WO2022218455A1

WO2022218455A1 - Component, and method for producing a component using forming technology

Info

Publication number: WO2022218455A1
Application number: PCT/DE2022/000028
Authority: WO
Inventors: Daniel Schoener; Holger NAECKEL
Original assignee: Neumayer Tekfor Engineering Gmbh
Priority date: 2021-04-12
Filing date: 2022-03-18
Publication date: 2022-10-20
Also published as: DE102021001875A1

Abstract

The invention relates to a component (2) which is produced from a blank (1) using forming technology, the blank (1) having a carbon content greater than 0.2 wt.%. The component (2) is produced from the blank (1) using the following steps: In a first step (101), the blank (1) is heated to a temperature above a temperature of the blank (1) at which the blank (1) begins to austenitise. In a second step (102), the blank (1) heated in the first step is sheared and undergoes final forming. In a third step (103), the formed blank (1) is subjected to a controlled cooling procedure. The invention also relates to a method for producing a component (2) from a blank (1) using forming technology.

Description

Component and method for forming a component

The present invention relates to a component. Furthermore, the invention relates to a method for producing a component by forming.

It is known in the prior art to produce geometries in metal components by means of cold or hot forming. A combination of cold and hot forming can also be carried out, in which hot pre-pressing is carried out first and then cold, finish-pressing. Moreover, warm forging is also known. Forming processes that take place at a temperature above 1,000 °C are referred to as hot forming. After hot forming, cold forming or machining is usually required on the functional surfaces in the prior art. Temperatures between 700 °C and 900 °C (occasionally also up to 1,050 °C) are warm forging. As a rule, cold forming leads to a high degree of accuracy, whereas lower forming forces are required for hot forming and higher degrees of forming can be achieved.

A production sequence known in the state of the art consists of the following steps: hot forming, blasting, soft annealing, blasting, coating, warm forming, machining, case hardening, blasting and hard machining.

An alternative process provides: hot forming, soft annealing, blasting, coating, cold forming, machining, case hardening, blasting and hard machining.

The prior art therefore has the disadvantage that the process chains for producing components in which hot/cold or hot/warm forming and subsequent case hardening take place have many individual steps. This leads to a correspondingly long production time, increases costs and is also disadvantageous in terms of energy, since energy has to be expended for each step. DE 100 65 737 A1, DE 102012 017525 A1, US 2016/0361784 A1 or DE 19734563 C1, for example, disclose methods for producing components such as bevel gears, gear wheels or roller bearing rings.

The object on which the invention is based is to improve the metal forming production of components with regard to the energy balance.

According to a first teaching, the invention solves the problem with a component. According to a second teaching, the object is achieved by a method for producing a component by forming.

The object is achieved according to the invention by a component which has been produced from a blank by forming, the blank having a carbon content greater than 0.2 percent by weight. In one embodiment, the blank preferably has a carbon content of between 0.4 percent by weight and 0.7 percent by weight.

The blank from which the component has been produced by means of a forming process is therefore not made from a customary or common case-hardening steel because it has a higher carbon content.

Various heat treatment methods are known to make steel harder and thus more wear-resistant. A significant influencing factor is the proportion of carbon in the steel, which "hardens" the steel through special effects under the influence of temperature and subsequent cooling. The so-called case hardening steel is used in the prior art. This is steel with a relatively low carbon content, typically less than 0.2 percent by weight. Carbon is added to harden the steel or the components. This happens over a longer period of time and at appropriate temperatures in a carbonaceous atmosphere. The carbon slowly diffuses into the component to a certain depth, which depends on the duration of the treatment. Due to temperature and cooling effects, the component is hardened at the points to which the carbon has diffused. In the component according to the invention, a high-carbon steel is used for the blank, which has a z. B. has a sufficiently high proportion of carbon for a heat treatment.

According to the invention, the component has been produced from the blank in at least the following steps: in a first step, the blank has been heated to a temperature—preferably between 800° C. and 1,050° C.—above a temperature at which austenitization of the blank begins that in a second step the blank heated in the first step has been sheared off and completely formed, and that in a third step the formed blank has been subjected to controlled cooling.

