JP2019073779A - METHOD FOR PRODUCING Al-PLATED STEEL PIPE COMPONENT, AND Al-PLATED STEEL PIPE COMPONENT - Google Patents

Abstract

To provide a method for producing an Al-plated steel pipe component capable of realizing an Al-plated steel pipe component having more excellent flange part corrosion resistance.SOLUTION: Provided is a method for producing an Al-plated steel pipe component comprising: a heating step where an Al-plated steel pipe having an Al-plated layer containing Al and Si is arranged between at least a pair of dies with a prescribed shape, and is heated by conduction heating to a heating temperature within the range from Ac3 transformation point or above to below 1,102°C: a bulging step where air under prescribed pressure is fed to the hollow part of the Al-plated steel pipe whose temperature has been reached to the heating temperature to subject the Al-plated steel pipe to hot blow molding, and a bulged part is formed from the surface of the Al-plated steel pipe; and a molding step where the dies are closed under prescribed pressure, and thereafter air under prescribed pressure is fed to the hollow part of the Al-plated steel pipe to mold a hollow part with a prescribed cross-sectional shape and a flange part projecting from the outer surface of the hollow part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing an Al-plated steel pipe part and an Al-plated steel pipe part.

  In recent years, there has been an increasing demand for suppressing fossil fuel consumption for environmental protection and global warming suppression, and this request affects various manufacturing industries. For example, an automobile that is indispensable for daily life and activities as a means of transportation is no exception, and improvement of fuel consumption by weight reduction of a vehicle body is required. However, in the case of automobiles, merely achieving weight reduction of the vehicle body is not permitted in terms of product quality, and it is necessary to ensure appropriate safety.

  Most of the structures of automobiles are formed of steel materials (particularly steel plates and steel pipes), and reducing the mass of these steel materials is important for reducing the weight of the vehicle body. However, as described above, merely reducing the mass of the steel is not permitted, and it is also required to secure the mechanical strength of the steel. The demand for such steel products is increasing not only in the automobile manufacturing industry but also in various manufacturing industries. Therefore, research and development have been conducted on steel materials that can maintain or increase mechanical strength even if the steel materials are thinner than previously used steel materials by increasing the mechanical strength of the steel materials.

  In general, a steel pipe is characterized in that it is easy to maintain its rigidity with respect to its mass due to its closed cross-sectional shape, which may contribute to weight reduction of various members. However, a steel pipe material having high mechanical strength tends to lower formability and shape freezeability in forming processing such as bending, and when processing into a complicated shape, processing itself becomes difficult. Recently, a method called STAF (Steel Tube Air Forming) (registered trademark) method has been proposed as one of means for solving the problem of the formability of the steel pipe (for example, the following Patent Document 1 and Patent Document 1) See 2). In this STAF method, a steel pipe to be formed is held between molds, and then electrically heated to a high temperature (for example, an austenite region) once, and a gas of a predetermined pressure is supplied to the hollow portion of the steel pipe softened by heating. After blow molding, it cools. According to the STAF method, since the steel pipe is once heated to a high temperature and softened, the steel pipe can be easily blow-processed and, further, the mechanical strength of the steel pipe is enhanced by the hardening effect by cooling after molding. Can. Therefore, it is possible to easily manufacture a hollow member having a flange portion in which good shape freezeability and high mechanical strength are compatible by the STAF method.

  Here, as a technique similar to the STAF method, there is a technique called 3DQ (Three-dimensional hot bending and direct quench) for heating, forming, and quenching a steel pipe. Since 3DQ does not apply internal pressure, pipe expansion / constriction processing is difficult, and while it is difficult to apply a flange, STAF method can perform pipe expansion / condensation processing, and It is also possible to apply a flange. Therefore, the hollow member manufactured by the STAF method has the feature that it becomes easy to join with other parts as a part after that.

JP, 2016-36816, A JP, 2016-12567, A

  When the STAF method as disclosed in Patent Document 1 and Patent Document 2 described above is carried out, for example, in the atmosphere containing oxygen, iron on the surface is oxidized by heating the steel pipe to a high temperature of, for example, 800.degree. Scale (oxide) is generated. Therefore, after applying the STAF method, the process (descaling process) of removing the scale generated on the surface is required, and the productivity is reduced. In addition, in the case of a member requiring corrosion resistance, it is necessary to carry out anticorrosion treatment or metal coating on the surface of the member after processing, and a surface cleaning step and a surface treatment step are required, again reducing the productivity. Furthermore, when shot blasting is used for the purpose of descaling, there is a concern of shape deterioration due to the shot blasting step, and when acid washing is used for the purpose of descaling, the disposal process of the acid treatment liquid Is required.

  In order to suppress such a fall of productivity etc., the present inventors examined covering the surface of the steel pipe provided to the STAF construction method. As an example of such a coating, a zinc-based plating coating having a sacrificial anticorrosion action, which is widely used for automobile steel plates and the like, can be considered. However, the heating temperature (for example, about 800 to 1000 ° C.) in the STAF method may be higher than the decomposition temperature of the organic material or the boiling point of Zn (907 ° C.), and the surface is heated when the material is heated in the STAF method There is a concern that the plating layer of the above may evaporate to cause significant deterioration of the surface properties. Therefore, as a result of further investigations by the present inventors, a steel pipe coated with an Al-based metal having a boiling point higher than that of a Zn-based metal coating for a steel pipe implementing the STAF method of heating to high temperature ( We came to obtain the finding that it is not desirable to use so-called Al-plated steel tubes).

  Here, as a method of manufacturing an Al-plated steel pipe, for example, a method of bending an Al-plated steel plate in which Al plating is applied to both sides of a steel plate, pressing both ends and performing electric resistance welding, A method of forming an Al plating layer on the surface of a steel pipe by dipping in a bath, electroplating using a non-aqueous solution containing aluminum ions, or the like can be considered. An Al plating layer exists on at least the outer surface of the Al-plated steel pipe manufactured by such a method. When such an Al-plated steel pipe is processed by the STAF method to form an Al-plated steel pipe part, the Al plating of the Al-plated steel pipe is alloyed to form an Fe-Al alloy layer.

  On the other hand, among the Al plated steel pipe parts manufactured by the STAF method, the end of the flange portion is subjected to severe processing such as 180 degree 0 T bending, but the flange portion is because the above Fe-Al alloy layer is harder than Al. There is a concern that plating cracking may occur at the end of the iron to expose Fe. If cracking occurs in the plating and Fe is exposed, the corrosion resistance at the end of the flange portion is reduced, and FeO scale grows during high temperature forming by the STAF method, or an Al-plated steel pipe component manufactured is used. The possibility of red rusting is increased.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an Al-plated steel pipe component capable of realizing an Al-plated steel pipe component having better flange portion corrosion resistance. An object of the present invention is to provide a manufacturing method and an Al-plated steel pipe part having a better flange corrosion resistance.

  In order to solve the above problems, as a result of intensive investigations by the present inventors, in the Al-plated steel pipe component manufactured by the STAF method, the generated plating layer is a plating layer mainly composed of a specific alloy phase. It was possible to get the idea that better flange corrosion resistance could be realized.

That is, in order to improve the corrosion resistance of the flange portion, it is considered that the processing to which the plating layer is added should be followed even if the processing for forming the flange portion is added in the STAF method. . On the other hand, an Al plating layer containing Al and Si changes to an Fe-Al based alloy phase when hot blow molded by the STAF method. Therefore, as a result of intensive studies on Fe-Al alloys focusing on ductility at high temperatures, the present inventors (1) among Fe-Al alloys, the alloy phase having the highest ductility at high temperatures is Fe ₂ An alloy phase which has a small temperature dependence of plasticity as compared with (2) Al phase, which is an Al ₅ phase, and a small ductility at high temperatures is the ε phase of a Fe-Al based alloy. I was able to gain knowledge. Based on such findings, the present inventors selectively grow Fe ₂ Al ₅ phase at least at the flange portion and prevent the ε phase from growing, thereby achieving better corrosion resistance of the flange portion. I thought that I could do it.
The summary of the present invention completed based on such findings is as follows.

