Patent Description:
This application relates to systems and methods for forming a final hollow body from a metal strip, and, more particularly, to roll forming systems and methods for forming a final hollow body from a metal strip.

Certain industries, including but not limited to the automotive industry, may utilize hollow or tubular metal structures for various applications. One method of forming such structures is by extruding a tubular structure and further shaping the tubular structure into a final tubular structure via hydroforming. An alternative method of forming such structures is roll forming a metal sheet followed by seam welding to form a welded tubular structure, and hydroforming the welded tubular structure into the final tubular structure. Traditionally, the integrity of the weld (or seam) of the welded tubular structure has limited the ability of the welded tubular structures to be hydroformed. In particular, roll forming results in significant strain hardening in the material, which adversely affects the material's formability. In addition, seam welding can result in grain refinement based strengthening in the seam region along with the formation of micro-cracks through localized incipient melting and cause a gradient in the strength/hardness profile across the weld. As such, the decreased formability of the weld region, as well as the gradient of the strength/hardness profile across the weld, limit the weld's ability to maintain its integrity during hydroforming.

<CIT> is directed to a method for producing an at least partially hardened profiled component, in which method a semi-finished product, after being heated up to a hardening temperature, is shaped in a forming tool by means of hydroforming or by means of pressing so as to produce the profiled component which, after being shaped in the forming tool, is hardened by means of quenching. <CIT> is directed to a process for forming low cost aluminum alloy hydroforms, in particular low cost hydroformed tubes suitable for assembly as automotive vehicle structures. <CIT> is directed to a method of manufacturing a shaped and hollow structural member via a hydroforming process, comprising the steps of subsequently: providing an extruded or welded tubular or hollow intermediate metal product, placing the intermediate metal product in a die for hydroforming, hydroforming the intermediate metal product to a hydroformed structural member by the introduction of a heated pressure medium having a temperature in the range of <NUM> to <NUM>.

The subject matter of the present invention is defined in the appended claims. According to the invention, a forming system for forming a final hollow body from a metal strip as defined in claim <NUM> includes a forming station, a joining station, an inline heater, and a hydroforming station. The forming station receives the metal strip in a planar configuration and bends the metal strip to a desired cross-section and such that longitudinal edges of the metal strip are abutting. The forming station comprises at least one roller, and the at least one roller may optionally bend the metal strip in a lateral direction. The joining station is downstream from the forming station and welds the abutting longitudinal edges together as a seam region to form an intermediate hollow body. The inline heater is downstream from the joining station and selectively heats at least the seam region of the intermediate hollow body. The hydroforming station is downstream from the inline heater and hydroforms the intermediate hollow body to the final hollow body.

According to the invention, a method of forming a final hollow body from a metal strip as defined in claim <NUM> includes roll forming the metal strip to a desired cross-section and such that longitudinal edges of the metal strip are abutting, and welding the longitudinal edges together as a seam region and to form an intermediate hollow body. The method includes heating at least the seam region of the intermediate hollow body and hydroforming the intermediate hollow body to the final hollow body.

The features and components of the following figures are illustrated to emphasize the general principles of the present disclosure. Corresponding features and components throughout the figures can be designated by matching reference characters for the sake of consistency and clarity.

The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. Directional references such as "up," "down," "top," "bottom," "left," "right," "front," and "back," among others, are intended to refer to the orientation as illustrated and described in the figure (or figures) to which the components and directions are referencing.

All ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of "<NUM> to <NUM>" should be considered to include any and all subranges between (and inclusive of) the minimum value of <NUM> and the maximum value of <NUM>; that is, all subranges beginning with a minimum value of <NUM> or more, e.g. <NUM> to <NUM>, and ending with a maximum value of <NUM> or less, e.g., <NUM> to <NUM>.

Aspects and features of the systems and methods described herein may be used with any suitable metal substrate, and may be especially useful with aluminum or aluminum alloys. Specifically, desirable results can be achieved for alloys such as 1xxx series, 2xxx series, 3xxx series, 4xxx series, 5xxx series, 6xxx series, 7xxx series, or 8xxx series aluminum alloys. For an understanding of the number designation system most commonly used in naming and identifying aluminum and its alloys, see "<NPL>" or "<NPL>.