In particular, no such heating is carried out in the second step, so that it would be hot working. In one configuration, the second step comprises warm forging. Due to the semi-hot forming (the temperature is below 1,050 °C) at the beginning of the manufacturing process instead of the hot forming customary in the prior art, the forming steps required in the prior art and, for example - in the case of a blank made of a high-carbon steel - case hardening can also be carried out omitted. In the prior art, for example, it would be necessary to carry out case hardening in the case of a blank made of case-hardening steel during warm forming. This step is not necessary with a blank made of a high-carbon steel. The advantage is a shortened production time and a reduced energy requirement. The invention is thus advantageously characterized by resource efficiency and by the reduction in energy requirements.

The semi-hot forming takes place at a temperature above a temperature at which austenitization of the material of the blank begins. This lower temperature value for austenitization depends on the material and is between around 850 °C and 1,050 °C for most materials. Austenitization means that as a result of a heat treatment of iron, ferrite is converted into austenite, i.e. the conversion of a body-centered cubic crystal structure into a mixed crystal consisting of iron and carbon, takes place. The temperature range in which austenitization takes place extends up to the melting point of the respective material. However, the warm working temperature is below the melting point. In one embodiment, the temperature of the semi-hot forming is at most 1,050°C. One advantage of semi-hot forming above the aforementioned temperature of the onset of austenitization is that—particularly in connection with heat treatment—complex geometries can be produced in the blank and corresponding components can be manufactured.

One configuration of the component provides that the component is a differential bevel gear. The peculiarity of this design is that a complex structure like that of a differential bevel gear is created from a material with a high carbon content.

One configuration of the component is that the blank is in the form of a rod.

One configuration of the component is that the second step is a Netshape forming process. If the component is a differential bevel gear, the forming above the temperature of the onset of austenitization in combination with the forging of the finished functional geometry in the second step, preferably using netshape forming, represents a special feature compared to the prior art In the case of a bevel gear, for example, the functional geometry is given by the toothing.

One configuration of the component provides that the component has such a predetermined core structure in a core area as was produced by cooling in the third step. Through the targeted cooling in the third step, a desired core structure is created in the component. In the third step, the carbon distribution essentially does not change and is essentially constant over the cross section of the component, in particular when using a high-carbon steel for the blank. One configuration of the component is that in the third step a specified core structure has been produced in a core area, and that the specified core structure is related to application characteristics of the component. The application characteristics relate z. B. on the hardness, toughness or fatigue strength that the component has to have for the application.

One configuration of the component provides that, before the first step, no heating of the blank that affects the material properties has been carried out. The blank itself may have been heated during its production. However, this would not be part of the manufacturing process of the component according to the invention. The blank is therefore still only characterized by its carbon content of more than 0.2 percent by weight. According to the invention, however, no preheating is required before the first step.

One configuration of the component consists in that, in the second step, a running gear has been produced by forming. In this embodiment, the running gearing is a functional geometry of the component, which is produced in the second step by forming.

One configuration of the component provides that a functional geometry generated in the second step has not undergone any further shape-changing processing. The second step gave the component its final functional geometry. Further forming or machining operations to create the desired functional geometry are no longer required. For example, if the component is a bevel gear, the functional geometry is the toothing, which is completely created in the second step. Further processing steps, which also produce special geometries, can follow the second step in the different configurations. However, this then refers to other sections of the component and not to the functional geometry. In the case of the bevel gear, for example, the toothing is not formed or subjected to machining. One configuration of the component is that in the second step the blank has heat at its disposal that was introduced into the blank in the first step. This saves the energy to be expended. In this embodiment, the semi-hot forming of the second step is therefore part of an interlinked heat treatment. By combining forming and heat treatment, the result is a very efficient and resource-saving overall process.