[1] An Al-plated steel pipe having an Al-plated layer containing Al and Si is disposed between at least one set of molds having a predetermined shape, and then heated within the range of Ac3 transformation point to less than 1102 ° C. By heating to the temperature by electric heating and holding the heating temperature for 1 second to 5 minutes and supplying air of a predetermined pressure to the hollow portion of the Al plated steel pipe which has reached the heating temperature. The Al-plated steel pipe is hot-blow-formed, and an overhanging step of forming an overhanging portion from the surface of the Al-plated steel pipe; and after the mold is clamped at a predetermined pressure, the hollow portion of the Al-plated steel pipe Production of an Al-plated steel pipe part including a forming step of supplying air at a predetermined pressure to form a hollow portion having a predetermined cross-sectional shape and a flange portion protruding from the outer surface of the hollow portion. Method.
[2] A preheating step of preheating an Al-plated steel pipe having an Al plating layer containing Al and Si to a predetermined temperature below 1102 ° C., and at least one set of the preheated Al-plated steel pipe having a predetermined shape And a heating step of heating by heating with current to a heating temperature within the range of Ac3 transformation point to less than 1102 ° C., and a hollow portion of the Al plated steel pipe reaching the heating temperature. The Al-plated steel pipe is hot-blow-formed by supplying air at a predetermined pressure, and an overhanging step of forming an overhanging portion from the surface of the Al-plated steel pipe, and after clamping the mold at a predetermined pressure Forming a hollow portion having a predetermined cross-sectional shape by supplying air at a predetermined pressure to the hollow portion of the Al-plated steel pipe, and forming a hollow portion projecting from the outer surface of the hollow portion; Including, Al steel pipe component manufacturing method.
[3] The coating weight of the Al coating layer is in the range of one face per ^{10g / m 2 ~100g / m 2} , [1] or [2] Al steel pipe component manufacturing method according to.
[4] Any one of [1] to [3], wherein the Al plating layer is an Al-6 to 15 mass% Si plating layer, or a 55 mass% Al-Zn-1.6 mass% Si plating layer The manufacturing method of Al plating steel pipe parts as described in one.
[5] The Al plating layer after the forming step is a plating layer mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al alloy and containing no ε phase of the Fe—Al alloy and Al [5] The manufacturing method of Al plated steel pipe parts as described in any one of 1]-[4].
[6] In the heating step, at least a portion of the Al-plated steel pipe at a position to be the overhanging portion in the overhanging step is electrically heated and electrically heated equipment, and the Al-plated steel pipe at a position not to be the overhanging portion The heating and heating equipment for heating and heating the portion of the portion is separately provided, and the portion of the Al plated steel pipe corresponding to the position to be the overhang portion is heated to a heating temperature within the range of Ac3 transformation point to less than 1102 ° C. The manufacturing method of Al plated steel pipe parts as described in any one of [1]-[4] which heats.
[7] The Al plating layer covering the flange portion after the forming step is mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al based alloy, and the ε phase of the Fe—Al based alloy and Al do not exist The manufacturing method of Al plated steel pipe parts as described in [6] which becomes a plating layer.
[8] The chemical composition of the base steel of the Al-plated steel pipe is, in mass%, C: 0.1 to 0.3%, Si: 0.01 to 0.50%, Mn: 0.5 to 3.0 %, P: 0.003 to 0.050%, S: 0.05% or less, Cr: 0.1 to 0.5%, Ti: 0.01 to 0.10%, Al: 1% or less, B Production of the Al-plated steel pipe component according to any one of [1] to [7], containing 0.0002 to 0.0004%, N: 0.01% or less, and the balance being Fe and impurities Method.
[9] The base steel of the Al-plated steel pipe is replaced with a part of Fe in the remaining part, 1% by mass or less Cu, 2% by mass or less Ni, 1% by mass or less Mo, 1% by mass or less V, And the manufacturing method of Al plated steel pipe parts as described in [8] which further contains at least any one of 1 mass% or less Nb.
[10] A hollow portion having a predetermined cross-sectional shape and a flange portion projecting from the outer surface of the hollow portion are provided at least, and the hollow portion and the flange portion are made of the same steel material as a material and the hollow No joint surface exists between the part and the flange part, and the hollow part and the surface of the flange part are coated with a plating layer mainly composed of an Fe-Al based alloy, The plating layer mainly composed of the Fe-Al based alloy covering the end of the flange portion is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al based alloy, and the ε phase of the Fe-Al based alloy and Al Al-plated steel pipe parts, which is a plating layer that does not exist.
[11] The plating layer mainly composed of the Fe-Al based alloy covering the surface of the hollow part is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al based alloy and the ε phase of the Fe-Al based alloy The Al plated steel pipe part according to [10], which is a plated layer in which Al and Al do not exist.
[12] When the plated layer is measured by an X-ray diffractometer using a Co tube, a peak is observed within the range of the diffraction angle 2θ: 54 ° to 55.3 °, and the diffraction angle 2θ: 40.6 ° the average intensity in the range of to 41 ° and _{I a,} the diffraction angle 2 [Theta]: an average intensity in the range of 58 ° through 59 ° and _{I B,} diffraction angle 2θ: 54 ° ~55.3 peaks in the range of ° The Al-plated steel pipe component according to claim 10, wherein the relationship represented by the following formula (1) is established when the maximum strength is I _C.
[13] The plated layer is measured by an X-ray diffractometer using a Co tube, and the average angle of the diffraction angle 2θ: 34 ° to 35 ° is _ID , and the diffraction angle 2θ: 37 ° to 38 ° Assuming that the average intensity in the range of is I _E and the maximum intensity of the peak in the range of the diffraction angle 2θ: 35 ° to 37 ° is I _F , the relationship represented by the following equation (3) holds The Al plated steel pipe component according to any one of [10] to [12].
[14] the plating layer was measured by X-ray diffraction apparatus using a Co tube, the diffraction angle 2 [Theta]: an average intensity in the range of 43.5 ° ~44.5 ° and _{I G,} the diffraction angle 2 [Theta]: 46 Assuming that the average intensity in the range of degrees to 47 degrees is I _H and the maximum intensity of peaks in the range of diffraction angles 2θ: 44.5 degrees to 45.4 degrees is I _J , the following equation (5) The Al plated steel pipe component according to any one of [10] to [13], in which the represented relationship is established.
[15] The Al-plated steel pipe part according to any one of [10] to [14], which has a continuous deformed closed cross-sectional structure.

  As described above, according to the present invention, it is possible to provide an Al-plated steel pipe part having more excellent flange portion corrosion resistance.

It is the flow chart which showed an example of the flow of the manufacturing method of aluminum plating steel pipe parts concerning the embodiment of the present invention. It is an explanatory view for explaining a manufacturing method of aluminum plating steel pipe parts concerning the embodiment. It is an explanatory view for explaining a manufacturing method of aluminum plating steel pipe parts concerning the embodiment. It is an explanatory view for explaining a manufacturing method of aluminum plating steel pipe parts concerning the embodiment. It is the flowchart which showed another example of the flow of the manufacturing method of Al plating steel pipe parts concerning the embodiment. It is explanatory drawing which showed typically an example of the cross-section of Al plating steel pipe components which concern on the embodiment. It is explanatory drawing which showed typically another example of the cross-section of Al plating steel pipe components which concern on the same embodiment. It is an explanatory diagram for describing _Fe 2 Al ₅ phase of Fe-Al alloy. It is explanatory drawing for demonstrating the epsilon phase of a Fe-Al type alloy. It is explanatory drawing for demonstrating Al which may exist in a plating layer.

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

(About the manufacturing method of Al plating steel pipe parts)
Hereinafter, a method of manufacturing an Al-plated steel pipe part according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.
FIG. 1 is a flow chart showing an example of the flow of a method of manufacturing an Al-plated steel pipe part according to the present embodiment. FIG. 2A to FIG. 2C are explanatory views for explaining the method of manufacturing the Al plated steel pipe part according to the present embodiment. FIG. 3 is a flow chart showing another example of the flow of the method of manufacturing an Al-plated steel pipe part according to the present embodiment.

  In the method of manufacturing an Al-plated steel pipe component according to the present embodiment, the hollow portion and the flange portion are formed by hot blow forming the Al-plated steel pipe as a raw material using the STAF method as exemplified below. It is a method of manufacturing the Al plating steel pipe part which it has.

<About the manufacturing method of Al plating steel pipe>
First, a method of manufacturing an Al-plated steel pipe to be subjected to the STAF method will be described.
The Al-plated steel pipe to be subjected to the STAF method can be manufactured using a known method. For example, after a steel plate having chemical components as described in detail below is subjected to Al plating by a known method to produce an Al-plated steel plate, the obtained Al-plated steel plate is bent and both ends are pressed It can be pipe-made by performing electric resistance welding and can be made into an Al plated steel pipe (more specifically, an Al plated welded pipe). High frequency welding is often used as ERW welding. In general, it is preferable to remove the plating layer at a portion to be a weld bead portion by grinding or the like in advance and then weld. Moreover, in order to flatten a weld bead part after welding, it is preferable to use cutting etc. Furthermore, since the weld bead portion is not coated with plating, surface oxidation during subsequent hot pressing and accompanying decarburization from the surface layer, corrosion during use, and the like may occur. In order to avoid the above possibility, it is preferable to thermally spray a metal containing Al onto the weld bead to form a thermal spray coating on the weld bead. Here, examples of the metal containing Al include pure Al, Al-Zn, Al-Si, Al-Mg and the like. Since Al is excellent in heat resistance, it is excellent in protection during hot pressing. The thickness of the sprayed coating in this case is preferably 5 to 100 μm, for example. Here, thermal spraying shall be performed with respect to a steel pipe outer surface.

