Patent Application
20230072974
The present disclosure relates to a method of manufacturing cast iron components for industrial equipment. More specifically, the present disclosure relates to a method of manufacturing a high-strength cast iron pump impeller or other cast iron component.
High pressure fluid movement is required in various industries, for example, industries which revolve around or require industrial equipment for mining, milling, earth-handling or manufacturing. The pumps used by these types of industries are often required to move large volumes of high viscosity material at high rates. This requires pump impellers made of high strength materials which are not susceptible to breakage.
It has been determined that existing methods of manufacturing cast iron components can be improved to increase the strength of the components (e.g., pump impeller) after being formed and machined. The methods discussed herein allow the cast iron components to be formed in desired shapes, machined, and still maintain a desirable hardness when complete. This leads to increased durability and run time, which reduces product failure and replacements resulting in a massive advantage in the field of pump impellers.
In view of the state of the known technology, a first aspect of the present disclosure is to provide a method of forming a cast iron component for industrial equipment. The method includes forming the cast iron component in a predetermined shape, machining the cast iron component, heat treating the cast iron component by raising the temperature of the cast iron component to an upper temperature, and cryogenically heat treating the cast iron component by lowering the temperature of the cast iron component to a lower temperature.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the lower temperature is at or below 0° C.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the upper temperature is at or above 950° C.
In another aspect of the disclosure, which can be combined with any other aspect described herein, cryogenically heat treating the cast iron component includes lowering the temperature of the cast iron component to between about −70° C. and −80° C.
In another aspect of the disclosure, which can be combined with any other aspect described herein, cryogenically heat treating the cast iron component includes maintaining the cast iron component at about the lower temperature for between about 2 to 4 hours.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the method includes stress relieving the cast iron component before machining the cast iron component.
In another aspect of the disclosure, which can be combined with any other aspect described herein, forming the cast iron component includes forming the cast iron component as a single piece.
In view of the state of the known technology, another aspect of the present disclosure is to provide a method of improving the hardness cast iron components for industrial equipment. The method includes forming a first cast iron component into a predetermined shape using a first liquid mixture, the first cast iron component having a first hardness, increasing a concentration of at least one element in a second liquid mixture in comparison to the first liquid mixture, forming a second cast iron component into the predetermined shape using the second liquid mixture, the second cast iron component having a second hardness greater than the first hardness, and further increasing the second hardness of the second cast iron component by cryogenically heat treating the second cast iron component by lowering the temperature of the cast iron component to a lower temperature.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the at least one element is carbon.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the at least one element is molybdenum.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the method includes adding niobium to the second liquid mixture.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the method includes heat treating the first cast iron component by raising the temperature of the first cast iron component to a first temperature for a first duration, and heat treating the second cast iron component by raising the temperature of the second cast iron component to a second temperature for a second duration, the second temperature being lower than the first temperature.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the method includes heat treating the first cast iron component by raising the temperature of the first cast iron component to a first temperature for a first duration, and heat treating the second cast iron component by raising the temperature of the second cast iron component to a second temperature for a second duration, the second duration being less than the first duration.
In another aspect of the disclosure, which can be combined with any other aspect described herein, machining the first cast iron component at a first location, and machining the second cast iron component at the first location.
In view of the state of the known technology, another aspect of the present disclosure is to provide a method of improving the hardness cast iron components for industrial equipment. The method includes forming a first cast iron component into a predetermined shape using a first liquid mixture, heat treating the first cast iron component by raising the temperature of the first cast iron component to a first temperature for a first duration, the first cast iron component having a first hardness after heat treatment, forming a second cast iron component into the predetermined shape using a second liquid mixture, heat treating the second cast iron component by raising the temperature of the second cast iron component to a second temperature for a second duration, the second cast iron component having a second hardness after heat treatment, the second hardness greater than the first hardness, at least one of the second temperature being lower than the first temperature and/or the second duration being less than the first duration, and further increasing the second hardness of the second cast iron component by cryogenically heat treating the second cast iron component by lowering the temperature of the cast iron component to a lower temperature.
In another aspect of the disclosure, which can be combined with any other aspect described herein, the method includes increasing a concentration of at least one element in a second liquid mixture in comparison to the first liquid mixture.