One configuration of the component provides that a depression has been produced in the blank and that after the third step the depression has been machined. In one embodiment, the indentation was produced in the second step and/or by forming. In one embodiment, the recess is a through hole. In an alternative embodiment, the recess has a base.

One configuration of the component is that after the third step, a side of the blank facing away from the functional geometry produced in the second step is machined. In this embodiment, the back of the functional geometry or z. B. the bottom, if the function geometry is arranged on the top, machined.

One configuration of the component provides that after the third step, a functional geometry of the blank produced in the second step is at least partially subjected to induction hardening. Induction hardening brings the surface to a desired value and hardness profile in terms of hardness.

One configuration of the component is that the component has martensite formation generated by the induction hardening and an initial hardness according to the carbon content on the surface (this is preferably the outside), and that the martensite formation is related to application characteristics - in particular hardness and / or toughness and /or fatigue strength - of the component. One embodiment of the component provides that only teeth of the functional geometry produced in the second step have been subjected to induction hardening. In this configuration, the functional geometry has teeth. In this configuration, the teeth are therefore a special form of the functional surfaces of the functional geometry. Therefore, in a general configuration, only the functional surfaces of the functional geometry produced in the second step have been subjected to induction hardening. The functional surfaces are primarily the sections or areas of the functional geometry that are exposed to the greatest mechanical stress when the component is used.

In a further embodiment, all sections of the component that are subject to mechanical stress, e.g. B. through contact with other components are subject to induction hardening.

One configuration of the component is that teeth and intermediate sections between the teeth of the functional geometry produced in the second step have been subjected to induction hardening.

One configuration of the component provides that functional surfaces and intermediate sections between the teeth of the functional geometry produced in the second step have been subjected to induction hardening.

One embodiment of the component provides that in the second step a functional geometry with teeth has been produced and that the component has a greater penetration depth of hardened material in a head area of the teeth than in the associated foot areas. The flanks of the teeth between the head area and the associated foot areas can have a variable depth of penetration.

One configuration of the component consists in the component being at least partially subjected to a surface treatment—in particular blasted—after the third step. One configuration of the component provides that the component has a substantially constant carbon content and that the hardness of the component is higher towards the outside than in a core area. The component thus has a hardness profile that decreases from the outside to the inside and that is comparable to the profile that is produced from blanks made of case-hardening steel according to the prior art. However, the carbon content is - in contrast to the components according to the prior art

- essentially constant over the entire component. This is a clear difference and it comes from using a blank with a higher carbon content.

One configuration of the component is that the component has been produced without a carburizing process.

According to a second teaching, the invention solves the problem with a method for producing a component—in particular a differential bevel gear—from a blank by metal forming, the blank having a carbon content greater than 0.2 percent by weight

- preferably between 0.4 percent by weight and 0.7 percent by weight -, the method having at least the following steps: that in a first step the blank is heated to a temperature - preferably between 800 °C and 1,050 °C - above a temperature of the blank in which austenitization takes place, that in a second step the blank heated in the first step is sheared off and completely formed, and that in a third step the formed blank is subjected to controlled cooling.

Configurations of the component and the process steps carried out for the production of the component are discussed in the preceding and following text. The explanations given there also apply accordingly to the procedure, so that it is not repeated here.

One embodiment of the method is that a netshape forming method is carried out in the second step. In one embodiment of the method, a predetermined core structure is produced in a core area in the third step. In one configuration, essentially no change in the carbon distribution is made in the third step. The carbon distribution is essentially constant over the entire cross section of the component, in particular when using a blank made of steel with a higher carbon content.

One embodiment of the method consists in that in the second step a running gear is produced by forming.

One embodiment of the method provides that heat is introduced into the blank in the first step and that the heat introduced is used in the second step.

One embodiment of the method consists in that—preferably in the second step and/or preferably by forming—a depression—in particular a continuous bore—is produced in the blank, and that after the third step the depression is machined.

One embodiment of the method provides that after the third step, a side of the blank facing away from the functional geometry produced in the second step is machined.