  In addition, the Al-plated steel pipe to be subjected to the STAF method uses a known method to apply Al plating to a steel pipe manufactured using a steel ingot having chemical components as described in detail below, or using such a steel ingot It is possible to manufacture by giving Al plating and pipe-making processing with a well-known method with respect to the steel plate manufactured.

  As a base steel of such Al-plated steel pipe, mechanical strength such as tensile strength, yield point, elongation, reduction, hardness, impact value, fatigue strength, creep strength, etc. after processing by the STAF method It is preferable to use a steel material (for example, a high hardenability steel material) designed to have various properties relating to deformation or fracture. An example of the component of the steel material which realizes high mechanical strength that can be used in the present embodiment is as follows.

  The chemical composition of the base steel is, in mass%, C: 0.1 to 0.3%, Si: 0.01 to 0.50%, Mn: 0.5 to 3.0%, P: 0.003 S: 0.05% or less, Cr: 0.1 to 0.5%, Ti: 0.01 to 0.10%, Al: 1% or less, B: 0.0002 to 0.. It is preferable to contain 0004%, N: 0.01% or less, with the balance being Fe and impurities. In addition, such a base steel is replaced with a part of the remaining Fe, 1% by mass or less Cu, 2% by mass or less Ni, 1% by mass or less Mo, 1% by mass or less V, and 1% by mass It may further contain at least one of the following Nb.

  The steel material containing the components as described above is Al-plated and then quenched by electric heating in the STAF method and cooling with a mold to have mechanical strength of about 1500 MPa or more in tensile strength. Thus, although it is a steel material having high mechanical strength, by employing the STAF method, since it is possible to perform blow processing in a state of being softened by electric heating, it can be easily formed. In addition, steel materials can achieve high mechanical strength, and can maintain or improve mechanical strength even if they are thinned for weight reduction.

  On at least the outer surface of a steel pipe using such a base steel, an Al-plated layer containing Al and Si is formed by alloying a steel pipe provided with an aluminum-based plating layer at a temperature of Ac3 or less. ing. The Al plating layer means an alloy plating layer containing various Al alloys containing 50% by mass or more of Al and Si. As this Al plating layer, Al-6-15 mass% Si plating layer or 55 mass% Al-Zn-1.6 mass% Si plating layer can be mentioned, for example. The Al plating layer may be formed by alloying an aluminum-based plating layer formed by hot-dip plating, or may be formed by electroplating.

Deposition amount of the Al plating layer, for example, one face per Al steel pipe is preferably in the range of ^10g / ^{m 2 ~100g} / m 2 at a time prior to subjecting the STAF method. If the adhesion amount of the Al plating layer is less than 10 g / m ² , the corrosion resistance of the manufactured Al plated steel pipe part may not be sufficient, which is not preferable. Moreover, when the adhesion amount of Al plating layer exceeds 100 g / m < ² >, while the corrosion resistance of Al plating steel pipe components is saturated, since the manufacturing cost of Al plating steel pipe components increases, it is unpreferable. In addition, when the adhesion amount of the Al plating layer exceeds 100 g / m ² , when processing the Al-plated steel pipe by the STAF method as described in detail below, a part of the molten Al plating becomes liquid drip, and the STAF method It is not preferable because there is a possibility that it will not be possible to follow processing by Deposition of Al plating layer ^is more preferably in the range of ^{20g / m 2 ~80g / m 2} . In addition, the above-mentioned plating adhesion amount shall also add Fe, Si, etc. which are contained in Al plating layer.

  In addition, a film (surface film layer) mainly composed of ZnO may be applied to the surface of the obtained Al-plated steel pipe in advance. The surface coating layer is laminated on the surface of the Al plating layer. This surface film layer contains at least ZnO. A surface coating layer can be formed by applying and drying this suspension with a roll coater or the like using a liquid in which ZnO fine particles are suspended in an aqueous solution. The presence of such a surface coating layer on the surface of the Al plating layer improves the reactivity with the chemical conversion treatment liquid when various chemical conversion treatments are performed on the manufactured Al plated steel pipe parts (in other words, Coating film adhesion with a chemical conversion film can be improved. Further, such a surface coating layer can improve the lubricity in the STAF method (that is, the lubricity between the Al-plated steel pipe as a material and the mold used in the STAF method).

In the surface film layer, as a component other than ZnO, for example, an organic binder component can be contained. Examples of the organic binder include water-soluble resins such as polyurethane resins, polyester resins, acrylic resins, and silane coupling agents. Moreover, it is also possible to make the surface film layer contain oxides other than ZnO (for example, SiO ₂ , TiO ₂ , Al ₂ O _{3 and the} like).

  As a method of forming a surface film layer containing a binder component as described above, for example, a method of mixing a suspension containing ZnO with a predetermined organic binder and coating it on the surface of an Al plating layer, powder The coating method by coating etc. are mentioned. Moreover, the formation method of a surface film layer is not limited to said example, It can form by well-known various methods.

Adhesion amount of the surface coating layer, one surface per Al steel pipe, the metal Zn, is preferably in the range of ^{0.1g / m 2 ~1g / m 2} . When the adhesion amount of the surface film layer is 0.1 g / m ² or more, the above-described coating film adhesion improving effect, lubricity improving effect, and the like can be exhibited effectively. On the other hand, when the adhesion amount of the surface film layer exceeds 1 g / m 2, the film more than necessary is provided, so that the economic rationality is lacking. In high-strength steel pipe parts used in automobiles etc., since the inner surface of the steel pipe part is unlikely to be exposed to the corrosive environment, it is possible to apply the surface coating layer only to the side that becomes the outer surface of Al-plated steel pipe is there.

<About the manufacturing method of Al plating steel pipe parts by STAF method>
Next, with reference to FIGS. 1 to 2C, a method of manufacturing an Al-plated steel pipe part by the STAF method will be described in detail.
The Al-plated steel pipe part according to the present embodiment is manufactured using, as a raw material, an Al-plated steel pipe, using a forming apparatus suitable for the STAF method as disclosed in, for example, Patent Document 1 or Patent Document 2.

  As shown in FIG. 1, the method of manufacturing an Al-plated steel pipe part by the STAF method includes a heating step (step S101), an overhanging step (step S103), and a forming step (step S105).

  The heating step (step S101) has, as schematically shown in FIG. 2A, the steel pipe 101 having the chemical component as described above, and the Al plating layer 103 as described above located on the steel pipe 101. The Al-plated steel pipe 100 is disposed between at least one set of molds 200 having a predetermined shape (between the upper mold 201 and the lower mold 203 in FIG. 2A), and then has an Ac3 transformation point to less than 1102 ° C. It is a process of heating by electric current heating to a heating temperature within the range and holding the heating temperature for 1 second or more and 5 minutes or less.

  In this heating process, the mold is opened so that the Al-plated steel pipe 100 as a material does not completely adhere to the mold 200, instead of completely closing the mold 200 including the upper mold 201 and the lower mold 203. It is preferable to carry out heating.

By heating the Al-plated steel pipe 100 to a specific heating temperature as described above, the Al-plated steel pipe 100 becomes soft, and the portion in contact with the mold 200 starts to deform and heat is taken away by the mold 200. Partially, cooling starts. In addition, the alloying of the Al plating layer 103 progresses, and the Fe ₂ Al ₅ phase of the Fe—Al alloy is mainly used, and it is changed to a plating layer in which the ε phase of the Fe—Al alloy and Al do not exist. Go.

As mentioned earlier, the Fe ₂ Al ₅ phase of the Fe—Al based alloy is an alloy phase having high ductility at high temperature among various alloy phases of the Fe—Al based alloy. On the other hand, among various alloy phases of the Fe-Al based alloy, the ε (Fe ₂ Al ₃ ) phase is an alloy having a small temperature dependence of plasticity as compared with the Al phase, and a small ductility at high temperature It is a phase. Then, the plating layer (especially plating layer in a flange part) of Al plating steel pipe parts manufactured by the STAF method mainly consists of Fe ₂ Al ₅ phase of Fe-Al based alloy, and does not contain ε phase. By doing this, even when severe processing such as 180 degree 0 T bending is applied in forming the flange portion, it is possible to improve the corrosion resistance of the flange portion without cracking of the plating layer. In addition, when unalloyed Al remains in the plating layer of the Al-plated steel pipe parts, only the portion where the unalloyed Al remains corrodes rapidly, and after coating, coating film swelling is extremely likely to occur in corrosion resistance. Not desirable. Therefore, in the present embodiment, by appropriately controlling the heating temperature in the heating step, the plating layer generated by the STAF method is mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al based alloy, and Fe—Al. It is considered as a plating layer in which ε phase and Al of a base alloy do not exist.