Described herein are forming systems and methods for forming a final hollow body from a metal strip. The forming system includes a roll forming system that shapes and forms the metal strip from a planar configuration to an intermediate hollow body, and a hydroforming system that shapes the intermediate hollow body to the final hollow body. The roll forming system includes an inline heater that heats at least a seam region of the intermediate hollow body prior to hydroforming. The inline heater may be various suitable devices or combinations of devices for heating at least the seam region. As some non-limiting examples, the inline heater may include one or more of a rotating magnet, an induction inline heater, a gas-powered inline heater, an infrared inline heater, an electric furnace, combinations thereof, or other suitable devices as desired. In some cases, the inline heater may be a rapid inline heater that rapidly heats the intermediate hollow body or portions thereof. In certain aspects, heating at least the seam region of the intermediate hollow body may provide stress relief to the intermediate hollow body and/or may allow for improved control of the distribution of material properties in the seam region (including, but not limited to, homogenizing material properties across the seam region). In some embodiments, heating the intermediate hollow body may soften or decrease the hardness of at least the seam region of the intermediate hollow body prior to hydroforming. Conventional wisdom suggests decreasing the hardness (and thus the strength) of the seam region would be undesirable as this softening would adversely impact the final in-service strength of the material after hydroforming and hence its crash performance. The inventors have discovered that an annealing temperature regime wherein softening from this post weld rapid annealing allows the material to better adapt to and thus withstand to forces that it is subjected to during hydroforming but counter-intuitively, does not impact the final in-service strength of the material in an adverse way. This rapid annealing is an enabler for this sheet tube hydroforming application. In various aspects, the heating from the inline heater may restore some ductility in the metal of the intermediate hollow body, which may improve the integrity of the weld during hydroforming.

<FIG> is a block diagram of a forming system <NUM> according to various embodiments that includes a roll forming system <NUM> and a hydroforming system <NUM>. The roll forming system <NUM> of the forming system <NUM> generally bends a metal strip from a flat or planar configuration into a form of an intermediate hollow body (e.g., a generally tubular form having any cross-section shape as desired). The hydroforming system <NUM> of the forming system <NUM> generally shapes the intermediate hollow body to a final hollow body by using a mold and a highly pressurized fluid on the intermediate hollow body to form the final hollow body.

The roll forming system <NUM> includes a coil feed <NUM>, one or more forming stations <NUM>, a closing station <NUM>, a joining station <NUM>, an inline heater <NUM>, and one or more cooling stations <NUM>. Optionally, the roll forming system <NUM> may include other stations as desired. As a non-limiting example, a cutting station (not shown) may be provided downstream from the cooling station(s) <NUM> to cut the intermediate hollow body into desired lengths.

The coil feed <NUM> of the roll forming system <NUM> supplies an elongated metal strip to the roll forming system <NUM>. In various aspects, the elongated metal strip is provided in coil form, although it need not be in other embodiments. From the coil feed <NUM>, the metal strip is supplied in a generally flat or planar configuration to the forming station(s) <NUM>, which sequentially bend the metal strip from the flat or planar configuration such that longitudinal edges of the metal strip are brought together. Depending on the desired cross-sectional shape of the intermediate hollow body, any desired number of forming stations <NUM> may be utilized, and the forming stations <NUM> may bend the metal strip as desired to achieve the desired cross-sectional shape. In certain embodiments, the forming stations <NUM> may include rollers that sequentially bend the metal strip from the flat or planar configuration, although various other suitable devices for bending the metal strip may be utilized at the forming stations <NUM>.

The closing station <NUM> of the roll forming system <NUM> may further bend the bent metal strip from the forming stations <NUM> such that the longitudinal edges of the bent metal strip are brought into in an abutting and/or overlapping relationship. In certain aspects, the closing station <NUM> includes fin pass rollers and/or other suitable devices for bringing the longitudinal edges into the abutting and/or overlapping relationship. The joining station <NUM> joins the longitudinal edges together via a joining technique to form the intermediate hollow body having a seam region. In various embodiments, the joining station <NUM> includes a welding device, and the longitudinal edges are seam welded together to form the seam region.

The inline heater <NUM> is downstream from the joining station <NUM> and is configured to heat at least the seam region of the intermediate hollow body. The inline heater <NUM> may be various devices or combination of devices suitable for heating at least the seam region, including but not limited to, a rotating magnet, an induction inline heater, a gas-powered inline heater, an infrared inline heater, an electric furnace, combinations thereof, or other suitable devices as desired.