One embodiment of the method consists in that, after the third step, a functional geometry of the blank produced in the second step is at least partially subjected to induction hardening.

One embodiment of the method provides that only teeth of the functional geometry produced in the second step are subjected to induction hardening. In an alternative embodiment, teeth and intermediate sections between the teeth of the functional geometry produced in the second step are subjected to induction hardening. One embodiment of the method consists in the component being at least partially subjected to a surface treatment—particularly blasted—after the third step.

In particular, there are a number of possibilities for designing and developing the component according to the invention and the method according to the invention. For this purpose, reference is made on the one hand to the patent claims subordinate to the independent patent claims and on the other hand to the following description of exemplary embodiments in conjunction with the drawings. Show it:

1 shows a section through a blank and a spatial representation of a component produced according to the invention,

2 shows a section through a component according to the invention,

3 shows an enlarged detail of a section of a component in the area of a tooth,

4 shows a schematic progression of the carbon content along the depth of the component from the outer surface to the core area for a case-hardened steel and a steel used according to the invention, and

5 shows a schematic sequence of the production steps of the method according to the invention.

FIG. 1a) shows a section through a blank 1, which is circular-cylindrical and is rod material.

1 b) shows a component 2 in the form of a bevel gear produced from such a blank 1 . The functional geometry 20, which is required for the actual function of the component 2 and which must be produced particularly carefully for this purpose, consists of a toothing with alternating teeth and valleys. Overall, this is the running teeth 21 of the bevel gear 2.

In the middle of the component 2 there is a continuous recess 22 or recess. This recess 22 and the rear or underside 23 facing away from the functional geometry 20 have been partially machined or at least reworked. This is in contrast to the running teeth 21, which he witnessed once by a forming step.

The outside 25 or surface of the functional geometry 20 that can be seen here has only undergone a hardening treatment after the forming.

2 shows a section through a blank after forming and before a machining step.

For example, on the right-hand side you can see the gearing that was created by the forming. As can be seen from the longitudinal axis, the original cylindrical shape of the blank has become more of a ring-like structure.

From the outside 25 to the core structure in the core area 26 as the inner area of the component there is a constant carbon content which, due to the selection of the material of the blank, is above the value of case-hardening steel.

The continuous cutout 22 is circular-cylindrical in this example. Alternatively, the recess can be crowned or have a spline. The dashed lines indicate that the recess 22 and the side 23 facing away from the functional geometry are machined. At these points, which are not relevant to the actual function of the component, the geometry is not only generated by forming, but is also created by machining or brought into the desired final state. 3 shows an enlarged section through a tooth 200 of the functional geometry 20, ie the running geometry.

Adjacent to the tooth 200 there is a section 203 on the right and left, which can also be described as a valley.

The dashed line indicates the course of the hardness from the outside to the core area (cf. FIG. 2). It can be seen that the penetration depth in the head area 201 extends much deeper than in the foot area 202 . Thus, the tip or head of the tooth 200 has been hardened over a larger area than the root area 202 and thus also the valley-shaped areas between the teeth 200.

4 shows the course of the carbon content c in a case-hardened steel (solid line) and a steel used according to the invention with a higher carbon content (dashed line).

The values are plotted against the edge distance t. As the enlargement of a tooth makes clear, the edge distance t is measured from the surface of the component in the direction of the core area (cf. Fig. 2).

It can be clearly seen that the carbon content has the same value over the entire depth - i.e. over every edge distance t - in steel with a higher carbon content. This is due to the fact that the blank already has a high carbon content and that it is not necessary to increase the carbon content through a machining process. In the prior art, this always leads to the carbon content being higher at the edge than in the core area, since the carbon has been introduced into the component from the surface. This is shown by the solid line for case hardening steel. In the case of case hardening steel, the hardness also decreases from the outside inwards, ie with a larger edge distance t. In the case of the steel with a higher carbon content used according to the invention, the course of hardness results from the induction hardening carried out, for example. FIG. 5 shows an embodiment of a flow chart of the forming method according to the invention. In the first step 101, the blank is subjected to heating. In one variant, the blank has a carbon content greater than 0.2 percent by weight. In the second step 102, the functional geometry is finished by semi-hot forming. This is preferably done at a temperature above the temperature at which austenitization of the material of the blank takes place, but below 1050°C. The function geometry then does not require any processing that affects the geometry. In the third step 103, the formed blank is subjected to controlled cooling, which in one embodiment is followed by machining. In a further treatment, at least part of the functional geometry is induction hardened.