By setting the heating temperature in the heating step to the Ac3 transformation point or more and less than 1102 ° C., it is possible to selectively grow the Fe ₂ Al ₅ phase and obtain the alloy phase not including the ε phase. When the heating temperature is less than the Ac3 transformation point, the Al-plated steel pipe can not be quenched, and it is not possible to manufacture an Al-plated steel pipe part excellent in mechanical strength. Here, although the specific temperature of the Ac3 transformation point depends on the chemical composition of the base steel of the Al-plated steel pipe, it is, for example, in the range of about 700 ° C to 800 ° C. On the other hand, when the heating temperature is 1102 ° C. or more, the ε phase of the Fe—Al alloy selectively grows, and a plating layer mainly composed of the Fe ₂ Al ₅ phase can not be formed. The heating temperature is preferably 900 ° C. or more and 1000 ° C. or less.

In addition, when the holding time of the heating temperature is less than 1 second, unalloyed Al may remain in the plating layer (particularly, the plating layer of the flange portion) of the Al plated steel pipe component manufactured by the STAF method. Unfavorable because of its increased nature. On the other hand, when the holding time exceeds 5 minutes, the Fe ₂ Al ₅ phase decreases due to the progress of Fe diffusion into Al, and the FeAl ₂ phase or FeAl phase inferior in high temperature ductility grows, and flange end face corrosion resistance Unfavorably because it causes deterioration of the The holding time is preferably in the range of 4 seconds to 15 seconds.

  Here, the electric current heating method is not particularly limited, and a known method can be used. Moreover, about the average temperature rising rate to the heating temperature of Ac3 transformation point or more and less than 1102 degreeC, it is preferable to set it as about 50 to 150 degreeC / second, for example.

Here, in the heating process according to the present embodiment, when the heating temperature of the Al-plated steel pipe subjected to the STAF method is set to the Ac3 transformation point or more and less than 1102 ° C. over the entire steel pipe, the entire Al-plated steel pipe component manufactured The component of the plating layer to be coated is mainly a Fe ₂ Al ₅ phase of an Fe—Al alloy, and is a plating layer in which the ε phase of the Fe—Al alloy and Al do not exist.

  However, (a) the Al-plated steel pipe at a position to be an overhang in the overhang step described later (in other words, a portion to be a flange of the Al-plated steel pipe part) as an energization heating facility for energizing and heating the Al-plated steel pipe By separately providing an energization heating facility for energizing and heating a portion and an energization heating facility for energizing and heating a portion of an Al-plated steel pipe at a position which does not become an overhang portion, It becomes possible to separately control the heating temperature and the heating temperature of the portion other than the flange portion. Thereby, the component of the plating layer covering the flange portion of the Al-plated steel pipe component and the component of the plating layer covering the portion other than the flange portion of the Al-plated steel pipe component (that is, the hollow portion) it can.

As mentioned earlier, the severed bending process is applied in the STAF method to the portion to be the flange portion of the Al-plated steel pipe part, so the plating layer is made of Fe ₂ Al ₅ phase of Fe—Al based alloy It is necessary to use a plated layer mainly composed of an ε-phase of an Fe—Al based alloy and without Al. On the other hand, it is also possible to add another function to the plating layer other than the flange portion by growing another alloy phase of the Fe-Al based alloy as the plating layer other than the flange portion.

For example, although the ε phase of Fe-Al alloys is inferior to the Fe ₂ Al ₅ phase in terms of ductility at high temperatures, the ε phase is compared with other alloy phases including the Fe ₂ Al ₅ phase, Since it is a relatively soft alloy phase, it is possible to improve the wear resistance after processing by growing the ε phase of the Fe—Al based alloy as the plating layer. The ε phase can be selectively grown by setting the heating temperature to 1102 ° C. or more and 1232 ° C. or less.

  In the overhanging step (step S103), as schematically shown in FIG. 2B, the air pressure is prevented from dropping off the hollow portion of the Al-plated steel pipe 100 which has reached the desired heating temperature, and then the predetermined pressure is obtained. The aluminum-plated steel pipe 100 is hot-blow-formed by supplying air. Also in the overhanging process, air having a predetermined pressure is supplied without closing the mold 200. As a result, the Al-plated steel pipe 100 is deformed by the high pressure air supplied to the hollow portion, and the overhang portion 105 as schematically shown in FIG. 2B is formed. Here, the pressure of air supplied to the hollow portion of the Al-plated steel pipe 100 is preferably about 15 MPa to 17 MPa.

  The overhanging process is continued until the size of the overhanging portion 105 becomes the flange width required for the Al-plated steel pipe component which is a product.

  In the forming step (step S103), as schematically shown in FIG. 2C, after the mold 200 is clamped at a predetermined pressure, air at a predetermined pressure is supplied to the hollow portion of the steel pipe to make the predetermined This is a step of forming the hollow portion 3 having a cross-sectional shape and the flange portion 5 projecting from the outer surface of the hollow portion 3. Here, the pressure of the air supplied to the hollow portion of the steel pipe is preferably a pressure higher than the pressure of the air supplied in the extension step, and for example, preferably 20 MPa to 40 MPa.

  By supplying the high pressure air as described above, the Al-plated steel pipe 100 comes in close contact with the mold 200 completely clamped, and the Al is formed into a shape defined by the upper mold 201 and the lower mold 203. The plated steel pipe is deformed. Thereby, the Al plated steel pipe part 1 having the hollow portion 3 and the flange portion 5 is manufactured. Here, the steel material 11 of the Al-plated steel pipe component 1 manufactured is derived from the steel pipe 101 of the Al-plated steel pipe 100, and the plating layer 13 of the Al-plated steel pipe component 1 mainly includes the ε phase of Fe-Al based alloy It becomes a plating layer.

  Here, in the overhanging step and the forming step, the cooling rate (average cooling rate) by the mold 200 is preferably, for example, 20 ° C./second or more. Such a cooling rate is an important condition in order to obtain a high strength member by quenching. Although the upper limit value of the cooling rate is not particularly limited, it is difficult in practice to set it to 300 ° C./second or more. The cooling rate of the quenching by the mold is more preferably 30 ° C./s or more and 300 ° C./s or less.

  In order to further improve the lubricity between the manufactured Al-plated steel pipe part 1 and the mold 200 in the upper mold 201 and the lower mold 203 used in the STAF method, the upper mold 201 and the lower mold 203 are used. A film mainly composed of ZnO may be formed on the portion in contact with the Al-plated steel pipe.

<On the variation of the manufacturing method of Al plated steel pipe parts by STAF method>
Next, with reference to FIG. 3, a modification of the method of manufacturing an Al-plated steel pipe part by the STAF method will be briefly described.
In the method of manufacturing Al-plated steel pipe parts by the STAF method described earlier, the Al-plated steel pipe can be quenched by electric heating from the beginning, and Fe ₂ Al ₅ phase of Fe—Al alloy is generated, and It was heated to a temperature range where ε phase is not generated, and was maintained for a predetermined time. However, even if the method described below is used, a plated layer mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al alloy and having no ε phase and Al of the Fe—Al alloy is formed. Can.

  That is, as shown in FIG. 3, in the method of manufacturing an Al-plated steel pipe part according to the present modification, the preheating step (step S111), the heating step (step S113), the overhanging step (step S115), and the forming And (step S117).

  The preheating step (step S111) preheats the Al-plated steel pipe having the above-described steel pipe having the chemical components and the above-described Al-plated layer located on the steel pipe to a predetermined temperature less than 1102 ° C. Process. Here, the preheating method of the Al-plated steel pipe is not particularly limited, and a method of heating by passing the Al-plated steel pipe into a furnace maintained at a high temperature such as an electric furnace, a near infrared heating furnace, high frequency A well-known heating method, such as a method using heating and electric current heating, can be used. By preheating the Al-plated steel pipe to a temperature less than 1102 ° C., it is possible to reduce the possibility that the Al-plated layer adheres to the mold 200. In addition, by providing such a preheating step, it is possible to shorten the holding time or to set the holding time to zero in the heating step performed in the latter stage. Alternatively, after the preheating step, the product may be temporarily cooled to room temperature and stored, and then transferred to the subsequent heating step.