The inline heater <NUM> is controlled by a controller (not shown) communicatively coupled to the inline heater <NUM> such that the inline heater <NUM> heats at least the seam region for a predetermined heating time at a predetermined heating temperature. The predetermined heating time is from greater than <NUM> seconds to <NUM> seconds. In one non-limiting example, the predetermined heating time may be <NUM> seconds. As used, the "predetermined heating time" includes both a ramp up time (e.g., the time it takes to reach the particular temperature) and a dwell time (e.g., the time the metal product is held at the particular temperature). In certain cases, a ramp up time may be <NUM> seconds or less, although in other embodiments the ramp up time may be less than <NUM> seconds or greater than <NUM> seconds. In some cases, the predetermined time may only include a ramp up time and may not include a dwell time. The predetermined heating temperature is greater than or equal to <NUM> to <NUM>, such as from <NUM> to <NUM>, such as from <NUM> to <NUM>, such as from <NUM> to <NUM>, such as about <NUM>. In some non-limiting examples, the inline heater <NUM> is controlled to heat the intermediate hollow body for a predetermined heating time of <NUM> seconds at a predetermined heating temperature of <NUM> to <NUM>. In certain aspects, and as will be discussed in greater detail below with reference to <FIG>, heating the intermediate hollow body with the inline heater <NUM> may allow for stress relief of the material, a decrease in strength, and control of material properties across the seam region, which may improve the integrity of the seam during hydroforming.

In some embodiments, the inline heater <NUM> may be controlled to control at least one of a hardness gradient of the seam region, a residual stress in the seam region, an average hardness of the seam region, or a strength of the seam region. In other embodiments, the inline heater <NUM> may be controlled to control other aspects of the seam region. As will be discussed in greater detail with reference to <FIG> below, in one non-limiting example, the inline heater <NUM> may be controlled such that the residual stress in the seam region is less than about <NUM> MPa, such as less than about <NUM> MPa, although in other embodiments the inline heater <NUM> is controlled such that a residual stress is other suitable values as desired. As will be discussed in greater detail with reference to <FIG> below, in one non-limiting example, the inline heater <NUM> may be controlled such that a yield stress of the seam region is less than <NUM> MPa, such as less than <NUM> MPa, such as less than <NUM> MPa, although in other embodiments, the inline heater <NUM> is controlled such that the yield stress may be other suitable values as desired. As will be discussed in greater detail with reference to <FIG> below, in one non-limiting example, the inline heater <NUM> may be controlled such that a maximum tensile stress of the seam region is less than <NUM> MPa, such as less than <NUM> MPa, such as less than <NUM> MPa, although in other embodiments, the inline heater <NUM> is controlled such that the maximum tensile stress may be other suitable values as desired. In another non-limiting example, and as will be discussed with greater reference to <FIG> below, the inline heater <NUM> may be controlled such that an average hardness of the seam region is less than <NUM> Hv, such as less than <NUM> Hv, although in other embodiments the inline heater <NUM> is controlled such that the seam region has other average hardness values as desired. In a further non-limiting example, and as will be discussed with greater reference to <FIG> below, the inline heater <NUM> may be controlled such that a hardness gradient is reduced and hardness distribution across the seam region is more uniform and homogenized, although in other embodiments the inline heater <NUM> is controlled to provide various hardness gradients as desired. In a non-limiting example, and as will be discussed with greater reference to <FIG> below, the inline heater <NUM> may be controlled such that the yield strength of the seam region is at least <NUM> MPa, although in other embodiments, the inline heater <NUM> may be controlled such that the yield strength of the seam region is other values as desired. The one or more cooling stations <NUM> are downstream from the inline heater <NUM> and are configured to quench the intermediate hollow body. The cooling station(s) <NUM> may be various suitable devices for quenching the intermediate hollow body. In some non-limiting examples, the cooling station(s) <NUM> may be an air cooling device, a water cooling device, combinations thereof, or other suitable devices as desired.

As previously mentioned, the hydroforming system <NUM> of the forming system <NUM> shapes the intermediate hollow body to a final hollow body by using a mold and a highly pressurized fluid on the intermediate hollow body to form the final hollow body. Optionally, the forming system <NUM> may include a pre-bending station prior to the hydroforming system <NUM> for preparing the intermediate hollow body for the hydroforming process.

In various embodiments, a method of forming an intermediate hollow body includes providing a supply of a metal strip at the coil feed <NUM>. In some aspects, the supply of the metal strip is provided in coil form. In various embodiments, the metal strip may be various metal as desired, including but not limited to aluminum, aluminum alloys, steel, or other metals as desired. In one non-limiting example, the metal strip may be a 6xxx series aluminum alloy.