Also, other objects, features, aspects and advantages of the disclosed system and method will become apparent to those skilled in the art in the pump impeller field from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of pump impeller strengthening methods with various features.
The invention will be explained in more detail hereinafter with reference to the drawings.
Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
In the illustrated embodiment show in
The methods described herein are particularly advantageous when used to manufacture or otherwise improve a pump impeller or rotor to be used with Eddy Pump equipment, for example, as shown and described in the Eddy Pump Corporation's U.S. patents and publications. In an embodiment, the pump impeller 32 is a pump impeller or rotor as shown or described in one or more of U.S. Pat. Nos. 10,480,524 and 10,883,508 and U.S. Publication Nos. 2018/0142691 and 2019/0383305, the structure and requirements of each of which are incorporated herein by reference. The industrial equipment described herein can thus include the Eddy Pump equipment described in these patents and publications.
The cast iron component 30 is formed as a single piece of cast iron. More specifically, in the illustrated embodiment of the pump impeller 32, the shaft 38 and plurality of vanes 40 are formed as a single piece of cast iron. In the illustrated embodiment, the cast iron is white cast iron. As should be understood by those of ordinary skill in the art from this disclosure, white cast irons are hard and brittle, but cannot be easily machined. The method 10 discussed herein allows the white cast iron to be formed and machined while having an improved hardness at the end of the process.
Table 1 shows the chemical compositions of Samples 1 and 2 in comparison to the ASTM A532 standard. The ASTM A532 standard covers a group of white cast irons that have been alloyed to secure high resistance to abrasive wear for applications such as mining, milling, earth-handling, and manufacturing. The chemical compositions of Samples 1 and 2 in Table 1 were determined by X-ray fluorescence (XRF) and combustion methods per ASTM 1019.
As shown, Sample 2 has a lower overall carbon concentration in comparison to Sample 1, leading to the decreased martensite shown in
Table 2 shows the Rockwell “C” Scale hardness of Samples 1 and 2 in comparison to the ASTM A532 standard.
As illustrated, neither Sample 1 nor Sample 2 meet the ASTM A532 standard, although Sample 1 is closer than Sample 2. Although more easily machined, Sample 2 has a lower hardness than Sample 1 and the minimum required to meet the ASTM A532 standard. The method 10 disclosed herein strengthens Sample 2 to meet or exceed the hardness of Sample 1 and the ASTM A532 standard. The method 10 disclosed herein thus allows a cast iron component 30 (e.g., pump impeller 32) to be formed and machined with the resulting product meeting or exceeding the ASTM A532 standard.
Referring again to
In an embodiment, forming the cast iron component 30 includes smelting iron ore. In an embodiment, forming the cast iron component 30 includes mixing iron ore with alloys to create a liquid mixture. In an embodiment, forming the cast iron component 30 includes pouring the liquid mixture into one or more molds. The one or more molds define the predetermined shape of the cast iron component 30. In an embodiment, forming the cast iron component 30 includes allowing or causing the liquid mixture to cool and solidify within the one or more molds. More specifically, the liquid mixture cools and solidifies so that the cast iron component 30 is a single piece. Once the cast iron component 20 has solidified, the molds can be removed.
At step 14 of the method 10, a stress relief process is performed on the cast iron component 30. In an embodiment, stress relieving the cast iron component 30 includes soaking the cast iron component 30. In an embodiment, stress relieving the cast iron component 30 includes a heating portion and a cooling portion. In an embodiment, the heating portion includes heating the cast iron component 30 to between 550° C. and 650° C. In an embodiment, the cooling portion includes furnace cooling. In an embodiment, the cooling portion includes cooling the cast iron component 30 to a temperature less than about 100° C. Those of ordinary skill in the art will understand from this disclosure that other stress relieving processes can also be used.
At step 16 of the method 10, the cast iron component 30 is machined. In an embodiment, the pump impeller 32 is machined for a specific application. For example, the shaft 38 and/or vanes 40 are machined for a specific application. In an embodiment, the shaft 38 is machined to mate with another part of a pump. In an embodiment, the vanes 40 are machined to affect fluid flow, for example, when operating at high rates and/or moving large volumes of high viscosity material. In an embodiment, the cast iron component is machined at one or more particular locations, for example, a first location, a second location, etc.