  In the preheating step, the preheating temperature of the Al-plated steel pipe is preferably, for example, in the range of 700 ° C. to 900 ° C.

  In the heating step (step S113) performed after the preheating step, the preheated Al-plated steel pipe is disposed between at least one set of molds having a predetermined shape, and then the Ac3 transformation point to less than 1102 ° C. It is the process of heating by electric current heating to the heating temperature within the range. Here, in the heating process according to this modification, the heating shown in FIG. 1 and FIG. 2A as described above, except that the holding time of the heating temperature not lower than the Ac3 transformation point and lower than 1102 ° C. is specified in particular. The process is similar to that of the process and has the same effect, so the detailed description is omitted below.

  In addition, the overhanging process (step S115) and the forming process (step S117) performed after the heating process (step S113) are also the overhanging process shown in FIG. 1, FIG. 2B and FIG. 2C as described earlier The process is similar to the forming process and has the same effect, so the detailed description is omitted below.

As described above, in the method of manufacturing an Al-plated steel pipe component according to this embodiment, the Fe-plated steel pipe on which the Al-plated layer is formed is heated to a specific temperature range of Ac3 transformation point to less than 1102 ° C. composed mainly of _Fe 2 Al ₅ phase -Al alloy and no ε phase and Al Fe-Al alloy to produce a particular alloy phases. Thereby, the corrosion resistance of the flange portion can be improved.

(About Al-plated steel pipe parts)
Next, with reference to FIGS. 4A to 7, Al-plated steel pipe parts manufactured by the STAF method as described above will be described in detail. FIG. 4A is an explanatory view schematically showing an example of the cross-sectional structure of the Al plated steel pipe part according to the present embodiment, and FIG. 4B is another example of the cross sectional structure of the Al plated steel pipe part according to the present embodiment. It is explanatory drawing shown typically. FIG. 5 is an explanatory view for explaining an Fe ₂ Al ₅ phase of the Fe-Al based alloy, and FIG. 6 is an explanatory view for explaining an ε phase of the Fe-Al based alloy, FIG. These are explanatory drawings for demonstrating Al which may exist in a plating layer.

<About the whole structure of Al plated steel pipe parts>
The Al-plated steel pipe part 1 according to the present embodiment is manufactured by forming the Al-plated steel pipe using the Al-plated steel pipe as a material by the STAF method as described above. This Al plated steel pipe part 1 has a hollow portion 3 and a flange portion 5 as schematically shown in FIG. 4A.

  The hollow portion 3 has a predetermined cross-sectional shape. Here, the cross-sectional shape in the hollow portion 3 is not particularly limited, and may be a rectangular shape as shown in FIG. 4A, a circular shape, an elliptical shape, a polygonal shape, etc. It may be of various types. The cross-sectional shape of the hollow portion 3 depends on the shape of the mold used in the STAF method, and the cross-sectional shape of the hollow portion 3 can be adjusted by setting the shape of the mold to a desired shape.

  The flange portion 5 is provided to protrude from the outer surface of the hollow portion 3. Here, the number of flanges 5 and the position at which the flanges 5 are provided in the Al plated steel pipe part 1 according to the present embodiment are not particularly limited, and one or more arbitrary number of flanges 5 can be provided at any position of the hollow portion 3. Further, the shape of the flange portion 5 is not limited to the example shown in FIG. 4A, and can be any shape. The shape, number, and installation position of the flange portion 5 also depend on the shape of the mold used in the STAF method, and the shape, number, and installation position of the flange portion 5 can be obtained by making the shape of the mold into a desired shape. Etc can be adjusted.

  The hollow portion 3 and the flange portion 5 are made of the same steel material 11 and, as schematically shown in FIG. 4A, there is no joint surface between the hollow portion 3 and the flange portion 5, It is integrated. Such an integrated structure is realized by hot-blow molding an Al-plated steel pipe, which is a raw material, by the STAF method.

Moreover, in the Al plated steel pipe part 1 according to the present embodiment, the entire surfaces of the hollow portion 3 and the flange portion 5 are covered with the plating layer 13. Of the plating layer 13, the plating layer covering at least the end of the flange portion 5 is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al alloy, and the ε phase of the Fe-Al alloy and Al are present. It is not a plating layer. Further, the plated layer mainly composed of Fe ₂ Al ₅ phase and not containing ε phase of Fe-Al alloy and Al may cover the whole of the flange portion 5, and the hollow portion 3 and the flange portion The whole of 5 may be covered.

In addition, the plating layer 13 other than the end of the flange portion 5 is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al alloy as described above, and the ε phase of the Fe-Al alloy and Al do not exist. Other than the layer, it may be a plating layer containing an Fe-Al based alloy (for example, ε phase etc.).

  Such division of the plating layer in the flange portion 5 and the plating layer in portions other than the flange portion 5 is realized by appropriately controlling the heating temperature in the heating step of the STAF method as described above. can do.

Here, whether or not the Fe ₂ Al ₅ phase is the main component in the plating layer 13 can be confirmed by measuring the plating layer 13 with an X-ray diffractometer using a Co tube.

In such a case, first, the plating layer 13 is measured by an X-ray diffraction apparatus using a Co tube to obtain an X-ray diffraction spectrum. When the Fe ₂ Al ₅ phase is present in the plating layer 13, the obtained X-ray diffraction spectrum belongs to the Fe ₂ Al ₅ phase in the range corresponding to the diffraction angle 2θ = 54 ° to 55.3 °. Characteristic peaks are observed. Therefore, the presence of the Fe ₂ Al ₅ phase can be confirmed by the presence or absence of such a peak.

Then, as schematically shown in FIG. 5, by analyzing the X-ray diffraction spectrum obtained, the diffraction angle 2 [Theta]: 40.6 ° to 41 and the average intensity I _A ranging °, diffraction angle 2 [Theta]: and average intensity _{I B} in the range of 58 ° through 59 °, to identify. Further, it attributed to _Fe 2 Al ₅ phase, the diffraction angle 2θ: 54 ° ~55.3 identifying the maximum intensity _{I C} of the peak in the range of °. Then, when the following equation (101) is satisfied, it can be determined that the Fe ₂ Al ₅ phase of the Fe—Al alloy is mainly present in the plating layer 13.

Here, the denominator on the left side of the above equation (101) gives the average baseline intensity of the X-ray diffraction spectrum within the range of the diffraction angle 2θ of 40.6 ° to 59 °. Therefore, in the case where the maximum peak intensity of the peak observed in the range of the diffraction angle 2θ: 54 ° to 55.3 ° exceeds five times the average baseline intensity, the above equation (101) is in the plating layer 13 , It can be judged that the Fe ₂ Al ₅ phase is the main component.

  In addition, whether or not the ε phase of the Fe-Al based alloy is present in the plating layer 13 is similarly confirmed by measuring the plating layer 13 with an X-ray diffractometer using a Co tube. be able to.

  In such a case, first, the plating layer 13 is measured by an X-ray diffraction apparatus using a Co tube to obtain an X-ray diffraction spectrum. When the ε phase of the Fe—Al alloy is present in the plating layer 13, the characteristic belonging to the ε phase is in the range corresponding to the diffraction angle 2θ = 35 ° to 37 ° in the obtained X-ray diffraction spectrum Peak is observed. Therefore, the presence of the ε phase can be confirmed by the presence or absence of such a peak.

Subsequently, as schematically shown in FIG. 6, the obtained X-ray diffraction spectrum is analyzed, and the diffraction angle 2θ: average intensity _{ID in} the range of 34 ° to 35 ° and the diffraction angle 2θ: 37 ° Identify an average intensity _{IE in} the range of -38 °. Moreover, the maximum intensity I _F of the peak within the range of the diffraction angle 2θ: 35 ° to 37 °, which is attributed to the ε phase of the Fe—Al based alloy, is specified. In addition, it can be determined that the ε phase of the Fe—Al alloy does not exist in the plating layer 13 when the following equation (103) is established.

  Here, the denominator on the left side of the above equation (103) gives the average baseline intensity of the X-ray diffraction spectrum within the range of the diffraction angle 2θ of 34 ° to 38 °. Therefore, the above equation (103) indicates that the Fe in the plating layer 13 is present when the maximum peak intensity of the peaks observed within the range of the diffraction angle 2θ: 35 ° to 37 ° is 8 times or less of the average baseline intensity. -Shows that it can be judged that the ε phase of the Al-based alloy does not exist.

  Furthermore, whether or not Al is present in the plating layer 13 can be similarly confirmed by measuring the plating layer 13 with an X-ray diffractometer using a Co tube.

