ROLL FORMING PROCESS WITH HEAT SOURCE LOCATIONS FOR FORMING A METAL ARTICLE WITH SELECTIVE THERMAL FORMING/FLANGING/TRIMMING OPERATIONS

Abstract

A process and assembly for heat treating portions of a metal article, such as an advanced high strength (AHSS) steel. In an initial operation, the invention provides for positioning of heating elements along a travel path of an unreeled sheet of a metal. Following an initial heating, an initial bending or forming is employed by a first roll pass to bend or reform the article with the heated zones defining the bend axles or points within the article. Following the initial heating and bending operations, additional heating elements can located, such as against outer flange locations of the previously bent article for further bending in response to a downstream located roll pass operation, following which a subsequent trimming or final fabricating step is employed to complete the article.

Description

FIELD OF THE INVENTION

The present invention relates generally to enhancing forming of metal articles. More specifically, the present invention teaches a process and assembly for heat treating portions of a steel article prior to and during a roll forming operation in order to enhance material properties of the steel as it is unrolled in order to increase formability and/or trim-ability.

BACKGROUND OF THE INVENTION

Advanced High Strength Steels (AHSS) are known in the relevant art which allow the down gaging, and therefor lightweighting, of automotive panels that take advantage of that material's higher strength. Those same material properties also make it challenging to form, flange and trim into a desired shape.

Stretch flanges are particularly troublesome to form utilizing these new materials. The higher strength and hardness associated with the newer height strength steels also are associated with the premature wear of the tooling edges used to trim the panel. The coupling of those issues can lead to production quality concerns that are challenging to resolve.

One example from the prior art is disclosed in U.S. Pat. No. 9,783,865 to Sachdev which teaches thermal assisted roll forming of a height strength material using a high-intensive heat source. The high-strength material may be a cold-rolled sheet aluminum of strength greater than 300 megapascal (MPa) or a cold-rolled sheet steel of strength greater than 1000 MPa. The cold-rolled sheet metal is heated just before bending to a temperature near or above the critical temperature for the material and is followed by rapid quenching after bending.

Other examples drawn from the relevant prior art include the press system and method of U.S. Pat. No. 10,618,094, to Martin Gonzalez, which teaches manufacturing hot formed structural components and includes a fixed lower body, a mobile upper body and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the fixed lower body. A cooling/heating tool is configured to cool down and/or heat a previously heated blank having locally different microstructures and mechanical properties, The tool includes each of upper and lower mating dies including two or more die blocks adapted to operate at different temperatures corresponding to zones of the blank having locally different microstructures and mechanical properties. A press tool is configured to draw the blank and is arranged downstream the cooling/heating tool.

Also disclosed is the method of forming a metallic article set forth in US 2012/0067100 to Stefansson et al., which teaches directly and/or indirectly inductively heating a localized region of a metallic article to a forming temperature. The metallic article may include materials selected from titanium alloys, nickel-base alloys, and specialty steels, e.g., stainless steel, high-strength low-alloy steel, armor steel alloys, and the like. The forming temperature may be in a forming temperature range of 0.2 to 0.5 of a melting temperature of the metallic article, which is then formed in the localized region. Stefansson further references roll forming as alternate methods for forming the metallic article however does not illustrate, teach or specify any particular process or assembly for forming the article via a roll forming process.

SUMMARY OF THE INVENTION

The present invention discloses a process and assembly for heat treating portions of a metal article, such as an advanced high strength (AHSS) steel. A coil steel roll is provided which feeds a continuous sheet (typically at an ambient temperature) through a series of roll passes corresponding to a roll forming operation for progressively shaping the steel sheet between an initial planar cross sectional shape and an eventual multi-sided cross section corresponding to a desired flange or bracket, such as which can be incorporated into a vehicle pillar, panel, beam or bracket.

One or more heat sources are provided at locations along the travel path of the steel sheet between selected roll passes. An initial heat source can be provided at the point the steel sheet is unreeled from the roll and prior to entering the first roll pass. The heat source includes one or more individual heating elements which can be provided in a linearly arrayed fashion to align with one or more desired bend axes in order to from the finished product.