The method includes supplying the metal strip from the coil feed <NUM> to the forming station(s) <NUM>. Supplying the metal strip from the coil feed <NUM> may include supplying the metal strip in a generally flat or planar configuration to the forming station(s) <NUM>. The method includes bending the metal strip with the forming station(s) <NUM> from the flat or planar configuration such that the longitudinal edges of the metal strip are brought together and the metal strip is bent into a desired cross-sectional shape. In certain aspects, bending the metal strip with the forming station(s) <NUM> includes sequentially bending the metal strip with a plurality of rollers such that the longitudinal edges are brought together and the metal strip is bent into the desired cross-sectional shape.

The method includes further bending the bent metal strip with the closing station <NUM> such that the longitudinal edges of the bent metal strip are brought into in an abutting and/or overlapping relationship. In certain aspects, bending the bent metal strip with the closing station <NUM> includes bending the bent metal strip with fin pass rollers and/or other suitable devices for bringing the longitudinal edges into the abutting and/or overlapping relationship. In various embodiments, the method includes joining the longitudinal edges together via a joining technique with the joining station <NUM> to form the intermediate hollow body having a seam region. In certain embodiments, joining the longitudinal edges includes seam welding the longitudinal edges with a welding device to form intermediate hollow body having the seam region.

In various embodiments, the method includes heating at least the seam region of the intermediate hollow body with the inline heater <NUM> and quenching the intermediate hollow body with the cooling station(s) <NUM>. In some embodiments, heating at least the seam region includes heating the intermediate hollow body with a rotating magnet, an induction inline heater, a gas-powered inline heater, an infrared inline heater, an electric furnace, combinations thereof, or other suitable devices as desired. Heating the intermediate hollow body with the inline heater <NUM> includes heating the intermediate hollow body for the predetermined heating time and at the predetermined heating temperature. Heating the intermediate hollow body for the predetermined heating time and at the predetermined heating temperature includes heating the intermediate hollow body with the inline heater <NUM> for a duration of from greater than <NUM> seconds to <NUM> seconds and at a temperature of from greater than or equal to <NUM> to <NUM>. In certain cases, heating the intermediate hollow body with the inline heater <NUM> includes controlling at least one of a hardness gradient of the seam region, a residual stress in the seam region, an average hardness of the seam region, or a strength of the seam region.

The method of forming a final hollow body includes hydroforming the intermediate hollow body with the hydroforming system <NUM>.

<FIG> illustrates a roll forming system <NUM> of a forming system. The roll forming system <NUM> may be substantially similar to the roll forming system <NUM> and includes a coil feed <NUM>, which may be substantially similar to the coil feed <NUM>, the forming stations 208A-D, which may be substantially similar to the forming station(s) <NUM>, a closing station <NUM>, which may be substantially similar to the closing station <NUM>, and the joining station <NUM>, which may be substantially similar to the joining station <NUM>. Similar to the roll forming system <NUM>, the roll forming system <NUM> also includes an inline heater <NUM>, which may be substantially similar to the inline heater <NUM>, and a cooling station <NUM>, which may be substantially similar to the cooling station(s) <NUM>. As illustrated in <FIG>, a metal strip <NUM> is supplied from the coil feed <NUM> in a generally planar or flat configuration. The forming stations 208A-D sequentially bend the metal strip <NUM> from the planar or flat configuration, which is represented in <FIG> by the raised longitudinal edge <NUM> of the metal strip <NUM>. After the longitudinal edge <NUM> is joined with the opposing longitudinal edge (not visible in <FIG>) via the joining station <NUM>, such as by welding, the intermediate hollow body <NUM> is formed, and the intermediate hollow body <NUM> may be heated with the inline heater <NUM> and quenched with the cooling station <NUM>.

<FIG> illustrates an intermediate hollow body <NUM>, which may be substantially similar to the intermediate hollow body <NUM>, and a final hollow body <NUM> after hydroforming by a hydroforming station such as the hydroforming system <NUM>.

<FIG> illustrate non-limiting examples of devices that may be utilized as heaters of a roll forming system of a forming system. Various other types of heaters may be utilized as desired with the roll forming systems described herein.