  In such a case, first, the plating layer 13 is measured by an X-ray diffraction apparatus using a Co tube to obtain an X-ray diffraction spectrum. When Al is present in the plating layer 13, a characteristic peak belonging to Al is observed in the range corresponding to the diffraction angle 2θ = 44.5 ° -45.4 ° in the obtained X-ray diffraction spectrum Be done. Therefore, the presence of Al can be confirmed by the presence or absence of such a peak.

Then, as schematically shown in FIG. 7, by analyzing the obtained X-ray diffraction spectrum, the diffraction angle 2 [Theta]: the average intensity I _G in the range of 43.5 ° ~44.5 °, diffraction angle 2θ: The average intensity I _{H in} the range of 46 ° to 47 ° is specified. Moreover, the maximum intensity I _J of the peak within the range of the diffraction angle 2θ: 44.5 ° to 45.4 °, which is attributed to Al, is specified. Then, it is possible to determine that Al does not exist in the plating layer 13 when the following equation (105) is established.

  Here, the denominator on the left side of the above equation (105) gives the average baseline intensity of the X-ray diffraction spectrum within the range of the diffraction angle 2θ of 43.5 ° to 47 °. Therefore, the above equation (105) indicates that the plating layer is formed when the maximum peak intensity of peaks observed within the range of diffraction angle 2θ: 44.5 ° to 45.4 ° is 5 times or less of the average baseline intensity It shows that it can be judged that Al does not exist in No. 13.

Therefore, when the plating layer 13 is a plating layer mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al alloy and the ε phase and Al of the Fe—Al alloy do not exist, the above formula (101), 103) and equation (105) will be satisfied simultaneously.

Coating weight mainly composed of Al in Al steel pipe before subjecting the STAF method ^is in the range of ^{10g / m 2 ~100g / m 2} . In this plating, the plating layer 13 becomes a plating layer mainly composed of an Fe ₂ Al ₅ phase (mass ratio Fe 45: Al 55) by an alloying reaction caused by diffusion of Fe from the steel material accompanying the heat treatment of the STAF method. adhesion amount including Al-based alloy is about twice that of ^20g / ^{m 2 ~200g} / m 2 of the original coating weight. When the adhesion amount of the plating layer 13 is less than 20 g / m ² , the corrosion resistance of the Al-plated steel pipe part 1 may not be sufficient, which is not preferable. When the adhesion amount of the plating layer 13 exceeds 200 g / m ² , the corrosion resistance of the Al-plated steel pipe part 1 is saturated, while the manufacturing cost of the Al-plated steel pipe part 1 is increased. Coating weight of the plating layer 13 ^is more preferably in the range of ^{20g / m 2 ~160g / m 2} . In addition, Fe, Si, etc. which are contained in the plating layer 13 shall be added by the spreading | diffusion from the steel materials accompanying the heat processing of the STAF method, etc. of the adhesion amount of said plating layer 13. FIG. Therefore, the Fe-Al based alloy generated in the heat treatment in the STAF method is included in the plating adhesion amount.

  In the Al-plated steel pipe part 1 having a layered structure as described above, both of the hollow portion 3 and the flange portion 5 are formed by continuous steel plates 11 and the plating layer 13 which are continuous (without a joint surface). It has a cross-sectional structure.

  In the example shown in FIG. 4A, the external shape of the hollow portion 3 and the flange portion 5 is a straight line in the example shown in FIG. 4A, but the external shape of the Al-plated steel pipe component 1 is a curved line. And may be composed of both straight lines and curves. Moreover, the corner | angular part (corner part) of the hollow part 3 and the flange part 5 may have R shape.

  Further, although the example shown in FIG. 4A shows the case where the plating layer 13 is present on both the outer surface and the inner surface of the steel material 11, for example, as shown in FIG. It may exist only on either the outer surface side or the inner surface side of Regarding whether the plating layer 13 exists only on one side of the steel material 11 or on both surfaces of the steel material 11, the Al plating layer of the Al-plated steel pipe used as the material of the Al-plated steel pipe part 1 It depends on the adhesion state.

  In the Al plated steel pipe part 1 according to this embodiment as shown in FIGS. 4A and 4B, a film mainly composed of ZnO (that is, a surface film layer, not shown) on the surface of the plating layer 13. May be formed. The film mainly composed of ZnO may be formed on the plating layer 13 after the Al-plated steel pipe part 1 according to the present embodiment is manufactured by applying the STAF method to the Al-plated steel pipe which is a material. It is also possible to form a film mainly composed of ZnO on the surface of an Al-plated steel pipe, which is a raw material, and then apply the STAF method to the Al-plated steel pipe. The presence of a coating mainly composed of ZnO on the surface of the plating layer 13 improves the reactivity with the chemical conversion treatment liquid when performing various chemical conversion treatments on the Al-plated steel pipe part 1 (in other words, Coating film adhesion with a chemical conversion film can be improved.

Coating weight of a film composed mainly of such ZnO is per side of Al steel pipe part 1, as the metal Zn, is preferably in the range of ^{0.1g / m 2 ~1g / m 2} . When the adhesion amount of the film mainly composed of ZnO is 0.1 g / m ² or more, the above-described coating film adhesion improving effect can be effectively exhibited. On the other hand, when the adhesion amount of the film mainly composed of ZnO exceeds 1 g / m 2, the film more than necessary is provided, so that the economic rationality is lacking. In the high strength steel pipe parts used for automobiles etc., the inner surface of the steel pipe parts is unlikely to be exposed to the corrosive environment, so it is possible to apply a film mainly composed of ZnO only to the outer surface of the steel 11. It is possible.

  The overall structure of the Al-plated steel pipe component 1 according to the present embodiment has been described above with reference to FIGS. 4A and 4B.

  Hereinafter, the method for producing an Al-plated steel pipe component and the Al-plated steel pipe component according to the present invention will be specifically described while showing experimental examples. The experimental examples shown below are merely examples of the method for producing an Al-plated steel pipe component according to the present invention and the Al-plated steel pipe component, and the method for producing an Al-plated steel pipe component according to the present invention and the Al-plated steel pipe component It is not limited to the example of.

  First, as a chemical composition, C: 0.2%, Si: 0.2%, Mn: 1.3%, P: 0.013%, S: 0.003%, Cr: 0.2% by mass as mass%. %, Al: 0.040%, B: 0.0014%, Ti: 0.02%, N: 0.003%, with the balance being Fe and impurities The steel slab is conventionally hot rolled, By pickling and cold rolling, a 2.0 mm thick cold rolled steel plate (full hard plate) was manufactured. The Ac3 point of this component is 789 ° C. The obtained cold rolled steel sheet is subjected to reduction annealing according to a conventional method in a continuous plating line, and then Al-6 mass% Si plating, Al-9 mass% Si plating, Al-12 mass% Si plating, Apply Al-15% by mass Si plating or Zn-55% Al-1.6% Si (gallium, hereinafter abbreviated as “GL”) plating, adjust the amount of adhesion by gas wiping, and It cooled. In addition, a non-plated steel plate was also prepared for comparison. These steel plates thus obtained were formed into electric resistance welded steel pipes by a conventional method. The dimension of the ERW welded steel pipe was 50.8 mm in outer diameter.

  A mixture of ZnO, urethane resin emulsion, and silane coupling crosslinker with an average particle diameter of 70 nm is applied to a part of the obtained ERW welded steel pipe with a plating coater, and at about 80 ° C. I burned it.

  The ERW-welded steel pipe thus obtained was cut into a circle with a length of 400 mm, subjected to the subsequent test process, and an Al-plated steel pipe part was manufactured by the STAF method shown in FIG. 1 or FIG.

  In the heating process in the STAF method, the average temperature rising rate by electric heating and the holding time were changed for each test. Details of the average temperature rising rate and the holding time are as shown in Table 1 below. Further, the preheating step in the STAF method shown in FIG. 3 is performed by holding the electric muffle furnace in the atmosphere at 900 ° C., holding the collected pipe in the furnace for 5 minutes, taking out in the air and leaving it to cool. The The cooling was all performed by contact cooling with the mold, and the measured value by the thermocouple welded to the inside of the tube was a cooling rate of 80.degree. C./sec on average from the maximum temperature to 200.degree. The pressure of air supplied in the overhanging step was 15 MPa, and the pressure of air supplied in the forming step was 25 MPa.

  The dimension after molding (ie, the dimension of Al-plated steel pipe parts) is a square of 32 mm × 22 mm, and a shape in which a 15 mm long flange extends vertically from the center of each of two 22 mm sides A shape similar to the shape shown in 4A).

