DE102007007901A1 - Method for determining the susceptibility of a metal sheet to hot cracks comprises preparing a testing body made from a metal sheet, clamping along a first edge, forming a welding strip along a path and further processing - Google Patents

Abstract

Method for determining the susceptibility of a metal sheet to hot cracks comprises preparing a testing body (1) made from a metal sheet, clamping along a first edge (K1), forming a welding strip (3) along a path running skew to the edges (K1, K2) through the testing body at an angle of 0-60[deg] and determining the length of a hot crack (6) formed in the welding strip as a measure for hot crack susceptibility. An independent claim is also included for a testing body used in the above method.

Description

The The invention relates to a method for determining the hot-crack susceptibility a sheet.

According to the state of the art is from the dissertation of Rolf Michael Hilbinger, "Hot cracking when welding aluminum in sheet edge position", University of Bayreuth, 2000 , a method for determining the hot crack susceptibility of a sheet with the following steps:
Providing a rectangular test body made of the sheet, having a first and a second long edge,
Clamping the test specimen along the first long edge,
Producing a weld band in a direction parallel to the first long edge, and
Determining a length of a hot crack forming in the sweatband from the outer circumference of the test piece inwards as a measure of the hot crack susceptibility.

To the known method is the distance of the weld band of the free long edge varies. Finally, the distance is determined in which no hot cracks are observable for the first time. This Distance serves as a measure of the susceptibility to cracking of the material. According to the known method, it is disadvantageous required, to determine the hot crack susceptibility a variety of To examine samples. Especially if there are no indications for the hot-crack susceptibility of the material, a large distance range must be investigated become. That increases the number of required test specimens considerably.

According to the prior art is further from the DE 100 51 061 C2 a method is known in which for hot crack testing of material combinations a test specimen made of two different materials is clamped on both sides. As a measure of the hot crack susceptibility, the length of a crack is measured, which forms in a weld seam connecting the two materials. To compensate for thermal expansion, the joined workpieces also have a tongue and groove connection. The preparation of the test piece according to the known method is complicated.

The US 4,763,521 describes another method for determining the hot crack susceptibility of sheets. In this case, a provided with a sweatband test body is clamped on both sides of the weld band in a jig. The tensioning device creates a tension across the sweatband. The known method disadvantageously requires a high expenditure on equipment.

task The invention is to the disadvantages of the prior art remove. It is intended in particular a method for determining the hot crack susceptibility a sheet are given, which quickly and without much equipment feasible is.

These The object is solved by the features of claims 1 and 9. Advantageous embodiments The invention will become apparent from the features of claims 2 to 8th.

• a) Bereitstellen eines aus dem Blech hergestellten rechteckigen, eine erste und eine zweite lange Kante aufweisenden Prüfkörpers,
• b) Einspannen des Prüfkörpers entlang der ersten langen Kante,
• c) Herstellen eines Schweißbands entlang eines schräg bezüglich der langen Kanten durch den Prüfkörper unter einem Winkel α von mehr als 0° und weniger als 60° laufenden Wegs, welcher sich von einer in der Nähe einer im Bereich der zweiten langen Kante befindlichen Ecke in Richtung zur gegenüberliegenden kurzen und/oder ersten langen Kante erstreckt, und
• d) Bestimmung einer Länge eines im Schweißband sich ausbildenden Heissrisses als Maß der Heissrissanfälligkeit.

According to the invention, the following steps are provided in a method for determining the hot crack susceptibility of a sheet metal:

• a) providing a rectangular body made of sheet metal, having a first and a second long edge,
• b) clamping the test specimen along the first long edge,
• c) producing a weld band along a path obliquely with respect to the long edges through the test specimen at an angle α of more than 0 ° and less than 60 °, which extends from one in the vicinity of a corner located in the region of the second long edge in the direction extends to the opposite short and / or first long edge, and
• d) Determining a length of a hot crack forming in the sweatband as a measure of the hot-crack susceptibility.

at The proposed method is a method with a self-loaded test specimen. It only one clamping along a first edge of the specimen is required. In particular, can be an expenditure on equipment for the production of Tensions across the weld are omitted become. The proposed method can be made using rectangular and thus particularly easy to produce test specimen can be performed. Furthermore, it is possible with the proposed method, the Hot cracking susceptibility using fewer samples. The proposed Process is particularly cost-effective and effectively feasible.

To an advantageous embodiment of the test specimen is only along the first long edge clamped. Experiments have shown that one only one-sided clamping of the test piece along the first long Edge for the quantitative determination of hot crack susceptibility is sufficient. The proposed method can with a small equipment expenditure are performed.

According to a further embodiment, it is provided that as a measure of the hot crack susceptibility, the length of a weld in the outer Um fang of the specimen is used inwardly forming hot crack. As an alternative to the length of the hot crack, a measure of the hot crack susceptibility may alternatively be determined as the distance of the weld band from the second long edge, in which no hot crack in the sweatband occurs at all. Of course, it is also possible to use both the length of an observed hot crack and the distance of the crack end of the second long edge to determine the hot crack susceptibility.