In an embodiment, machining the cast iron component 30 includes milling the cast iron component 30 using a milling machine. In an embodiment, the milling machine includes a cutting edge which can be used to machine the cast iron component 30. In an embodiment, the milling machine can have multiple cutting edges. In an embodiment, the cast iron component is milled at one or more particular locations, for example, the first location, the second location, etc. Those of ordinary skill in the art will understand from this disclosure that other machining processes can also be used.
At steps 18 and 20 of the method 10, the cast iron component 30 undergoes a two-step heat treatment which improves the overall hardness of the cast iron component 30 after the cast iron component 30 has been formed and machined. At the first step of the two-step heat treatment, step 18, the temperature of the cast iron component 30 is raised to at or above an upper temperature. At the second step of the two-step heat treatment, the temperature of the cast iron component 30 is lowered below a lower temperature.
At step 18 of the method 10, the cast iron component 30 receives heat treatment in which the temperature of the cast iron component 30 is raised to at or above an upper temperature. More specifically, the cast iron component 30 receives a destabilizing heat treatment. The destabilizing heat treatment destabilizes the austenite of the cast iron component 30. In an embodiment, the upper temperature is about 950° C., such that the cast iron component 30 is raised to at or above about 950° C. In an embodiment, the upper temperature is between about 950° C. and about 1150° C. Those of ordinary skill in the art will understand that the upper temperature can vary within this range depending on the particular cast iron component 30 being manufactured.
In an embodiment, the heat treatment at step 18 includes a heating portion and a quenching portion. The heating portion includes heating the cast iron component 30 to an upper temperature that is a predetermined temperature or within a predetermined temperature range. In an embodiment, the heating portion includes heating the cast iron component 30 to a predetermined temperature between about 950° C. and about 1150° C. In an embodiment, the quenching portion includes air quenching the cast iron component 30.
At step 20 of the method 10, the cast iron component 30 undergoes a heat treatment in which the temperature of the cast iron component 30 is lowered to at or below a lower temperature. More specifically, the cast iron component 30 undergoes a cryogenic heat treatment. In an embodiment, the lower temperature is below 0° C., or more preferably at about −76° C. In an embodiment, the cast iron component 30 is placed in a cryogenic chamber. In an embodiment, the cryogenic heat treating of the cast iron component 30 includes maintaining the cast iron component 30 at below 0° C. for a duration of time. In an embodiment, the cast iron component 30 is maintained at between about −50° C. and −100° C., preferably between about −60° C. and −90° C., more preferably between about −70° C. and −80° C., more preferably at about −76° C. In an embodiment, the cast iron component 30 is maintained at this lower temperature for between about 2 to 4 hours, more preferably for about 3 hours. Thus, in an embodiment, the cast iron component 30 is maintained at about −76° C. for 3 hours within the cryogenic chamber.
In an embodiment, the method 10 can be used to improve the hardness of cast iron components for industrial equipment.
At step 52 of the method 50, a first cast iron component 30a is formed into a predetermined shape. The first cast iron component 30a can be a cast iron component 30 as illustrated in
In an embodiment, the first cast iron component 30a is formed as discussed herein with respect to step 12 of the method 10. More specifically, the first cast iron component 30a is formed with a first liquid mixture. The first liquid mixture can be a mixture of iron ore and one or more alloy. The first liquid mixture can contain one or more of carbon, chrome, molybdenum, nickel, manganese, silicon, sulfur, and phosphorus.
In an embodiment, the first cast iron component 30a is stress relieved as discussed herein with respect to step 14 of the method 10.
In an embodiment, the first cast iron component 30a is machined as discussed herein with respect to step 16 of the method 10. In an embodiment, the first component is machined at a first location for a specific purpose. In an embodiment, the first component is also machined at a second location for a specific purpose.
In an embodiment, the first cast iron component 30a is heat treated as discussed herein with respect to step 18 of the method 10. More specifically, the first cast iron component 30a is heat treated by raising the temperature of the first cast iron component 30a above a first temperature for a first duration, as discussed herein. In an embodiment, the first temperature can be the upper temperature discussed herein with respect to step 18 of the method 10.