  For each Al-plated steel pipe part having a flange obtained as described above, a test piece of 10 mm square was collected from the flange portion, and X-ray diffraction measurement was performed using a SmartLab manufactured by Rigaku Corporation as a measurement device. The tube used Co. From the obtained profiles of the diffraction angle 2θ and the diffraction intensity, the values of Formula (101), Formula (103) and Formula (105) were calculated according to the method described above.

  Moreover, about each Al plated steel pipe part obtained as mentioned above, evaluation was performed from a viewpoint of the presence or absence of Fe scale, weld joint strength, wear resistance, and corrosion resistance.

(With or without Fe scale)
The presence or absence of the Fe scale was evaluated by visually observing the appearance after the test. If the Fe scale was generated, it was "NG", and if it was not generated, it was "OK".

(Flange end corrosion resistance)
The prepared material was cut into a length of 150 mm and then cut axially along the middle of the non-flanged side (i.e., left and right in FIG. 4A). After forming a chemical conversion treatment using PB-SX35T manufactured by Nihon Parkerizing Co., Ltd., electrodeposition coating was applied to aim a film thickness of 20 μm using Powernix 110 manufactured by Nippon Paint Co., Ltd. and baked at 170 ° C. Then, it cut with the cutter knife along the flange end. At the time of cutting, a jig was produced so that the cut did not come off the flange end. Fix the test piece so that the flange points up in the corrosion tester, carry out the corrosion test specified in JASO M 609 for 180 cycles = 60 days, and evaluate the swelling width of the coating film with the maximum value on one side The flange end corrosion resistance was evaluated.

  The obtained results are summarized in Table 1 below.

No. 1 is a state before forming the Al-9% Si plating at a deposition amount of 70 g / m ² , without applying ZnO or preheating, and before being subjected to the STAF process. At this time, neither the ε phase nor the Fe ₂ Al ₅ phase was detected in the plating film, and only the Al phase was detected.

No. No.2-6 formed Al-9% Si plating by adhesion amount 70g / m ² , there was neither ZnO application nor preheating, average heating rate was made into one condition of 150 ° C / s, maximum heating temperature is 910-1300. It was changed in the range of ° C., and the holding time was 0.1 second. When the maximum heating temperature is in the range of Ac 3 to 1102 ° C., the Al phase remains in the plating layer, and at the maximum heating temperature of 1102 ° C. or more, the ε phase is generated in the plating layer. It turns out that corrosion resistance is inferior. It can be seen that at a holding time of 0.1 second there is no adequate temperature range.

No. For 7 to 10, Al-9% Si plating is formed at a deposition amount of 70 g / m ² , ZnO coating is neither applied nor preheated, the temperature is raised at an average temperature rising rate of 30 ° C./sec, and the maximum heating temperature is 800 ° C. The holding time is changed in the range of 0 to 500 seconds. When the holding time is 0 seconds, the Al phase remains in the plating layer and the flange end surface corrosion resistance is inferior, but when the holding time is 10 to 50 seconds, the Al phase does not remain in the plating layer It can be seen that the Fe ₂ Al ₅ phase is formed to improve the flange end corrosion resistance. However, when the holding time is 500 seconds, it can be seen that the Fe ₂ Al ₅ phase is not present, and the flange end corrosion resistance is deteriorated. From these results, it can be seen that there is an appropriate range for the holding time.

No. 11-15 form Al-9% Si plating with a deposition amount of 70 g / m ² , no ZnO coating and no preheating, raise the temperature at an average heating rate of 30 ° C./sec, and maintain at a maximum heating temperature of 1000 ° C. The time is changed in the range of 0 to 350 seconds. When the holding time is 0 seconds, the Al phase remains in the plating layer and the flange end surface corrosion resistance is inferior, but when the holding time is 1 to 40 seconds, the Al phase does not remain and Fe ₂ Al ₅ It can be seen that a phase is formed to improve the flange end surface corrosion resistance. However, when the holding time is 350 seconds, it can be seen that the Fe ₂ Al ₅ phase disappears and the flange end corrosion resistance is degraded. From these results, it can be seen that there is an appropriate range for the holding time.

No. 16, 17 and 12 form an Al-9% Si plating at a deposition amount of 70 g / m ² , with neither ZnO coating nor preheating, raising the temperature at an average temperature increase rate of 30 ° C./s, and the maximum heating temperature of 1000 to 1000 It was held for 1 second while changing in the range of 1080 ° C. In any case, it is understood that the plated layer is mainly composed of the Fe ₂ Al ₅ phase and there is neither ε phase nor Al phase, and the flange end surface is excellent in corrosion resistance.

No. No. 18 formed GL (Zn-55% Al-1.6% Si) plating by the adhesion amount 70g / m < ² >, there is neither ZnO application nor a preheat, and it is a state before using for a STAF process. At this time, neither the ε phase nor the Fe ₂ Al ₅ phase was detected in the plating film, and only the Al phase was detected.

No. For 19 to 22, the GL plating is formed at an adhesion amount of 70 g / m ² , no ZnO coating or preheating, the temperature is raised at an average heating rate of 150 ° C./sec, and the maximum heating temperature changes in the range of 910 to 1300 ° C. The holding time is 0.1 second. When the maximum heating temperature is 910 ° C., it is understood that the Al phase remains in the plating layer and the flange end surface corrosion resistance is inferior. When the maximum heating temperature is 1110 to 1200 ° C., the ε phase is generated in the plating layer, and when the maximum heating temperature is 1200 to 1300 ° C., the Fe ₂ Al ₅ phase does not exist in the plating layer In either case, it is understood that the flange end surface corrosion resistance is inferior. From these results, it can be seen that the proper temperature range does not exist at a retention time of 0.1 seconds.

No. 23 to 26 heats GL plated steel at an average heating rate of 30 ° C./sec and changes the maximum heating temperature in the range of 800 to 1000 ° C. and changes the holding time in the range of 0 to 5 seconds It is. When the holding time is 0 seconds, it is understood that the Al phase remains in the plating layer and the flange end surface corrosion resistance is inferior even when the maximum heating temperature is either 800 ° C. or 1000 ° C. When the holding time is 5 seconds, it can be seen that the plated layer is mainly composed of the Fe ₂ Al ₅ phase and excellent in flange end surface corrosion resistance, regardless of the maximum heating temperature of either 800 ° C. or 1000 ° C. From these results, the appropriate range of the holding time and the maximum heating temperature can be known.

No. No.27 to 31 form Al-9% Si plating at a deposition amount of 70 g / m ² , preheat without ZnO coating, and change the average temperature rising rate in the range of 150 to 1000 ° C./s, and the maximum heating temperature Was changed in the range of 900 to 1110 ° C., and the holding time was 0 seconds. In the case where the maximum heating temperature is in the range of 900 to 1010 ° C., it is found that a plated layer mainly formed of Fe ₂ Al ₅ phase is formed, and the flange end surface is excellent in corrosion resistance. However, in the case where the maximum heating temperature is 1110 ° C., it is found that a plated layer mainly composed of ε phase is formed, and the flange end surface corrosion resistance is inferior. From this result, even if the holding time is zero seconds, the plating layer excellent in corrosion resistance mainly by Fe ₂ Al ₅ phase can be obtained by preheating, but even when preheating is performed, the maximum heating temperature is , It can be seen that it is necessary to avoid 1102 ° C. or more at which the ε phase is generated.

No. No. 32 to 36 are No. 1 except that the plating type is GL. The conditions are the same as in 27-31. That is, similar to Al-9Si plating, even in the case of GL plating, by preheating even when the holding time is zero seconds, a plated layer having a main component of Fe ₂ Al ₅ phase and excellent corrosion resistance can be obtained, however, It can be seen that, even when preheating, the maximum heating temperature needs to avoid 1102 ° C. or more at which the ε phase is generated.

No. No.37 to No.39 form Al-9% Si plating with a deposition amount of 20 to 100 g / m ² , no ZnO coating and no preheating, and raise the temperature at an average temperature rising rate of 150 ° C./sec. It is held for 3 seconds. Under any of the conditions, a plated layer excellent in flange end face corrosion resistance was obtained mainly by the Fe ₂ Al ₅ phase. Within the range of ^{20 to} 100 g / m ² of the plating adhesion amount, it can be seen that a plating layer having excellent corrosion resistance can be obtained by the same manufacturing method.

No. Nos. 40 to 42 are No. The conditions are the same except that 37 to 39 and the plating type are different. That is, even when the plating type is GL, it is possible to obtain a plated layer which is excellent in flange end surface corrosion resistance mainly by Fe ₂ Al ₅ phase within the range of the adhesion amount of 20 to 100 g / m ² .