A further heat source can be located at a downstream location, such as without limitation following a second roll pass, in order to apply an additional targeted or localized heating to one or more further selected bend or fold line locations of an intermediate formed article, prior to the article advancing through a further succeeding (typically final) roll forming pass in which a final cross sectional shape is imparted to the linearly fed article. Following this, any subsequent trimming or final fabricating step is employed to complete the article.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which:

FIG. 1 is a schematic view of a process and assembly for heat treating portions of a steel article, such as an advanced high strength (AHSS) steel, in which a coil steel roll is provided which feeds a continuous sheet (typically at an ambient temperature) through a series of roll passes corresponding to a roll forming operation for progressively shaping the steel sheet between an initial planar cross sectional shape and an eventual multi-sided cross section corresponding to a desired flange or bracket, such as which can be incorporated into a vehicle pillar, panel, beam or bracket;

FIG. 2 is a cross section taken along line 2-2 of FIG. 1 and depicting an initial pair of side-by-side located heat sources, such as which can be linearly arrayed and are provided at locations along the travel path of the steel sheet at the point the steel sheet is unreeled from the roll and prior to entering a first roll pass;

FIG. 3 is a cross section taken alone line 3-3 of FIG. 1 and depicting a first intermediate cross sectional configuration of the metal article in which the placement of the heating elements correspond to bend lines formed in the steel article as it advances through the first roll pass;

FIG. 4 is a cross section taken along line 4-4 of FIG. 1 and depicting further downstream located side-by-side heat sources at a downstream location, such as without limitation following a second roll pass, in order to apply an additional targeted heating to the selected bend or fold line locations of an intermediate formed article and prior to the article advancing through a further succeeding roll forming pass; and

FIG. 5 is a cross section taken along line 5-5 of FIG. 1, following a final roll pass, in which a final cross sectional shape is imparted to the linearly fed article.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the attached illustrations, the present invention discloses a process and assembly for heat treating localized portions of an ambient temperature metal article, such as in particular an advanced high strength steel, order to enhance the material properties of an associated roll forming process, this in order to increase formability, flange-ability and/or trim-ability as compared to strictly cold-rolling processes and without having to heat the entire steel material such as in a known hot-rolling process. In particular, the AHSS material is strategically heated at given locations as it is unreeled in roll or coil form and passed through succeeding roll pass operations in order to provide for tighter bend radii, and as compared again to such as strictly cold deformation of the steel. In this fashion, the present invention avoids instances of edge cracking or splitting inside of the trim line of the article.

As will be further described in reference to the attached illustrations, the present invention envisions the strategic application of thermal energy, such as in the placement of heating elements, in order to pre-heat locations of the steel sheet or blank (typically a flattened AHSS sheet but also contemplating the possibility of substituting high grade aluminum or other metals) prior to a series of succeeding roll pass operations being performed on the continuously fed sheet. The invention also contemplates one or more subsequent targeted heating steps associated with any downstream trimming or bending operation for producing a finished part, which can be achieved closer to a desired shape than is often otherwise attainable. The present process and assembly also allows for reduced application force in the progressive roll pass operations and finished fabrication steps.

FIG. 1 presents a schematic view, generally at 10, of a process and assembly for heat treating portions of a steel article, such as an advanced high strength (AHSS) steel, in which a coil steel roll 12 is provided which feeds a continuous sheet (typically at an ambient temperature) through a series of roll passes, see as depicted at 14, 16 and 18 and corresponding to a roll forming operation for progressively shaping the steel sheet between an initial planar cross sectional shape (again at 12) and an eventual multi-sided cross section corresponding to a desired flange or bracket (see at 12′″ in FIG. 5), such as which can be incorporated into a vehicle pillar, panel, beam or bracket.