At step 54 of the method 50, the chemical composition, hardness or other property of the first cast iron component 30a is determined. For example, the Sample 2 discussed herein was formed using steps 12 to 18 of the method 10 discussed herein. Thus, for explanation purposes, if Sample 2 was from the first cast iron component 30a, then the chemical composition of the first cast iron component 30a could be determined as shown in Table 3 and/or the hardness of the first cast iron component 30a could be determined as shown in Table 4. Sample 2 could also be examined using an analysis similar to that shown with respect to
As illustrated, the weight percentage of many of the elements of the first cast iron component 30a are at the lower end of a range or significantly below the maximum of the ASTM A532 standard. In an embodiment, step 54 includes determining a weight percentage of at least one element of the first cast iron component 30a to be below a predetermined value (e.g., the corresponding ASTM A532 standard value). Further, the hardness of the first cast iron component 30a is below the minimum hardness of the ASTM A532 standard. In an embodiment, step 54 includes determining a hardness of the first cast iron component 30a to be below a predetermined value (e.g., the corresponding ASTM A532 standard value).
In an embodiment, step 54 includes determining the martensite content of the first cast iron component 30a. In an embodiment, step 54 includes determining the austenite content of the first cast iron component 30a. In an embodiment, step 54 includes determining the eutectic carbides of the first cast iron component 30a. In an embodiment, step 54 includes determining the metal carbide precipitates of the first cast iron component 30a. As discussed above, martensite, austenite, eutectic carbides and/or metal carbide precipitates can be indicative of hardness and abrasion resistance. For example, between Samples 1 and 2 discussed herein, Sample 1 is harder and more abrasion resistant than Sample 2.
Steps 56 to 66 of the method 50 can then be used to create a second cast iron component 30b which is identically shaped and/or machined as the first cast iron component 30a but with an increased hardness in comparison to the first cast iron component 30a.
At step 56 of the method 50, a second liquid mixture is created. The second liquid mixture differs from the first liquid mixture in chemical composition. Like the first liquid mixture, the second liquid mixture can be a mixture of iron ore and one or more alloy. Like the first liquid mixture, the second liquid mixture can contain one or more of carbon, chrome, molybdenum, nickel, manganese, silicon, sulfur, and phosphorus.
In an embodiment, a concentration of at least one element in the second liquid mixture is increased in comparison to the first liquid mixture. The concentration can be increased by adding at least one of carbon, molybdenum, and/or niobium to the second liquid mixture. In a preferred embodiment, niobium is added to the second liquid mixture to increase the concentration of niobium in the second liquid mixture in comparison to the first liquid mixture. In another embodiment, carbon is added to the second liquid mixture to increase the concentration of carbon in the second liquid mixture in comparison to the first liquid mixture. In another embodiment, molybdenum is added to the second liquid mixture to increase the concentration of molybdenum in the second liquid mixture in comparison to the first liquid mixture. In another embodiment, at least two of carbon, molybdenum and niobium are added to the second liquid mixture. In another embodiment, all three of carbon, molybdenum and niobium are added to the second liquid mixture.
In an embodiment, carbon is added to the second liquid mixture at step 56 when the majority of the first cast iron component 30a is determined to be austenite at step 54. In a preferred embodiment, niobium is added to the second liquid mixture at step 56 when the first cast iron component 30a is determined to have minimal eutectic carbide at step 54. In another embodiment, carbon is added to the second liquid mixture at step 56 when the first cast iron component 30a is determined to have minimal martensite at step 54.
At step 58 of the method 50, a second cast iron component 30b is formed. More specifically, the second cast iron component 30b is formed into the predetermined shape. In an embodiment, the second cast iron component 30b is formed as discussed herein with respect to step 12 of the method 10. The second cast iron component 30b is formed with the second liquid mixture. In an embodiment, the second cast iron component 30b has the same predetermined shape as the first cast iron component 30a. The predetermined shape of the second cast iron component 30b can be that of the cast iron component 30 as illustrated in
At step 60 of the method 50, the second cast iron component 30b is stress relieved. In an embodiment, the second cast iron component 30b is stress relieved as discussed herein with respect to step 14 of the method 10. In an embodiment, the second cast iron component 30b is stress relieved at step 60 in the same manner that the first cast iron component 30a was stress relieved at step 52.