No. 43-46, the Al-9% Si plating formed by coating weight 70 g / ^{m 2,} ZnO was applied a coating of 0.03~3g / ^{m 2} contained in Zn terms, the average heating rate 60 ° C. The temperature is raised to a maximum heating temperature of 1000 ° C./second and held for 1 second. The phase structure of the plating layer is No. 1 having no ZnO coating and similar plating and heating conditions. It was similar to 12. However, the flange end face corrosion resistance, although the amount of ZnO deposited is not the case so different without coating if 0.03 g / ^{m 2} of Zn in terms of the amount of ZnO deposited is 0.1 to 1.0 g / ^{m 2} of Zn terms In the case, it is understood that the corrosion resistance is improved as compared with the case without the application. However, even if the ZnO deposition amount is further increased to 3.0 g / m ^{2 in} terms of Zn, it can be seen that the further improvement from the case where the ZnO deposition amount is 1.0 g / m ² is small. From these results, it is understood that the appropriate adhesion amount of ZnO is 0.1 to 1.0 g / m ² in terms of Zn.

No. For 47 to 49, the Si concentration in Al-Si plating is changed in the range of 6 to 15% by mass, and the plating adhesion amount is 70 g / m ^2, and there is no ZnO application or preheating, and the average temperature elevation rate of 150 ° C. / The temperature is raised in seconds, and held at a maximum heating temperature of 1000 ° C. for 1 second. When the Si concentration is in the range of 6 to 15% by mass, a plated layer excellent in flange end face corrosion resistance with the Fe ₂ Al ₅ phase main component is obtained under the above heating conditions.

  No. 50 is a comparative example which applied the non-plating steel to the STAF process. Fe oxide scale formed and the appearance deteriorated. Moreover, it is known that Fe scale degrades chemical conversion treatment property in the manufacture of parts for motor vehicles. From these results, it is understood that it is appropriate to use plated steel in this process.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Al plated steel pipe parts 3 hollow part 5 flange part 11 steel materials 13 plated layer 100 Al plated steel pipe 101 steel pipe 103 Al plated layer 200 metal mold 201 upper mold 203 lower mold

Claims (15)

An Al-plated steel pipe having an Al-plated layer containing Al and Si is disposed between at least one set of molds having a predetermined shape, and is then energized to a heating temperature within the range of Ac3 transformation point to less than 1102 ° C. A heating step of heating by heating and holding the heating temperature for 1 second or more and 5 minutes or less;
The air-plated steel pipe is hot-blow molded by supplying air of a predetermined pressure to the hollow portion of the aluminum-plated steel pipe that has reached the heating temperature, and tension is applied to form an overhang from the surface of the Al-plated steel pipe Outgoing process,
After the mold is clamped at a predetermined pressure, air of a predetermined pressure is supplied to the hollow portion of the Al-plated steel pipe, and a hollow portion having a predetermined cross-sectional shape and a protrusion from the outer surface of the hollow portion Forming a flange portion, and
A method of producing an Al-plated steel pipe component, including: Preheating the Al-plated steel pipe having an Al plating layer containing Al and Si to a predetermined temperature less than 1102 ° C .;
Placing the preheated Al-plated steel pipe between at least one set of molds having a predetermined shape, and heating by heating to a heating temperature within the range of Ac3 transformation point to less than 1102 ° C .; ,
The air-plated steel pipe is hot-blow molded by supplying air of a predetermined pressure to the hollow portion of the aluminum-plated steel pipe that has reached the heating temperature, and tension is applied to form an overhang from the surface of the Al-plated steel pipe Outgoing process,
After the mold is clamped at a predetermined pressure, air of a predetermined pressure is supplied to the hollow portion of the Al-plated steel pipe, and a hollow portion having a predetermined cross-sectional shape and a protrusion from the outer surface of the hollow portion Forming a flange portion, and
A method of producing an Al-plated steel pipe component, including: Deposition amount of the Al plating layer is in the range of one face per ^{10g / m 2 ~100g / m 2} , the production method of Al-plated steel component according to claim 1 or 2.   The Al plating layer according to any one of claims 1 to 3, wherein the Al plating layer is an Al-6 to 15 mass% Si plating layer or a 55 mass% Al-Zn-1.6 mass% Si plating layer. Method of manufacturing Al-plated steel pipe parts. The Al plating layer after the forming step is a plating layer mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al alloy and the ε phase of the Fe—Al alloy and Al absent. The manufacturing method of Al plated steel pipe parts in any one of 4. In the heating step,
Electric heating equipment for electrically heating a portion of the Al plated steel pipe at a position to be the overhanging portion at least in the overhanging step, and electric heating for electrically heating a portion of the Al plated steel pipe at a position not for the overhanging portion Equipment and, separately,
The aluminum plating according to any one of claims 1 to 4, wherein the portion of the Al plated steel pipe corresponding to the position to be the overhanging portion is heated to a heating temperature within the range of Ac3 transformation point to less than 1102 ° C. Method of manufacturing steel pipe parts. The Al plating layer covering the flange portion after the forming step is mainly composed of the Fe ₂ Al ₅ phase of the Fe—Al alloy and the plating layer in which the ε phase of the Fe—Al alloy and Al do not exist The manufacturing method of Al plating steel pipe parts of Claim 6 which becomes. The chemical composition of the base steel of the Al-plated steel pipe is, by mass%,
C: 0.1 to 0.3%
Si: 0.01 to 0.50%
Mn: 0.5 to 3.0%
P: 0.003 to 0.050%
S: 0.05% or less Cr: 0.1 to 0.5%
Ti: 0.01 to 0.10%
Al: 1% or less B: 0.0002 to 0.0004%
The manufacturing method of Al plated steel pipe parts according to any one of claims 1 to 7, wherein N: 0.01% or less is contained, and the balance is made of Fe and impurities.   The base steel of the Al-plated steel pipe is replaced with a part of the remaining Fe, 1% by mass or less Cu, 2% by mass or less Ni, 1% by mass or less Mo, 1% by mass or less V, and 1 The method for producing an Al-plated steel pipe component according to claim 8, further comprising at least one of Nb at a mass% or less. A hollow portion having a predetermined cross-sectional shape;
A flange portion projecting from the outer surface of the hollow portion;
At least
The hollow portion and the flange portion are made of the same steel material as a material, and are integrally formed without the joint surface between the hollow portion and the flange portion.
The surfaces of the hollow portion and the flange portion are coated with a plating layer mainly composed of an Fe-Al based alloy,
The plating layer mainly composed of the Fe-Al based alloy covering the end of the flange portion is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al based alloy, and the ε phase of the Fe-Al based alloy and Al Al-plated steel pipe parts, which is a plating layer that does not exist. The plating layer mainly composed of the Fe-Al based alloy covering the surface of the hollow part is mainly composed of the Fe ₂ Al ₅ phase of the Fe-Al based alloy, and the ε phase and Al of the Fe-Al based alloy The Al plated steel pipe component according to claim 10, which is a plating layer which does not exist. When the plated layer is measured by an X-ray diffractometer using a Co tube, a peak is observed within the range of the diffraction angle 2θ: 54 ° to 55.3 °,
Diffraction angle 2 [Theta]: an average intensity in the range of 40.6 ° to 41 ° and _{I A,} the diffraction angle 2 [Theta]: mean intensity in the range of 58 ° through 59 ° to the _{I B,} diffraction angle 2θ: 54 ° ~55.3 The aluminum-plated steel pipe component according to claim 10 or 11, wherein the relationship represented by the following formula (1) holds, when the maximum intensity of the peak in the range of ° is I _C.

The plated layer is measured by an X-ray diffractometer using a Co tube, and the average intensity of the diffraction angle 2θ: 34 ° to 35 ° is _ID , and the diffraction angle 2θ: 37 ° to 38 ° The relationship represented by the following equation (3) holds, where I _E is the average intensity and I _F is the maximum intensity of peaks within the range of diffraction angles 2θ: 35 ° to 37 °. Al plated steel pipe part according to any one of the above.

The plating layer was measured by X-ray diffraction apparatus using a Co tube, the diffraction angle 2 [Theta]: an average intensity in the range of 43.5 ° ~44.5 ° and _{I G,} the diffraction angles 2θ: 46 ° ~47 Assuming that the average intensity in the range of ° is I _H and the maximum intensity of the peak in the range of diffraction angles 2θ: 44.5 ° to 45.4 ° is I _J , it is represented by the following formula (5) The Al plated steel pipe part according to any one of claims 10 to 13, wherein a relation is established.

The Al plated steel pipe part according to any one of claims 10 to 14, which has a continuous deformed closed cross-sectional structure.

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