As is known, roll forming involves the continuous bending of a long strip of a sheet metal (typically a coiled steel) in a desired cross section. The strip passes through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the overall bend/flange/trim operations, until the desired cross-section (profile) is obtained. As is further known, roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.

Referencing now FIG. 2, a cross section taken along line 2-2 of FIG. 1 depicts an initial pair of side-by-side located heat sources, depicted at 20 and 22 such as which can be linearly arrayed and are provided proximate the conveyed sheet, such as without limitation being positioned at locations along the travel path of the steel sheet 12 at the point the steel sheet is unreeled from the roll and prior to entering the first roll pass 14. Preferably, the heat sources are arranged to provide localized heating to the sheet 12 proximate to coaxial or coincidental bend lines or axes.

In a non-limiting application, the heating elements are positioned at specific locations underneath the steel sheet or blank and can be of any known type or construction which includes, without limitation, any of direct heating or other inductive heating elements for introducing a current to flow in a material by exposing it to an alternating magnetic field. As is further known, the alternating magnetic field is typically in the kHz range and is created using a resonating coil, resulting in heat being generated through resistance losses, as well as hysteresis losses in ferromagnetic materials like iron.

FIG. 3 is a cross section taken alone line 3-3 of FIG. 1 and depicting a first intermediate cross sectional configuration, at 12′ of the metal article resulting from the initial roll pass operation 14, and in which the placement of the heating elements 20/22 correspond to a series of the bend lines or bend axes formed in the steel article, at 24/26 and 28/30.

FIG. 4 is a cross section taken along line 4-4 of FIG. 1 and depicting further downstream located side-by-side heat sources, at 32 and 34, at a downstream location, such as without limitation following the second roll pass 16, in which the previously heated and initially roll formed sheet is further reconfigured in a targeted or localized fashion so that the bend lines/bend axes are reshaped in the manner shown at 24′/26′ and 28′/30′. The further or second set of heat sources are utilized in order to apply additional targeted heating to one or more selected bend or fold line locations (as previously identified at 24′26′ and 28′/30′ of the intermediate formed article 12″ and prior to the article advancing through the further succeeding roll forming pass 18.

Finally, FIG. 5 is a cross section taken along line 5-5 of FIG. 1, following the final roll pass 18, in which a final cross sectional shape (again at 12′″) is imparted to the linearly fed article (see also further reconfigured bend lines or bend axes at 24″/26″ and 28″/30″ in perpendicular arrangement). This can include an edge trimming and final fabricating step employed to complete the article.

Aspects and benefits of the process and assembly include each of the following:

Refined Microstructure—The strategic addition of heat allows for a localized tempered microstructure that enables Advanced High Strength Materials to be stamped with more complex shapes of varied strengths.

Greater Resistance to Localized Necking—The resulting microstructure is more resistant to localized necking.

Higher Strength—The resulting microstructure is of higher hardness and therefore higher strength.

Greater “Draw-Ability”—Strategic heating allows for more complex shapes of greater depth of draw.

Smaller Radii—Smaller radii are possible with the addition of heat in the process.

Greater Resistance to Edge Fractures—The addition of heat allows material properties with greater resistance to edge fractures.

Lower Forming Tonnages—Elevated temperatures during the forming process lowers the forming forces required to form the same shape with a conventionally stamped product.

Higher Production Rates—With the heating elements being in-line with the Blanking and/or Stamping dies, the production rates are lower than oven heating processes.

Higher Quality Less Spring-Back/Less Sidewall Curl—The heating of the material enables the stamping material to have less spring-back and sidewall curl than conventional stamping processes.

Laser Welded Blank—The heating of a laser welded joint allows for the stress relieves that joint, allowing for greater formability during the forming process.

Having described my invention, other and additional preferred embodiments will become apparent to those skilled in the art to which it pertains, and without deviating from the scope of the appended claims. The detailed description and drawings are further understood to be supportive of the disclosure, the scope of which being defined by the claims. While some of the best modes and other embodiments for carrying out the claimed teachings have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims.

