ADJUSTABLE SHIELD FOR LOCAL AUSTENITIZING

Abstract

A shield covers a predetermined region of a plate workpiece during tempering of the plate workpiece in a furnace in which the shield and the workpiece are subjected to an austenitization temperature while the predetermined region of the plate is shielded by the shield against heat. The shield has at least one first shield part shaped to cover at least some of the predetermined region of the workpiece, at least one second shield part, and a fastener or the like securing the second part movably relative to or removable from the first part such that the first and second parts together achieve an optimum shape fully covering and shielding the predetermined region of the plate workpiece.

Claims

1. A shield for covering a predetermined region of a plate workpiece during tempering of the plate workpiece in a furnace in which the shield and the workpiece are subjected to an austenitization temperature while the predetermined region of the plate is shielded by the shield against heat, the shield comprising: at least one first shield part shaped to cover at least some of the predetermined region of the workpiece; at least one second shield part; and means securing the second part movable relative to or removable from the first part such that the first and second parts together achieve an optimum shape fully covering and shielding the predetermined region of the plate workpiece.

2. The shield according to claim 1, wherein the second shield part and/or a third shield part can be adjusted or aligned on the first part.

3. The shield according to claim 1, wherein the means is a spindle engaged operatively between the first and second shield parts.

4. The shield according to claim 3, wherein the spindle is provided with a handle or hand wheel for rotation.

5. The shield according to claim 3, wherein the means includes an electric servomotor connected to the spindle.

5. The shield according to claim 1, wherein there are two such first parts between which the workpiece is sandwiched and two respective second parts.

6. The shield according to claim 5, wherein the first parts are congruent to each other and the second parts are also congruent to each other.

7. The shield according to claim 1, wherein the shield lies in a plane and the first parts has an outer edge turned toward an outer edge of the second part, the outer edge of the first part having a lip extending parallel to the plane toward the second part, the outer edge of the second part having a respective lip projecting parallel to the plane the outer edge of the first part, the lips overlapping such that radiant energy transverse to the plane is blocked from going through the shield where the lips overlap, the means serving to adjust a position of the second part relative to the first part by movement parallel to the plane.

8. The shield according to claim 7, wherein the lips are formed by strip secured to the respective parts.

9. The shield according to claim 7, wherein the lips are unitary with the respective parts.

10. A method of locally tempering a plate workpiece comprising the steps of: providing a first part and a second part that together form a shield for a predetermined region of a plate workpiece; adjusting the relative positions of the first and second part or a size or shape of the second part such that the first and second parts only covers a predetermined region of the workpiece; covering the predetermined region of the workpiece with the shield while leaving the rest of the workpiece exposed; heating the workpiece with the shield covering the predetermined region in a furnace such that the workpiece is only heated to the austenitizing temperature where it is not covered by the shield; and subsequently cooling the workpiece such that it has high-strength areas and areas corresponding to the predetermined region of a lower strength.

11. The method of claim 10, wherein the relative positions of the first and second part are adjusted inside the furnace.

12. The method of claim 10, wherein the plate workpiece has a pair of opposite faces that are each juxtaposed in the furnace by a respective such shield formed of first and second parts.

13. The method of claim 10, further comprising the steps of: checking the cooled workpiece and, if the areas of different strength do not comply with a predetermined desired position or size, adjusting the position of the second part inside the furnace.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0036] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

[0037] FIG. 1 shows a shield frame according to the invention;

[0038] FIG. 2 shows the shield frame without the workpiece;

[0039] FIG. 3 shows the shield frame with the workpiece; and

[0040] FIGS. 4 and 5 are section taken along respective lines IV-IV and V-V of FIG. 3.

SPECIFIC DESCRIPTION OF THE INVENTION

[0041] As seen in the drawing, a shield 1 serves for covering at least part of a plate workpiece 2 while the plate workpiece 2 is being tempered in a furnace. This shield 1 and the plate workpiece 2 are heated to approximately the austenitization temperature in the furnace while a part of the plate workpiece 2 is covered by the shield 1 to reduce its heating and prevent it from reaching the austenitization temperature. The furnace is not shown in the figures. The four arrows 18 in each of FIGS. 4 and 5 represent the thermal radiation in the furnace. Thus the unshielded area of the plate workpiece 2 is kept or heated to the austenitization temperature by thermal radiation in the furnace.

