Patent Application
20250073770
This application claims the benefit of Chinese Patent Application No. 202311096500.5 filed on Aug. 28, 2023. The entire disclosure of the application referenced above is incorporated herein by reference.
The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The present disclosure relates to manufacturing of press hardening steel (PHS) components, and more particularly to methods for improving a surface quality of coating-free press hardening steel (CFPHS) components.
Press hardening of steel (PHS) increases the strength of the steel. PHS is often used for load-bearing components of vehicles, construction equipment, and/or equipment for other industries. During press-hardening of steel, a steel blank is heated to a temperature range for austenitization, transferred to a stamp/press while hot, and formed and pressed between two or more dies of the stamp/press. In some examples, the steel blank is cold formed to an intermediate shape prior to austenitization and forming and pressing.
When the steel blank is uncoated, an oxide layer forms on a surface of the blank after austenitization during transfer to the stamp/press. The oxide layer needs to be removed after forming and pressing. For example, the oxide layer may be descaled by shot blasting, which increase cost and production cycle time. To avoid formation of the oxide layer, the steel blank may be coated with a coating layer that inhibits the formation of the oxide layer. For example, the steel blank may be coated with aluminum-silicon alloy (AISi) to inhibit the oxide coating and to avoid the cost and time required to remove the oxide layer.
A method for manufacturing a coating-free press hardening steel (CFPHS) component comprises heating a CFPHS blank at a first predetermined heating rate to a first predetermined temperature in a first predetermined temperature range using a heater; transferring the CFPHS blank to a furnace; soaking the CFPHS blank in the furnace at a second predetermined temperature in a second predetermined temperature range for a predetermined period; and pressing and forming the CFPHS blank in a stamp/press to form a CFPHS component.
In other features, the first predetermined temperature is from 500° C. to 950° C. The first predetermined heating rate is from 20° C./s to 300° C./s. The heater is selected from a group consisting of an induction heater, a resistance heater, a laser heater, or combinations thereof. The second predetermined temperature is from 750° C. to 1200° C. The predetermined period is in a range from 5 s to 500 s. The predetermined period is in a range from 5 s to 50 s.
In other features, after pre-heating in the heater, the CFPHS component includes an oxidation layer having a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.5 microns. The oxidation layer covers greater than or equal to 90% of an exposed surface of the CFPHS component. After pre-heating in the heater, the CFPHS component includes an oxidation layer having a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.0 microns.
A method for manufacturing a coating-free press hardening steel (CFPHS) component comprises heating a CFPHS blank using a heater to a first predetermined temperature in a range from 500° C. to 950° C. at a first predetermined heating rate in a range from 20 to 300° C./s; transferring the CFPHS blank to a furnace; soaking the CFPHS blank in the furnace for a predetermined period at a second predetermined temperature in a range from 750° C. to 1200° C.; and pressing and forming the CFPHS blank in a stamp/press to form a CFPHS component. After pre-heating in the heater, the CFPHS component includes an oxidation layer having a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.5 microns.
In other features, the heater is selected from a group consisting of an induction heater, a resistance heater, a laser heater, or combinations thereof. The predetermined period is in a range from 5 s to 500 s. The predetermined period is in a range from 5 s to 50 s. The oxidation layer has a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.0 microns. The oxidation layer covers greater than or equal to 90% of an exposed surface of the CFPHS component.
A method for manufacturing a coating-free press hardening steel (CFPHS) component comprises heating a CFPHS blank to a first predetermined temperature in a range from 500° C. to 950° C. at a first predetermined heating rate in a range from 20 to 300° C./s using one or more of induction heating, resistance heating, laser heating, or combinations thereof; transferring the CFPHS blank to a furnace; soaking the CFPHS blank in the furnace for a predetermined period in a range from 5 s to 50 s at a second predetermined temperature in a range from 750° C. to 1200° C.; transferring the CFPHS blank to a stamp/press; and pressing and forming the CFPHS blank in the stamp/press to form a CFPHS component. The CFPHS component includes an oxidation layer having a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.5 microns.