To In a further embodiment, the test specimen has a thickness in the range from 0.6 to 5.0 mm. A length The long edge can range from 15 to 25 cm, preferably 20 cm, a length of short edge in the range of 5 to 15 cm, preferably 10 cm. The proposed geometry of the test specimen allows a determination of the hot crack susceptibility with a very good reproducibility.

To a particularly advantageous embodiment is an angle α as an angle between 20 ° and 50 °, preferably between 40 ° and 48 °, especially preferably of 45 °, selected. An angle α in the aforementioned Range has the advantage that with a suitable size of the specimen the hot crack susceptibility often already determined with a single specimen can be. When using small angles for α, for example, angles in the range between 10 ° and 25 °, will a greater length of the hot crack observed as using larger angles of, for example 25 ° to 45 °. at unknown hot crack susceptibility It is thus possible, first with a big one Angle α of for example, 45 ° coarse to investigate, up to which distance the hot crack against the second long edge runs. In a subsequent further attempt can then to increase the Accuracy of determination of hot crack susceptibility a suitable minor Angle α can be chosen especially by the distance of the crack end from the second long edge to be determined exactly.

The Production of, preferably straight, sweatband can either starting from the corner or ending at the corner become. The production of the sweatband can be both with and without the introduction of a welding filler respectively. The production of the weld band can advantageously done with a laser.

To further requirement The invention is a test specimen manufactured according to the inventive method intended. Such a test piece can for example, for evidence purposes. Furthermore, at archiving a specimen observed whether the hot crack changes its length over time.

following Be exemplary embodiments of Invention explained in more detail with reference to the drawings. Show it:

1 a schematic representation of a test body according to the invention and

2a -C photographs of specimens with different welding angles α.

In 1 is a rectangular, made of sheet metal test specimen 1 at its first long edge K1 clamping in a restraint 2 fixed. An opposite second long edge is designated by the reference K2. From one located in the region of the second long edge K2 corner E runs with the reference numeral 3 designated sweatband at a welding angle α with respect to the second long edge K2 from the area of the corner E in a substantially diagonal direction in the test specimen 1 until near a first short edge K3. A welding direction extends from the corner E in the direction of the first short edge K3 and is indicated by the arrow P. The reference numerals 4 and 5 denote the solidus as well as the liquidusher of the sweatband 3 , One to the outer circumference of the specimen 1 at the second short edge K4 opening hot crack 6 ends at one with the reference numeral 7 designated crack end, which has a distance A from the second long edge K2.

The hot crack 6 is due to thermally induced stresses in the specimen 1 generated, which are caused by the welding. The location of the crack end 7 hangs at comparable geometry of the specimen 1 of its material properties.

The 2a -C show the dependence of a length L of the hot crack 6 depending on the welding angle α. It can be clearly seen that as the welding angle α increases, the length L of the hot crack 6 decreases. Taking advantage of this effect can at unknown hot crack susceptibility first with a large welding angle α, for example, 40 ° to 50 °, the approximate length L of the hot crack 6 or whose distance A from the second long edge K2 be estimated. A refined determination of the hot crack susceptibility can subsequently be made in a second experiment, in which the welding angle α is chosen smaller as a function of the result of the first test and thus the hot crack susceptibility of the test specimen 1 can be determined more precisely.

1

specimen

2

clamping

3

sweatband

4

Solidustherme

5

Liquidustherme

6

hot crack

7

crack end

K1

first long edge

K2

second long edge

K3

first short edge

K4

second short edge

e

corner

P

welding direction

L

crack length

Claims (9)

Method for determining the hot crack susceptibility of a sheet, comprising the following steps: a) providing a rectangular test body made of sheet metal, having first and second long edges ( 1 ), b) clamping the test specimen ( 1 ) along the first long edge (K1), c) producing a sweatband ( 3 ) along an oblique with respect to the long edges (K1, K2) through the test body ( 1 ) at an angle α greater than 0 ° and less than 60 °, extending from a corner (E) near a second long edge (K2) in the direction of the opposite short (K3) and / or or first long edge (K1), and d) determining a length (L) of one in the sweatband ( 3 ) forming hot crack ( 6 ) as a measure of hot crack susceptibility. Process according to claim 1, wherein the test body ( 1 ) is clamped only along the first long edge (K1). Method according to one of the preceding claims, wherein in step lit. b) as a measure of the hot-crack susceptibility, a length (L) of one in the sweatband ( 3 ) from the outer circumference of the test specimen ( 1 ) inwardly forming hot crack ( 6 ) is used. Method according to one of the preceding claims, wherein the test body ( 1 ) has a thickness in the range of 0.6 to 5.0 mm. Method according to one of the preceding claims, wherein as angle α Angle between 20 ° and 50 °, preferably between 40 ° and 48 °, is selected. Method according to one of the preceding claims, wherein the production of the welding band ( 3 ) starting from the corner (E) or ending at the corner (E). Method according to one of the preceding claims, wherein the production of the welding band ( 3 ) without welding filler material. Method according to one of the preceding claims, wherein the production of the welding band ( 3 ) by means of laser. Test specimen, manufactured according to the method of any one of the preceding claims.