[0042] The shield 1 comprises two first shield parts 3, 3′, two second shield parts 4, 4′, and two third shield parts 5, 5′, all movable relative to each other. The second shield parts 4, 4′ and the third shield parts 5, 5′ are detachably mounted on inner edges 6, 6′ of the first shield parts 3, 3′. The third shield parts 5, 5′ are attached to opposite inner edges 7, 7′ in a detachable and adjustable manner. The second and the third shield parts 4, 4′ and 5, 5′ can be detached in order to achieve an optimal shape, and the third shield parts 5, 5′ are additionally fastened adjustably to the respective first shield parts 3, 3′. In the illustrated position of the second shield parts 4, 4′ and the third shield parts 5, 5′, the predetermined region of the plate workpiece 2 is covered. The parts of the plate workpiece 2 are shielded by the shield 1 in a without direct contact.

[0043] The first shield part 3 with the second shield part 4 attached thereto and the third shield part 5 sit atop the first shield part 3′ with the second shield part 4′ attached thereto and the third shield part 5′. The shield parts 3, 3′ and the second and third shield parts 4, 4′ and 5, 5′ are constructed and adjusted congruently to one another. The plate workpiece 2 is held in the furnace sandwiched between the frame-like subassembly of the shield parts 3, 4, 5 on its upper face and the identical frame-like subassembly of the shield parts 3′, 4′, and 5′ on its lower face and thus is evenly shielded on both faces.

[0044] If the second and the third shield parts 4, 4′, 5, 5′ are set in a desired position or attached to the respective first shield part 3, 3′, the predetermined regions of the plate workpiece 2 are optimally covered. A check of the shield 1 is necessary to determine and set the target position. The attachment of the second and third shield parts 4, 4′, 5, 5′ to the first shield part 3, 3′, as well as the shape of the second and third shield parts 4, 4′, 5, 5′ are checked. The check is not based on the shield 1 itself, but rather, as described in the prior art, on the basis of a molded part that is formed and hardened from a plate workpiece 2 that was covered with the shield 1 when austenitizing heat was applied. If the check establishes that the areas of different strength are not in the predetermined areas, the shield 1 must be revised. During revision, the second and third shield parts 4, 4, 5, 5 are to be processed and/or adjusted in such a way that the desired shielding of the intended areas can take place.

[0045] For this purpose, the second shield parts 4, 4′ are detachably fastened to the respective first shield parts 3, 3′. The detachability allows replacement of the second shield parts 4, 4′ by more suitable and differently shaped and/or constituted second shield parts or an inexpensive and particularly simple postprocessing of the second shield part 4, 4′.

[0046] For postprocessing, the second shield parts 4, 4′ can be detached from the first shield parts 3, 3′ and processed as separate parts, which makes handling considerably easier since the entire shield 1 is no longer removed from the furnace and transported and processed. During postprocessing, material is removed from an edge 11 of the shield part 4, 4′. The postprocessed second shield part 4, 4′ is fastened to the respective first shield part 3, 3′ in the desired position after it has been processed. FIGS. 1, 2, 3 and 5 show the second shield parts 4, 4′ in a preassembly position, in which there are still gaps 12 between the second shield part 4, 4′ and the first shield part. A sectional view is shown in FIG. 5 and shows, among other things, fasteners 17, 17′ that secure the respective second shield parts 4, 4′ to the first shield parts 3, 3′. The fasteners 17, 17′ pass through the gap 12 at this point. In the target position, the second shield parts 4, 4′ abut flatly against the inner edges 6, 6′ of the first shield parts 3, 3′, without gap being formed.

[0047] If too much material is inadvertently removed during postprocessing of the edge region 11, the second shield part 4, 4′ can for example be exchanged for another replacement shield part. It is no longer necessary to replace the entire shield 1, which means that the costs arising from such faulty processing can be significantly reduced.

