change rate _{hT normie} rt r, in which the standardized temperature change rate hT _normalizes with a standardized one

Reference temperature change rate AT _re f, normalized is compared, the normalized reference temperature change rate

AT _re f, normalizes the normalized rate of change of a good one

Reference weld or reference solder joint is. The normalized temperature change rate AT _normalized is time-related and independent of the laser power and of disturbances, such as changes in emissivity.

The invention further relates to a device for carrying out the method comprising a

Heat introduction device for introducing a quantity of heat Q into the hard body after welding or soldering the hard body to the tooth, a

Temperature detection device for detecting the temperature and an electronic data processing device for determining the quality of the welded or soldered connection of the tooth and hard material body on the basis of the detected temperature.

In principle, the heat introduction device can be used in any way, for example as an inductive one Heat introduction device, be formed.

The heat introduction device is advantageously a laser.

The temperature detection device can also be used in any way, for example as

Infrared single detector with infrared optics, be formed. The temperature detection device is preferably an infrared camera.

It can advantageously be provided that the

Heat introduction device and the

Temperature detection device are arranged and designed such that the amount of heat Q on a first side with respect to a plane of the saw blade in the

Hard material body can be introduced, and that the temperature on the hard material body on one of the first opposite second side of the hard material body can be detected.

The invention also relates to a

Resistance welding device with a welding electrode for welding a respective hard material body to a respective tooth of the saw blade, the respective

Hard material body and the respective tooth of the saw blade are melted on or melted on by introducing a welding pulse and joined together, comprising a device according to one of claims 11 to 14.

Further advantages, features and details of the invention emerge from the subclaims and from following description, in which a preferred embodiment is described in detail with reference to the drawing. You can do that in the drawing

Features shown and mentioned in the claims and in the description individually individually or in

any combination be essential to the invention. The drawing shows:

Fig. 1 is a schematic view of the invention

Set up from above with saw blade;

FIG. 2 shows a schematic oblique view of the saw blade from FIG. 1;

Fig. 3 is a schematic view of an inventive

Resistance welding device from above with

Saw blade;

4 shows a schematic course of a pulse;

Fig. 5 curves of a recorded on a saw blade

Temperature;

Fig. 6 shows a course of a recorded on a saw blade

Temperature, and

7 shows the rate of change of the temperature profile

Figure 6. FIG. 1 shows a schematic view of the invention according to the invention, designated overall by reference number 2

Device for determining the quality of a welded or soldered joint 4 when welding or soldering

Hard material bodies 6 on teeth 8 of a saw blade 10. In the figures, weld connections 4 between tooth 8 and hard material body 6 are shown by way of example. However, the invention is also applicable to soldered connections. The schematic section of the saw blade 10 from FIG. 1 is shown in an oblique view in FIG. In the illustrated

In one embodiment, a hard material body 6 is already welded to the tooth 8 of the saw blade 10, so that a weld connection 4 is formed between the hard material body 6 and the tooth 8 of the saw blade 10.

The device 2 comprises a heat introduction device 12 for introducing a quantity of heat Q into the hard material body 6. The heat introduction device 12 is, for example, a laser. The amount of heat Q is in this case in the form of a laser pulse P with the pulse duration t _p in

Hard material body 6 initiated. FIG. 4 shows an example of a time profile 14 of the laser pulse P.

According to the illustrated embodiment, the

Heat introduction device 12 arranged and designed such that a quantity of heat Q on a first side 16 of the hard material body 6 into the hard material body 6

is initiated. When the amount of heat is introduced into the hard material body 6, it heats up and part of it The amount of heat introduced is dissipated via the welded joint 4 into the tooth 8 of the saw blade 10.

The device 2 further comprises a

Temperature detection device 18 for detecting a temperature. The temperature detection device 18 is, for example, an infrared camera.

According to the illustrated embodiment, the

Temperature detection device 18 arranged and designed such that the temperature on a second side 20 of the

Hard material body 6 is detected.

In principle, however, others are also not shown

Embodiments are conceivable in which the temperature is detected, for example, on the first side 16 of the hard material body 6, on which the amount of heat is also introduced, or on the tooth 8 of the saw blade 10.