<FIG> illustrates a heater <NUM> that is a rotating magnet heater and includes a support <NUM> and one or more magnets <NUM> supported on the support <NUM>. In certain aspects, the heater <NUM> may receive an intermediate hollow body within an opening <NUM> of the heater <NUM>, and the heater <NUM> may be rotated round the intermediate hollow body to heat the intermediate hollow body, or the intermediate hollow body may be rotated while the heater <NUM> is held stationary to heat the intermediate hollow body.

<FIG> illustrates a heater <NUM> that is substantially similar to the heater <NUM> and is a rotating magnet heater that includes a support <NUM> and one or more magnets <NUM>. Compared to the heater <NUM>, the arrangement and the number of the magnets <NUM> and the shape of an opening <NUM> of the heater <NUM> are different. Similar to the heater <NUM>, the heater <NUM> may be rotated while the intermediate hollow body is held stationary or vice versa.

<FIG> illustrates a heater <NUM> that is an induction heater having an induction coil <NUM> that may at least partially surround an intermediate hollow body <NUM>.

<FIG> illustrates an example of a cut intermediate hollow body <NUM> formed by a forming system such as the forming system <NUM>. As illustrated in <FIG>, the intermediate hollow body <NUM> has a seam region <NUM> where the longitudinal edges of the metal strip are joined together by the joining station. While the intermediate hollow body <NUM> is illustrated with a circular cross-section, the intermediate hollow body <NUM> may have other shapes as desired depending on the forming station(s) included with the roll forming system.

As mentioned, a forming system with a roll forming system having an inline heater may produce intermediate hollow bodies having improved hydroforming performance. In some cases, heating with the inline heater may reduce the residual stress in a hoop direction at the seam region of the intermediate hollow body compared to intermediate hollow bodies without inline heat treatment (<FIG>). In various cases, heating with the inline heater may improve flaring displacement in the intermediate hollow body compared to intermediate hollow bodies without inline heat treatment (<FIG>). In certain cases, heating with the inline heater may soften the intermediate hollow body compared to intermediate hollow bodies without inline heat treatment (<FIG>). In various embodiments, heating with the inline heater may decrease the hardness of the intermediate hollow body compared to intermediate hollow bodies without inline heat treatment (<FIG>). In some embodiments, heating with the inline heater may surprisingly improve the distribution of hardness across the seam region of the intermediate hollow body compared to intermediate hollow bodies without inline heat treatment (<FIG> and <FIG>).

<FIG> illustrates residual stresses in four samples of intermediate hollow bodies. Each intermediate hollow body is a 6xxx series aluminum alloy and was formed by the same process except for heating with an inline furnace as discussed below. The residual stresses were measured in a hoop direction of each intermediate product (represented by arrows <NUM> in <FIG>). The times / durations provided in <FIG> are all dwell / soaking times (i.e., the duration that each body was held at a particular temperature), and each intermediate body had a ramp up time (i.e., a duration for which the body was heated to reach the particular temperature). For example, a duration shown as "<NUM> seconds" means that the intermediate body was heated during the ramp up time but was not held at the temperature once it was reached, and does not mean that the intermediate body was not heated. The sample intermediate hollow body represented by bar <NUM> was formed without any heating from an inline heater. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The residual stress represented by bar <NUM> was about <NUM> MPa, the residual stress represented by bar <NUM> was about <NUM> MPa, the residual stress represented by bar <NUM> was about <NUM> MPa, and the residual stress represented by bar <NUM> was about <NUM> MPa. As illustrated by comparing bar <NUM> to bars <NUM>-<NUM>, respectively, inline heating reduced the residual stress at the seam regions of the intermediate hollow bodies as the heating temperature increased. The reduction in residual stress provided by the inline heater may improve the formability and the integrity of the seam regions during hydroforming compared to intermediate hollow bodies without inline heating.

<FIG> illustrates flaring displacements in eight samples of intermediate bodies as tested pursuant to a double cone flaring test. The times / durations provided in <FIG> are all dwell times / durations (i.e., the duration that each body was held at a particular temperature), and each intermediate body had a ramp up time (i.e., a duration for which the body was heated to reach the particular temperature). For example, a duration shown as "<NUM> seconds" means that the intermediate body was heated during the ramp up time but was not held at the temperature once it was reached, and does not mean that the intermediate body was not heated. Each intermediate hollow body is a 6xxx series aluminum alloy and was formed by the same process except for heating with an inline furnace as discussed below. The sample intermediate hollow body represented by bar <NUM> was formed without any heating from an inline heater (not according to the invention). The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> minutes (not according to the invention). The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. As illustrated by comparing bar <NUM> with the other bars <NUM>-<NUM>, heating with the inline heater at various combinations of temperatures and durations increased the flaring displacement of the intermediate hollow bodies. In certain aspects, changing the heating temperature had a more significant impact on the flaring displacements compared to changing the heating durations. Compare, for example, the difference between bar <NUM> and bar <NUM>, where the duration was held constant but the heating temperature changed, with the difference between bar <NUM> and bar <NUM>, where the heating temperature was held constant but the heating duration changed.