The foregoing disclosure is further understood as not intended to limit the present disclosure to the precise forms or particular fields of use disclosed. As such, it is contemplated that various alternate embodiments and/or modifications to the present disclosure, whether explicitly described or implied herein, are possible in light of the disclosure. Having thus described embodiments of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the present disclosure. Thus, the present disclosure is limited only by the claims.

In the foregoing specification, the disclosure has been described with reference to specific embodiments. However, as one skilled in the art will appreciate, various embodiments disclosed herein can be modified or otherwise implemented in various other ways without departing from the spirit and scope of the disclosure. Accordingly, this description is to be considered as illustrative and is for the purpose of teaching those skilled in the art the manner of making and using various embodiments of the disclosure. It is to be understood that the forms of disclosure herein shown and described are to be taken as representative embodiments. Equivalent elements, materials, processes or steps may be substituted for those representatively illustrated and described herein. Moreover, certain features of the disclosure may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure. Expressions such as “including”, “comprising”, “incorporating”, “consisting of”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Further, various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure. All joinder references (e.g., attached, affixed, coupled, connected, and the like) are only used to aid the reader's understanding of the present disclosure, and may not create limitations, particularly as to the position, orientation, or use of the systems and/or methods disclosed herein. Therefore, joinder references, if any, are to be construed broadly. Moreover, such joinder references do not necessarily infer that two elements are directly connected to each other.

Additionally, all numerical terms, such as, but not limited to, “first”, “second”, “third”, “primary”, “secondary”, “main” or any other ordinary and/or numerical terms, should also be taken only as identifiers, to assist the reader's understanding of the various elements, embodiments, variations and/or modifications of the present disclosure, and may not create any limitations, particularly as to the order, or preference, of any element, embodiment, variation and/or modification relative to, or over, another element, embodiment, variation and/or modification.

It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Additionally, any signal hatches in the drawings/figures should be considered only as exemplary, and not limiting, unless otherwise specifically specified.

Claims

1. A process for heat treating portions of a metal article, comprising the steps: providing a roll of metal;unreeling a continuous sheet of the metal;positioning at least one heating element proximate the sheet prior to a first of a succession of roll pass operations;heating the sheet prior to passing through the first roll pass operation; andbending a cross section of the sheet to exhibit a tighter bend radii.

2. The process as described in claim 1, further comprising advancing the sheet through a second roll pass operation following the first roll pass operation to conduct a further bending operation.

3. The process as described in claim 2, further comprising positioning at least one additional heating element prior to a downstream located roll pass operation performed on the sheet in order to conduct a further bending operation.

4. The process as described in claim 1, said step of positioning the heating elements further comprising locating the heating elements along bend axes of the roll formed article.

5. The process as described in claim 3, further comprising each of a trimming and final fabricating step employed to complete the article.

6. An assembly for forming a metal article, comprising: a coil steel roll is provided for feeding a continuous sheet of said roll through a series of passes corresponding to a series of roll forming operations for progressively shaping the steel sheet between initial planar and finished multi-sided cross sectional shapes;one or more heat elements provided along a travel path of a sheet prior to a first of the roll passes, said heating elements being provided in a linearly arrayed fashion to align with one or more desired bend axes in order to form a finished product from the steel roll;a further heating element located at a downstream location in order to apply additional targeted heating to one or more further selected bend or fold line locations of the article at an intermediate stage; andthe article being advanced through a further succeeding roll forming pass in which a final cross sectional shape is imparted to the linearly fed article to achieve the finished product.

7. The assembly as described in claim 6, further comprising a second roll pass operation following the first roll pass operation for conducting a further bending operation on the continuous fed sheet.

8. The assembly as described in claim 7, further comprising at least one additional heating element positioned at a downstream located roll pass operation performed on the sheet in order to conduct a further bending operation.

9. The assembly as described in claim 6, said at least one additional heating element further comprising a pair of the heating elements located along bend axes of the roll formed article.

10. The assembly as described in claim 8, further comprising each of a trimming and final fabricating step employed to complete the article.