At step 62 of the method 50, the second cast iron component 30b is machined. In an embodiment, the second cast iron component 30b is machined as discussed herein with respect to step 16 of the method 10. In an embodiment, the second cast iron component 30b is machined at the same first location that the first cast iron component 30a was machined at during step 52. In an embodiment, the second cast iron component 30b is also machined at the same second location that the first cast iron component 30a was machined at during step 52.
At step 64 of the method 50, the second cast iron component 30b is heat treated. In an embodiment, the second cast iron component 30b is heat treated as discussed herein with respect to step 18 of the method 10. More specifically, the second cast iron component 30a is heat treated by raising the temperature of the second cast iron component 30a above a second temperature for a second duration. In an embodiment, the second temperature can be the upper temperature discussed herein with respect to step 18 of the method 10. In an embodiment, the second temperature is less than the first temperature used for heat treatment of the first cast iron component 30a during step 52. In an embodiment, the second duration is less than the first duration used for heat treatment of the first cast iron component 30a during step 52. In an embodiment, both the second temperature is less than the first temperature and the second duration is less than the first duration.
In an embodiment, the second temperature and/or second duration is determined based on the determination made at step 54. In an embodiment, if the first cast iron component 30a is determined to have minimal and/or large metal carbide precipitates at step 54, the second temperature is made to be less than the first temperature used for heat treatment of the first cast iron component 30a during step 52. In an embodiment, if the first cast iron component 30a is determined to have minimal and/or large metal carbide precipitates at step 54, the second duration is made to be less than the first duration used for heat treatment of the first cast iron component 30a during step 52. In an embodiment, if the first cast iron component 30a is determined to have minimal and/or large metal carbide precipitates at step 54, both the second temperature is made to be less than the first temperature and the second duration is made to be less than the first duration.
At step 66, the second cast iron component 30b undergoes a cryogenic heat treatment. In an embodiment, the second cast iron component 30b undergoes the cryogenic heat treatment as discussed herein with respect to step 16 of the method 10. More specifically, the second cast iron component 30b undergoes a heat treatment in which the temperature of the second cast iron component 30b is lowered to at or below a lower temperature. As discussed above, in an embodiment, the lower temperature is below 0° C., or more preferably at about −76° C. In an embodiment, the second cast iron component 30b is maintained at below 0° C. for a duration of time. In an embodiment, the second cast iron component 30b is maintained at between about −50° C. and −100° C., preferably between about −60° C. and −90° C., more preferably between about −70° C. and −80° C., more preferably at about −76° C. In an embodiment, the second cast iron component 30b is maintained at this lower temperature for between about 2 to 4 hours, more preferably for about 3 hours. Thus, in an embodiment, the second cast iron component 30b is maintained at about −76° C. for 3 hours.
Table 6 illustrates how the hardness of the second cast iron component 30b improved in comparison to the first cast iron component 30a using the method 50. In Table 6, the hardness was increased from 56.9 to 59 by adding niobium to the chemical composition while staying in line with the higher end of the ASTM A532 Grade 3 ranges. This brought the hardness of the second cast iron component 30b in line with the ASTM A532 standard. This also created an unexpected result in that the hardness of 59 could be achieved by only adding niobium to the previous chemical composition. The hardness of the second cast iron component 30b was further increased from 59 to 61 by performing the cryogenic heat treatment at step 66. This further raised the hardness of the second cast iron component 30b above the minimum ASTM A532 standard. The increased hardness leads to durability and increased run time, which reduces product failures and replacements in this field.
The methods described herein can be used to create new cast iron components with desirable hardness and/or to improve the hardness of cast iron components made with existing molds and/or machining tools. It should be understood that various changes and modifications to the methods described herein will be apparent to those skilled in the an and can be made without diminishing the intended advantages.
In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such features. Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
This application claims priority to U.S. Provisional Application No. 63/237,203, filed Aug. 26, 2021, entitled “Method of Manufacturing Cast Iron Components for Industrial Equipment”, the entire contents of which is incorporated herein by reference and relied upon.
| Number | Date | Country | |
|---|---|---|---|
| 63237203 | Aug 2021 | US |