<FIG> illustrates yield stresses and maximum tensile stresses in five samples of intermediate hollow bodies. Each intermediate hollow body is a 6xxx series aluminum alloy and was formed by the same process except for heating with an inline furnace as discussed below. The times / durations provided in <FIG> are all dwell times (i.e., the duration that each body was held at a particular temperature), and each intermediate body had a ramp up time (i.e., a duration for which the body was heated to reach the particular temperature). For example, a duration shown as "<NUM> seconds" means that the intermediate body was heated during the ramp up time but was not held at the temperature once it was reached, and does not mean that the intermediate body was not heated. The sample intermediate hollow body represented by bars <NUM> and <NUM> was formed without any heating from an inline heater (not according to the invention). The sample intermediate hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> minutes (not according to the invention). The sample intermediate hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample intermediate hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. As illustrated in <FIG>, the heating from the inline heater in general decreased the strength of the intermediate hollow bodies compared to the intermediate hollow body without inline heating, and in general the strength decreased as the heating temperature increased. The decreased strength of the intermediate hollow bodies with the inline heating may surprisingly allow for improved formability and integrity during hydroforming compared to the intermediate hollow body without the inline heating.

<FIG> illustrates the average hardness of seam regions of three samples of intermediate hollow bodies. The times / durations provided in <FIG> are all dwell times (i.e., the duration that each body was held at a particular temperature), and each intermediate body had a ramp up time (i.e., a duration for which the body was heated to reach the particular temperature). For example, a duration shown as "<NUM> seconds" means that the intermediate body was heated during the ramp up time but was not held at the temperature once it was reached, and does not mean that the intermediate body was not heated. Each intermediate hollow body is a 6xxx series aluminum alloy and was formed by the same process except for heating with an inline furnace as discussed below. The sample intermediate hollow body represented by bar <NUM> was formed without inline heating (not according to the invention). The sample represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. The sample represented by bar <NUM> was formed with heating from an inline heater at a temperature of <NUM> and for a duration of <NUM> seconds. As illustrated by comparing bar <NUM> with bars <NUM> and <NUM>, the heating from the inline furnace decreased the average hardness of the seam regions of the intermediate bodies compared to the average hardness of the seam regions of the intermediate body without inline heating. In certain aspects, the decreased average hardness may surprisingly allow for improved formability and integrity during hydroforming compared to the intermediate hollow body without the inline heating.

<FIG> is a hardness heat map of a seam region <NUM> of an intermediate hollow body <NUM> that is a 6xxx series aluminum alloy and was formed without heating from an inline furnace (not according to the invention). In <FIG>, the minimum hardness was <NUM> Hv, the maximum hardness was <NUM> Hv, and the average hardness was <NUM> Hv. <FIG> is a hardness map of a seam region <NUM> of an intermediate hollow body <NUM> that is the same 6xxx series aluminum alloy as the intermediate hollow body <NUM> but was formed with heating from an inline furnace at a temperature of <NUM> and for a dwell duration of <NUM> seconds. In <FIG>, the minimum hardness was <NUM> Hv, the maximum hardness was <NUM> Hv, and the average hardness was <NUM> Hv. As illustrated by comparing <FIG>, the hardness values of the seam region <NUM> (minimum hardness, maximum hardness, and average hardness) were all decreased compared to the corresponding hardness values of the seam region <NUM> (minimum hardness, maximum hardness, and average hardness). Moreover, by comparing the heat distributions, the hardness of the seam region <NUM> was more homogeneous / had a more uniform distribution of hardness across the seam region <NUM> compared to the seam region <NUM>. The decreased hardness and more uniform distribution of hardness provided by the heating with the inline heater may surprisingly allow for improved formability and integrity during hydroforming compared to the intermediate hollow body without the inline heating.