In other features, the oxidation layer has a thickness in a range from greater than or equal to 0.1 micron to less than or equal to 1.0 microns. The oxidation layer covers greater than or equal to 90% of an exposed surface of the CFPHS component.
Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
While the method for manufacturing coating-free press hardening steel (CFPHS) according to the present disclosure is described in the context of structural components for vehicles, the method for manufacturing CFPHS can be used for other applications.
During press-hardening of steel, a steel blank is heated to a temperature in a range for austenitization, transferred to a stamp/press while hot, and formed and pressed between two or more dies of the stamp/press. In some examples, the steel blank is cold formed to an intermediate shape prior to austenitization and forming and pressing.
To avoid formation of the oxide layer, the steel blank may be coated with a coating layer that inhibits the formation of the oxide layer. For example, the steel blank may be coated with an aluminum-silicon alloy (AlSi) layer to inhibit the oxide coating and avoid cost and time required to remove the oxide layer after pressing and forming. To reduce production time, the steel blank can be rapidly pre-heated using other heating methods prior to heating in the furnace (to reduce the amount of time required in the furnace). However, the AlSi-coated PHS is not compatible with rapid pre-heating. The AlSi coating layer melts without alloying due to the high heating rate.
During press hardening of steel (PHS) according to the present disclosure, a steel blank comprising coating-free PHS (CFPHS) is rapidly pre-heated. After rapid pre-heating, the steel blank is transferred to a furnace for a soaking period at a predetermined temperature and transferred to a stamp/press for pressing and forming of the CFPHS component. After pressing and forming the CFPHS component, there is no need for descaling, which reduces cost.
A method for manufacturing a coating-free press hardening steel (CFPHS) component is described in commonly assigned U.S. Patent Publication 2021002746, published on Jan. 7, 2021, which is hereby incorporated by reference in its entirety. As described therein, the CFPHS blank is hot stamped into a press-hardened component having a predetermined shape without coatings (and without a need to perform descaling).
The steel alloy used for the CFPHS blank comprises carbon (C), chromium (Cr), silicon (Si), and iron (Fe). During a hot stamping process, portions of the Cr and Si combine with atmospheric oxygen to form a first layer comprising an oxide enriched with the portions of the Cr and Si. When there is sufficient oxygen in the atmosphere, a portion of the Fe combines with atmospheric oxygen to form a second layer comprising an oxide enriched with Fe. The first and second layers prevent, inhibit, or minimize further oxidation such that descaling steps, such as shot blasting or sand blasting, are not required.
The C is present in the steel alloy at a concentration of greater than or equal to about 0.01 wt % to less than or equal to about 0.35 wt %. The Cr is present in the steel alloy at a concentration of greater than or equal to about 1 wt % to less than or equal to about 9 wt %. The Si is present in the steel alloy at a concentration of greater than or equal to about 0.5 wt % to less than or equal to about 2 wt %. The Fe makes up the balance of the steel alloy (unless additional elements (some of which are described below) are added).
In various embodiments, the CFPHS component further comprises manganese (Mn) at a concentration of greater than or equal to 0 wt % to less than or equal to 3 wt %. In various embodiments, the steel alloy further comprises nitrogen (N) at a concentration of greater than or equal to about 0 wt % to less than or equal to about 0.01 wt %. In various embodiments, the steel alloy further comprises molybdenum (Mo) at a concentration of greater than or equal to about 0 wt % to less than or equal to about 0.8 wt %. In various embodiments, the steel alloy further comprises boron (B) at a concentration of greater than or equal to about 0 wt % to less than or equal to about 0.005 wt %. In various embodiments, the steel alloy further comprises niobium (Nb) at a concentration of greater than or equal to about 0 wt % to less than or equal to about 0.3 wt %. In various embodiments, the steel alloy further comprises vanadium (V) at a concentration of greater than or equal to about 0 wt % to less than or equal to about 0.3 wt %.