Claims

patent claims

1. Component (2) which has been produced from a blank (1) by forming, the blank (1) having a carbon content greater than 0.2 percent by weight - preferably between 0.4 percent by weight and 0.7 percent by weight - wherein the Component (2) has been produced from the blank (1) at least with the following steps: that in a first step (101) the blank (1) to a temperature - preferably between 800 ° C and 1,050 ° C - above a temperature of the blank (1) has been heated, during which austenitization of the blank (1) begins, that in a second step (102) the blank (1) heated in the first step has been sheared off and completely formed, and that in a third step (103 ) the formed blank (1) has been subjected to controlled cooling.

2. Component (2) according to claim 1, wherein the component (2) is a differential bevel gear.

3. Component (2) according to claim 1 or 2, wherein the component (2) has such a predetermined core structure in a core region (26) as was produced by the cooling in the third step (103), and wherein the predetermined core structure in the core area (26) relates to application characteristics--in particular hardness and/or toughness and/or fatigue strength--of the component (2).

4. Component (2) according to one of claims 1 to 3, wherein the component (2) has a martensite formation produced by the induction hardening and an initial hardness according to the carbon content on a surface, and wherein the martensite formation is related to application characteristics - in particular hardness and / or toughness and/or fatigue strength - of the component (2).

5. Component (2) according to one of claims 1 to 4, wherein a functional geometry with teeth (200) has been generated in the second step, and wherein the component (2) is in a head area (201) of the teeth (200 ) has a higher penetration depth of hardened material than in associated foot areas (202).

6. Component (2) according to one of claims 1 to 5, wherein the component (2) has a substantially constant carbon content, and wherein a hardness of the component (2) in the direction of the outside (25) is higher than in a core area ( 26) is.

7. A method for producing a component (2) - in particular a differential bevel gear - by metal forming from a blank (1), the blank (1) having a carbon content greater than 0.2 percent by weight - preferably between 0.4 percent by weight and 0.7 percent by weight - has, wherein the method has at least the following steps: that in a first step (101) the blank (1) to a temperature - preferably between 800 ° C and 1,050 ° C - is heated above a temperature of the blank (1) at which austenitization of the blank (1) begins, that in a second step (102) the blank (1) heated in the first step is sheared off and completely formed, and that in a third step (103) the formed blank (1) undergoes controlled cooling is subjected to.

The method of claim 7, wherein heat is applied to the blank (1) in the first step (101) and the applied heat is used in the second step (102).

9. The method according to claim 7 or 8, wherein the second step (102) is a netshape transformation process.

10. The method according to any one of claims 7 to 9, wherein in the third step (103) a predetermined core structure is generated in a core region (26).

11. The method according to any one of claims 7 to 10, wherein in the second step (102) a running gear (21) is produced by forming.

12. The method according to any one of claims 7 to 11, wherein - preferably in the second step (102) and / or preferably by forming - a depression (22) - in particular a through bore - is produced in the blank (1), and wherein after the third Step (103) the recess (22) is machined.

13. The method according to claim 7, wherein after the third step (103) a side (23) of the blank (1) facing away from a functional geometry (20) generated in the second step (102) is machined.

14. The method according to any one of claims 7 to 13, wherein after the third step (103) a functional geometry (20) of the blank (1) produced in the second step (102) is at least partially subjected to induction hardening, and wherein only teeth ( 200) or teeth (200) and intermediate sections (203) between the teeth (200) of the functional geometry (20) produced in the second step (102) are subjected to induction hardening.