<FIG> illustrates in-service yield strengths and ultimate tensile strengths (i.e., strengths after hydroforming) in five samples of final hollow bodies. Each final hollow body is a 6xxx series aluminum alloy and was formed by the same process except as discussed below. The times / durations provided in <FIG> are all dwell times (i.e., the duration that each body was held at a particular temperature), and each intermediate body had a ramp up time (i.e., a duration for which the body was heated to reach the particular temperature). For example, a duration shown as "<NUM> seconds" means that the intermediate body was heated during the ramp up time but was not held at the temperature once it was reached, and does not mean that the intermediate body was not heated. The sample final hollow body represented by bars <NUM> and <NUM> was formed without any heating from an inline heater (not according to the invention) and was hydroformed without a post form heat treatment or a paint bake. The sample final hollow body represented by bars <NUM> and <NUM> was formed without heating from an inline heater (not according to the invention) but with a post form heat treatment and a paint back prior to hydroforming. The sample final hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline furnace at a temperature of <NUM> and for a duration of <NUM> seconds as well as a post form heat treatment and a paint back prior to hydroforming. The sample final hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline furnace at a temperature of <NUM> and for a duration of <NUM> seconds as well as a post form heat treatment and a paint back prior to hydroforming. The sample final hollow body represented by bars <NUM> and <NUM> was formed with heating from an inline furnace at a temperature of <NUM> and for a duration of <NUM> seconds as well as a post form heat treatment and a paint back prior to hydroforming. In certain embodiments and depending on a particular application for the final hollow bodies, the final hollow bodies may be required to meet certain strength requirements. As one non-limiting example, certain automotive applications may require a yield strength of at least <NUM> MPa. As illustrated in <FIG>, at certain heating temperatures, the final hollow bodies that had the inline heating had in-service strengths that were comparable or better than those that did not have the inline heating and/or were capable of meeting a required yield strength. In other words, the final hollow bodies that had the inline heating were easier to form via hydroforming but still provided comparable or better strengths at certain heating temperatures and/or that could meet performance requirements.

<FIG> illustrates an intermediate hollow body <NUM> formed without heat treatment (not according to the invention), and <FIG> illustrates an intermediate hollow body <NUM> formed by a forming system such as the forming system <NUM>. Both hollow bodies <NUM>, <NUM> were the same 6xxx aluminum alloy, and both were subjected to the same double cone flaring test to produce the flared bodies <NUM>, <NUM> illustrated in <FIG>. Referring to <FIG>, the traditional intermediate hollow body <NUM> achieved a flaring displacement of <NUM> before a crack <NUM> formed on the intermediate body <NUM>, and the crack <NUM> was formed in a weld or seam region <NUM> of the hollow body <NUM>. Referring to <FIG>, the hollow body <NUM> formed using systems and methods described herein by heating the hollow body <NUM> to a temperature of <NUM> during a ramp up time but was not held at that temperature once it was reached. The hollow body <NUM> achieved a flaring displacement of about <NUM> before a crack <NUM> formed on the intermediate body <NUM>, and the crack <NUM> was formed in the parent metal of the intermediate body <NUM> (i.e., a portion of the intermediate body <NUM> other than a weld or seam region <NUM>), and the weld or seam region <NUM> was not cracked. By comparing <FIG> with <FIG>, the intermediate hollow body <NUM> had improved formability and integrity compared to the hollow body <NUM> without the inline heating as represented by the improved flaring performance (<NUM> vs. <NUM>). Moreover, the location of the crack <NUM> in the hollow body <NUM> (i.e., in the parent metal rather than the seam region <NUM>) represents a more homogeneous microstructure and/or homogenous distribution of hardness compared to that of the intermediate body <NUM>.

<FIG> illustrates flaring displacements in five samples of intermediate bodies formed pursuant to methods described herein and a control sample formed without heating (represented by bar <NUM>). All samples were tested pursuant to a double cone flaring test. Each sample was a 6xxx series aluminum alloy and was formed by a forming system. All samples except for the control sample included heating as part of the forming process, and in those samples, the duration that each sample was heated was the same, but the temperature to which each sample was heated was different. In particular: the sample intermediate body represented by bar <NUM> was formed by heating the sample with an inline heater to a temperature of <NUM>; the sample intermediate body represented by bar <NUM> was formed by heating the sample with an inline heater to a temperature of <NUM>; the sample intermediate body represented by bar <NUM> was formed by heating the sample with an inline heater to a temperature of <NUM>; the sample intermediate body represented by bar <NUM> was formed by heating the sample with an inline heater to a temperature of <NUM>; and the sample intermediate body represented by bar <NUM> was formed by heating the sample with an inline heater to a temperature of <NUM>. As mentioned, the sample formed without heating is represented by bar <NUM>.