The device 2 further comprises an electronic one

Data processing device 22. The of the

Temperature detection device 18 detected temperature is transmitted to the electronic data processing device 22 via a communication link 24. The

Electronic data processing device 22 determines the quality of the data based on the detected temperature

Welded joint 4 by comparing the detected temperature with a reference temperature, and the

Deviation of the recorded temperature from the

Reference temperature is determined. This is in a wide range To understand meaning and records the comparison of individual temperature values or temperature profiles.

In the method according to the invention

assumed that a certain proportion of those in the

Hard material body 6 introduced amount of heat over the

Welded connection 4 is transferred to the saw blade 10. This heats both the saw blade 10 and the hard material body 6, the heating of which

Heat dissipation capacity of the weld joint 4 is dependent.

If, for example, there is a binding defect or insufficient weld-through, the heat is dissipated more slowly via the welded connection 4 compared to

Heat dissipation with a good weld connection 4. In this case, the saw blade 10 heats up more slowly and the hard material body 6 heats up more quickly. A temperature profile T _mess , i, which is recorded on the hard material body as an example in this case, is shown in FIG. 5 by curve 26. The temperature profile T _mess , i is above the reference temperature profile T _ref also shown in FIG. 5 in the case of a good welded joint 4.

On the other hand, there is an overwelding in the form of a

Shape deviation with formation of a bead before, the heat is dissipated faster via the weld 4 compared to the heat dissipation with a good one

Welded joint. In this case, it warms up Saw blade 10 thus faster and the hard material body 6 heats up more slowly. A temperature profile T _mess , 2, which is recorded on the hard material body 6 as an example in this case, is represented by curve 30 in FIG. The curve T _ess , 2 is below the reference _temperature curve T _ref . The quality of the welded joint 4 can then be inferred from the deviations of the courses T _{mess, i} and T _mess , 2 from the course of T _ref .

Furthermore, the electronic data processing device 22 is in particular designed to be a standardized one

Determine the rate of temperature change AT _standardized . This is explained below with reference to FIGS. 6 and 7. FIG. 6 shows a temperature profile recorded on the hard material body. The temperature curve corresponds, for example, to one of the curves T _{mess, i} or T _mess , 2 from FIG. 5, the

Temperature curve by subtracting the value To

was postponed. By subtracting with mean values of temperature, the measured values recorded can

existing temperature fluctuations can be compensated. Based on the temperature curve shown in Fig. 6, a time-averaged is now according to the following formula

Temperature T _mess, averaged over time t _meas :

T mess, averaged— -ü j'- rteWt.

tmess t U

Figure 7 shows the rate of change of the temperature curve of Figure 6. On the basis of the rate of change shown in Fig. 7 in accordance with the following formula will be a time-averaged rate of change AT _p, _gem itteit the detected temperature T _p during the introduction of the amount of heat Q into the hard material body 6, that is to say during the time period t _p :

DT _R , averaged

According to the illustrated embodiment, the

Rate of change AT _P, _Ge mitteit over the period of time to

determined, where 0 <to <t _p .

The normalized rate of temperature change AT _Normier t is then calculated by the average rate of change AT _P, _Ge mitteit is divided averaged by the average temperature T _measured:

DT _r , averaged

ATnormiert-

Tmess, averaged

The quality of the welded joint 4 is then determined in particular by comparing the normalized rate of change AT _normalized t with a normalized reference _temperature rate of change AT _re t, the normalized

Reference _temperature change rate AT _ret , _{normalized is} the normalized rate of change of a good reference _{welded joint} .

Finally, FIG. 3 shows a schematic illustration of a resistance welding device 32 with a saw blade 10. The resistance welding device 32 comprises a welding electrode 34 for welding a respective one

Hard material body 6 to a respective tooth 8 of the

Saw blade 10, the respective hard material body 6 and the respective tooth 8 of the saw blade 10 being melted or melted on by introducing a welding pulse and

be joined together. After the welding process has ended, the saw blade 10 is moved in a feed direction 38 by means of a saw blade feed device 36, so that another

Hard material body 6 to a subsequent tooth 8

can be welded. The saw blade feed device 36 comprises, for example, gripping or clamping devices for gripping the saw blade 10, which are mounted on feed carriages. The feed carriage can be moved, for example, by means of a drive, in particular an electric linear drive, in the direction of the double arrow 40 parallel to the feed direction 38. Resistor device 32 also includes device 2

