Process for producing a component made of heat-treated cast iron

Abstract

The disclosure relates to a process for producing a hardened and tempered component made of specially heat-treated cast iron (e.g., AGI). According to the disclosure, a main body made of cast iron is prepared which may already be in the shape of an engine block. The main body may then be subjected to pre-machining, which may include forming one or more bores. Then, the main body may be hardened and tempered by a suitable heat treatment, such as a special heat treatment. After the disclosed heat treatment, post-processing of the component may follow, such as establishing the final dimensions.

Claims

1. A process comprising: casting an engine block main body from a cast iron; boring the main body to form a bore having a first shape; heat treating the main body having the bore to establish an ausferritic microstructure of the main body and the bore having a second shape; and machining the bore having the second shape after the heat treating step.

2. The process of claim 1, wherein the main body is heated to a temperature of 850 C. to 950 C. during the heat treating step.

3. The process of claim 1, further comprising cooling the main body in a salt bath after the heat treating step.

4. The process of claim 3, wherein the salt bath has a temperature of 220 C. to 450 C.

5. The process of claim 1, wherein the machining step includes threading the bore with a mechanical process to form a thread on the bore after the heat treating step.

6. The process of claim 1, wherein the heat treating step establishes an at least 90% ausferritic microstructure in the main body.

7. The process of claim 1, wherein the heat treating step establishes a 100% ausferritic microstructure.

8. The process of claim 1, wherein the heat treating step is performed under a protective atmosphere.

9. The process of claim 1, wherein the one bore is a through bore or a partial bore.

10. A process comprising: casting an engine block main body from a cast iron; boring the main body to form a bore having a first shape; heat treating the main body to establish an at least 90% ausferritic microstructure in the main body and the bore having a second shape; and machining the bore having the second shape after the heat treating step.

11. The process of claim 10, wherein the main body is heated to a temperature of 850 C. to 950 C. during the heat treating step.

12. The process of claim 10, further comprising cooling the main body in a salt bath after the heat treating step.

13. The process of claim 10, wherein the machining step includes threading the bore with a mechanical process to form a thread on the bore after the heat treating step.

14. The process of claim 10, wherein the heat treating step establishes a 100% ausferritic microstructure.

15. The process of claim 10, wherein the heat treating step is performed under a protective atmosphere.

16. The process of claim 10, wherein the bore is a through bore or a partial bore.

17. A process comprising: casting an engine block from a cast iron; boring the engine block to form a bore having a first shape; heat treating the engine block having the bore at a temperature of 850 C. to 950 C. to establish an at least 90% ausferritic microstructure in the engine block and the bore having a second shape; and machining the bore having the second shape after the heat treating step.

18. The process of claim 17, wherein the machining step includes threading the bore with a mechanical process to form a thread on the bore after the heat treating step.

19. The process of claim 17, further comprising machining the engine block after the heat treating step.

20. The process of claim 17, further comprising machining surface regions of the engine block after the heat treating step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a production process, for example for an engine block, according to the prior art; and

(2) FIG. 2 shows the diagram from FIG. 1, modified to include a production process, according to an embodiment.

DETAILED DESCRIPTION

(3) As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

(4) FIG. 1 shows, in stylized form, the typical production sequence for components made of normal cast iron (line GG, solid) and made of specially heat-treated cast iron (line AGI, solid). This proceeds from casting H1 the main body, via hardening and tempering the latter, through a special heat treatment H2 and the subsequent machining H3 to the finished component. The production sequence shown in diagrammatic form indicates, on its abscissa, information relating to the required time T with respect to the costs U, which analogously extend along the ordinate.

(5) In that context, the upper curve represents the production of a component AGI made of specially heat-treated cast iron, whereas the lower curve represents the production of a conventional cast iron component GG. As can be seen, the costs for producing components made of heat-treated cast iron are typically higher than with conventional cast iron components made of gray cast iron (GG). Here, in addition to the heat treatment H2, it is in particular the machining H3 which is responsible for these high costs. This is because the heat-treated main body is substantially harder, which leads to substantial wear of the processing tools, such that these have to be replaced early (e.g., obtained anew).

(6) FIG. 2 now shows the result that can be achieved with the process according to the disclosure, with respect to costs. In order to be able to better differentiate, here the component which can be made of specially heat-treated cast iron (e.g., an engine block) which is processed subsequent to the special heat treatment, is labeled AGIn. The graph AGIn is dotted. The component (e.g., an engine block) can be produced visibly more cost-effectively with the processes according to the disclosure.

(7) The cost savings in this context lie in particular in the machining H3 which, according to the disclosure, is divided into a pre-processing H3a and a post-processing, or finishing, H3b. Since the essential processing takes place in the context of the pre-processing H3a, there is a marked reduction in the effort and thus the costs in the post-processing, or finishing, H3b. However, it must be noted that the prior pre-processing process also involves costs, such that, at first, the graph AGIn lies above the graph AGI in the regions H3a and H2. However, this initial cost factor is more than compensated forand indeed is markedly reducedby the lower effort of processing and by the lower wear on the processing tools after the special heat treatment, as shown by the double arrow between the graphs AGI and AGIn. The double arrow represents the cost advantage of the procedure according to the disclosure over the conventional procedure.

(8) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.