As illustrated in <FIG>, the sample represented by bar <NUM> had an average flaring displacement of <NUM>; the sample represented by bar <NUM> had an average flaring displacement of <NUM>; the sample represented by bar <NUM> had an average flaring displacement of <NUM>; the sample represented by bar <NUM> had an average flaring displacement of <NUM>; and the sample represented by bar <NUM> had an average flaring displacement of <NUM>. The control sample represented by bar <NUM> had an average flaring displacement of <NUM>. As illustrated, each of the samples formed with heating (e.g., bars <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) exhibited a flaring displacement of greater than that of the control sample (bar <NUM>), and in particular exhibited a flaring displacement that was at least double that of the control sample. The results of <FIG> illustrate the improved formability of the bodies when formed with heating.

<FIG> is a photograph of a microstructure of a seam region <NUM> in a hollow body <NUM> formed according to the methods described herein. The hollow body <NUM> was a 6xxx series aluminum alloy that was formed by heating the sample with an inline heater to a temperature of <NUM> during a ramp up period but was not held at that temperature once reached. As illustrated in <FIG>, the microstructure of the seam region <NUM> is restored to being an almost equiaxed fully recrystallized microstructure compared to the non-seam regions of the hollow body <NUM>, thereby illustrating that the heating according to embodiments of the disclosure produce improved hollow bodies.

<FIG> is a block diagram of another forming system <NUM> according to embodiments. The forming system <NUM> is substantially similar to the forming system <NUM> and includes the roll forming system <NUM> and the hydroforming system <NUM>. Compared to the forming system <NUM>, the forming system <NUM> additionally includes a paint bake system <NUM>. The paint bake system <NUM> may be various suitable systems, devices, and mechanisms for performing a paint bake cycle on hollow body formed by the roll forming system <NUM> and the hydroforming system <NUM>. In certain embodiments, performing a paint bake cycle on the hollow bodies formed by the roll forming system <NUM> and the hydroforming system <NUM> may increase the in-service strength of the hollow bodies compared to both traditionally formed hollow bodies without a paint bake cycle and hollow bodies formed by the roll forming system <NUM> and the hydroforming system <NUM> but without a paint bake cycle. In some embodiments, the paint bake cycle may increase the in-service strength to be closer to a peak yield strength of the alloy forming the hollow bodies compared to hollow bodies formed without the paint bake cycle.

Claim 1:
A forming system (<NUM>) for forming a final hollow body from a metal strip (<NUM>), the forming system (<NUM>) comprising:
a forming station (<NUM>, 208A-D) configured to receive the metal strip (<NUM>) in a planar configuration and bend the metal strip (<NUM>) to a desired cross-section and such that longitudinal edges (<NUM>) of the metal strip (<NUM>) are abutting, wherein the forming station (<NUM>, 208A-D) comprises at least one roller;
a joining station (<NUM>, <NUM>) downstream from the forming station (<NUM>, 208A-D) and configured to weld the abutting longitudinal edges (<NUM>) together as a seam region (<NUM>) and form an intermediate hollow body (<NUM>, <NUM>);
an inline heater (<NUM>, <NUM>) downstream from the joining station (<NUM>, <NUM>) and configured to selectively heat at least the seam region (<NUM>) of the intermediate hollow body (<NUM>, <NUM>);
a hydroforming station (<NUM>) downstream from the inline heater (<NUM>, <NUM>) and configured to hydroform the intermediate hollow body (<NUM>, <NUM>) to the final hollow body (<NUM>),
characterized therein that the forming system (<NUM>) further comprises
a controller communicatively coupled to the inline heater (<NUM>, <NUM>), wherein the controller is configured to control the inline heater (<NUM>, <NUM>) such that the inline heater (<NUM>, <NUM>) heats the intermediate hollow body (<NUM>, <NUM>) at a temperature from <NUM> to <NUM>; and wherein the controller is configured to control the inline heater (<NUM>, <NUM>) such that the inline heater (<NUM>, <NUM>) heats the intermediate hollow body (<NUM>, <NUM>) for a duration of greater than <NUM> seconds to <NUM> seconds.