Heat introduction device 12,

Temperature detection device 18 and electronic

Data processing device 22. By moving the

Saw blade in the feed direction 38, the tooth 8, to which a hard material body 6 is already welded, is brought into a region between the heat introduction device 12 and the temperature detection device 18, so that the device 2 after the respective one has been welded on

Hard material body 6 to the tooth 8 the quality of

respective weld 4 of tooth 8 and

Hard material body 6 can be determined. It can

in particular and preferably all welded connections in a saw blade immediately after their manufacture in the manner according to the invention with regard to the quality of the

Welded connection to be checked.

Claims

claims

1. Procedure for determining the quality of a sweat

or solder connection (4) when welding or soldering hard material bodies (6) to teeth (8) of a saw blade (10), in particular a band or circular saw blade, by welding, in particular resistance welding, or soldering, a respective tooth (8) and a respective hard material body (6) are joined together, characterized in that after welding or soldering the hard material body (6) to the tooth (8) by means of a heat introduction device (12), a quantity of heat Q is introduced into the hard material body (6), and that by means of a

Temperature detection device (18) a temperature is detected, and based on the detected temperature by means of an electronic

Data processing device (22) the quality of the welded or soldered connection (4) is determined.

2. The method according to claim 1, characterized in that the temperature on the tooth (8) of the saw blade (10) is detected.

3. The method according to claim 1, characterized in that the temperature on the hard material body (6) is detected.

4. The method according to claim 3, characterized in that the amount of heat Q on a first side (16) with respect to a plane of the saw blade (10) in the

Hard material body (6) is initiated and the

Temperature on the hard material body (6) is detected on a second side (20) of the hard material body (6) opposite the first side (16).

5. The method according to any one of claims 1 to 4, characterized in that the temperature is detected by means of an infrared camera as a temperature detection device (18).

6. The method according to any one of the preceding claims, characterized in that the amount of heat Q by means of laser power P (t) in the form of a pulse (14)

Pulse duration t _{p is introduced} into the hard material body.

7. The method according to claim 6, characterized in that the pulse duration t _{p is} 0.05 s to 0.5 s.

8. The method according to any one of the preceding claims, characterized in that the temperature is detected over a period of time t _mess .

9. The method according to claim 8, characterized in that the temperature is detected at least partially during the introduction of the amount of heat Q into the hard material body (6).

10. The method according to one or more of the preceding claims, characterized in that a time-averaged rate of change of the temperature AT _p , _{according to} the introduction of the amount of heat Q in the Hard material body (6) is determined that a time-averaged temperature T _mess, averaged during the

Period of time t _measured is determined, and in that a normalized temperature change rate hT _Normie rt is determined by the average rate of change AT _P, _Ge mitteit by the average temperature T _measured, is divided averaged.

11. Device (2) for performing the method according to one or more of the preceding claims, characterized in that the device (2) is a heat introduction device (12) for introducing a quantity of heat Q into the hard material body (6) according to the

Welding or soldering the hard material body (6) to the tooth (8), a temperature detection device (18) for detecting the temperature and an electronic data processing device (22) for determining the quality of the welded or soldered connection (4) of tooth (8) and hard material body (8) based on the recorded

Temperature includes.

12. Device (2) according to claim 11, characterized

characterized in that the heat introduction device (12) is a laser.

13. Device (2) according to claim 11 or 12, characterized

characterized that the

Temperature detection device (18)

Is infrared camera.

14. Device (2) according to one of claims 11 to 13, characterized in that the Heat introduction device (12) and the

Temperature detection device (18) are arranged and designed in such a way that the amount of heat Q can be introduced into the hard material body (6) on a first side (16) with respect to a plane of the saw blade (8), and that the temperature at the hard material body (6) is on a the second side (20) of the hard material body (6) opposite the first side (16) can be detected.

15. Resistance welding device (32) with a

Welding electrode (34) for welding a respective one

Hard material body (6) on a respective tooth (8) of a saw blade (10), the respective

Hard material body (6) and the respective tooth (8) of the saw blade (10) are melted on or melted on by introducing a welding pulse, and are joined together, characterized in that the

Resistance device (32) comprises a device (2) according to one of Claims 11 to 14.