[0048] The third shield parts 5, 5′ are detachably and adjustably attached to the respective first shield parts 3, 3′. This makes it possible to replace or rework the third shield parts 5, 5′ in the manner described with reference to the second shield parts 4, 4′. It is also possible to set or optimize the desired position by adjusting the third shield parts 5, 5′ on the first shield parts 3, 3′, without the third shield part 5, 5′ having to be detached from the first shield part 3, 3′. The third shield parts 5, 5′ are adjusted relative to the first shield parts 3, 3′. The adjustability of the third shield part 5, 5′ is a particular advantage since the shield 1 no longer has to be removed from the furnace to set the target position of the third shield part 5, 5′, and an adjustment can also be made inside the furnace.

[0049] The adjustability can be useful with any form of shield part. In the illustrated embodiment, the adjustment is used for third shield parts 5, 5′ having respective edges 13, 13′ which has a shape based on a rectilinear grid, namely straight edges without irregularities that run parallel to likewise straight edges 14, 14′ of the plate workpiece to be shielded, which is shown in FIG. 3.

[0050] In the case of the second shield parts 4, 4′, a detachable connection to the first shield parts 3, 3′ with the possibility of postprocessing of the second shield part 4, 4′ is preferred in this embodiment, since the edge regions 11 of the second shield parts 4, 4′ have a corrugated shape which is not a straight line, but is an irregularly extending contour, such as a wave, as shown in FIGS. 1, 2 and 3. In this illustrated embodiment, an adjustment would not lead to the desired result if, for example, the corrugations were not sharp enough. Postprocessing can therefore be useful for this second shield part 4, 4′. Additional adjustability is not excluded.

[0051] The plate workpiece 2 is fixed in the furnace independently of the shield 1, for example sitting on supports 15 in the furnace, and is not moved when the second or third shield parts 4, 4′, 5, 5′ are adjusted.

[0052] The third shield part 5, 5′ can be adjusted outside or inside the furnace, with an adjustment inside the furnace being particularly advantageous since there is then no need for a complex removal of the shield 1 from the furnace. For adjustment, the third shield part 5, 5′ is adjustably fastened to the first shield part 3, 3′ by spindles 16, 16′ shown in FIG. 4. The spindles 16, 16′ form an inexpensive and simple solution for attaching the third shield parts 5, 5′ to the respective first shield parts 3, 3′ and adjusting them relative to it. Adjustment is made with an electric servomotor, for example.

[0053] As shown in FIGS. 1 and 2, the outer edges 7, 7′ of the first shield part 3, 3′ have, over the length of the third shield parts 5, 5′ attached thereto, first lips 8, 8′ facing the third shield part 5, 5′ and projecting away from the respective edge 7, 7′. The third shield parts 5, 5′ also has further lips 9, 9′ facing and projecting toward the edges 7, 7′. The first lips 8, 8′ and the further lips 9, 9′ overlap at least partially parallel to a plane of the shield 1. The shield 1 thus is formed between the edges 7, 7 ‘of the first shield parts 3, 3’ and the third shield parts 5, 5′ in the target position of the third shield part 5, 5′ with a Z-shaped gap 10 extending transversely to a plane of the shield 1 with the gaps of the first lips 8, 8′ and the further lips 9, 9′ being at least partially offset so radiant heat cannot pass through the shield 1. This is shown in the sectional view in FIG. 4. As a result, heat is prevented from entering the plate 2 lying under the gap 10. The first lip 8, 8′ is a first strip and the further lip 9, 9′ is designed as a further strip. Such strips can be attached to the shield 1 in a simple manner to form the lips 8, 8′ and 9, 9′.

[0054] The shield 1 can be precisely and quickly adapted to a workpiece to be shielded in a simple manner. In addition, flexible use of the shield 1 is possible, since it is possible to use the first shield parts 3, 3′ as the basis for a large number of similar workpiece and only the second and/or third shield parts 4, 4′, 5, 5′ need be exchanged or attached to the first shield parts 3, 3′ in order to adjust the shield 1 to another workpiece. As a result, a completely new shield 1 no longer has to be produced for each new workpiece.

[0055] In this way, a particularly cost-effective shield 1 can be provided for a large number of workpiece.

[0056] The invention is not limited to the illustrated embodiment, but is variable in many ways within the scope of the disclosure.

[0057] All individual and combination features disclosed in the description and/or drawing are regarded as essential to the invention.