Rapid pre-heating of the CFPHS blank improves the surface quality of CFPHS component and does not require descaling. The method for manufacturing CFPHS combines rapid pre-heating and furnace soaking so that optimal surface quality of the CFPHS can be obtained. A pre-formed protective oxidation layer is formed during rapid pre-heating. A shortened furnace heating soak is used to reduce oxidation time. In some examples, the CFPHS component is used for crash-resistant structural components such as automotive pillars, door beams, and bumper beams.
Referring now to
The heater 114 heats the CFPHS blank 110 at a first predetermined heating rate to a first predetermined temperature range. In some examples, the first predetermined heating rate is in a range from 20° C./s to 300° C./s. In some examples, the first predetermined temperature is in a range from 500° C. to 950° C. The final temperature of the CFPHS blank 110 will vary depending on a gauge and size of the CFPHS blank 110A. In some examples, the heater 114 is selected from a group consisting of an induction heater, a resistance heater, a laser heater, or combinations thereof.
After rapid pre-heating, the CFPHS blank 110 is transferred to a furnace 120 for heating. In some examples, the furnace 120 soaks the CFPHS blank 110 at a temperature in a range from 750° C. to 1200° C. In other examples, the furnace 120 soaks the CFPHS blank 110 at a temperature in a range from 900° C. to 950° C. In some examples, the CFPHS blank 110 is heated for a predetermined soak period in a range from 5 s to 500 s. In some examples, the CFPHS blank 110 is heated for a predetermined period in a range from 5 s to 50 s.
After heating in the furnace 120, the CFPHS blank 110 is transferred to a stamp/press 140 including two or more dies 144 for pressing and forming to create a pressed and formed CFPHS component 150.
The combination of the use of CFPHS, pre-heating, and soaking in the furnace (for a shorter soaking period) allows the desired surface quality and base metal mechanical properties to be obtained. In some examples, an oxidation layer on the CFPHS component has a thickness in a range greater than or equal to 0.1 micron and less than or equal to 1.5 microns. In some examples, the oxidation layer covers greater than or equal to 90% of an exposed surface of the CFPHS component. In some examples an oxidation layer on the CFPHS component has a thickness in a range greater than or equal to 0.1 micron and less than or equal to 1.0 microns.
Referring now to
At 230, after rapid pre-heating, the CFPHS blank is delivered to a furnace. At 232, the CFPHS blank is soaked for a predetermined soak period at a second predetermined temperature in the furnace. In some examples, the second predetermined temperature is in a range from 750° C. to 1200° C. In some examples, the second predetermined temperature is in a range from 900° C. to 950° C. In some examples, the CFPHS blank 110 is soaked for a predetermined soak period in a range from 5 s to 500 s. In some examples, the CFPHS blank 110 is soaked in the furnace for a predetermined period in a range from 5 s to 50 s.
At 240, after heating in the furnace, the CFPHS blank is transferred to a stamp/press including two or more dies. At 242, the CFPHS blank is formed and press hardened into the CFPHS component.
The method for manufacturing the CFPHS component according to the present disclosure produces components with a consistent desired surface quality. The method simplifies furnace atmosphere requirements (in other words, the furnace can operate using atmospheric air rather than nitrogen or another gas environment). The method for manufacturing the CFPHS component reduces energy consumption by reducing the heat treatment cycle time for CFPHS components.
The CFPHS components have improved appearance after spot welding and corrosion resistance after painting. The method for manufacturing the CFPHS components reduces cost by using CFPHS rather than coated PHS (e.g., AlSi-coated PHS) (avoiding descaling). The method for manufacturing CFPHS components also improves production efficiency of hot stamping due to the shorter furnace heating cycle, which reduces lead time.
The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.
Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”
In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023110965005 | Aug 2023 | CN | national |
