WO2020138468A1 - Procédé de production d'un élément en acier - Google Patents

Procédé de production d'un élément en acier Download PDF

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Publication number
WO2020138468A1
WO2020138468A1 PCT/JP2019/051543 JP2019051543W WO2020138468A1 WO 2020138468 A1 WO2020138468 A1 WO 2020138468A1 JP 2019051543 W JP2019051543 W JP 2019051543W WO 2020138468 A1 WO2020138468 A1 WO 2020138468A1
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WO
WIPO (PCT)
Prior art keywords
projection
energization
nut
steel
bolt
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Application number
PCT/JP2019/051543
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English (en)
Japanese (ja)
Inventor
元 村山
古迫　誠司
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日本製鉄株式会社
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Publication date
Application filed by 日本製鉄株式会社 filed Critical 日本製鉄株式会社
Priority to JP2020562530A priority Critical patent/JP7131634B2/ja
Publication of WO2020138468A1 publication Critical patent/WO2020138468A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/14—Projection welding

Definitions

  • the present invention relates to a method for manufacturing a steel member, specifically, a method for manufacturing a steel member having one or both of a nut and a bolt.
  • Patent Document 1 discloses a structural member for an automobile, in which a high-strength steel plate and a nut or a bolt are joined by projection welding, as a structural member for an automobile, which has excellent delayed fracture characteristics and static strength characteristics of a welded part, and is a nut A configuration in which a concave portion is locally provided around the projection of the bolt is disclosed.
  • Patent Document 2 discloses an automobile structural member having a nut or a bolt, which is capable of obtaining excellent delayed fracture characteristics and high static strength, for an automobile in which a high-strength steel plate and a nut or a bolt are joined by projection welding.
  • a structural member is disclosed in which the depth of the heat-affected zone in the high-strength steel plate in the plate thickness direction is within a predetermined range.
  • Patent Document 3 the chemical composition of the nut or bolt, and the tensile strength, plate thickness, and carbon equivalent of the high-strength steel plate are defined to appropriately control the hardness and toughness of the joint, and further Projection with excellent static strength such as torque peel strength and push peel strength by defining the ratio of the area of the joint with the high-strength steel plate to the area of the nominal diameter of the nut or bolt within an appropriate range.
  • a method of making a welded joint is disclosed.
  • hot stamping materials made by hot pressing zinc-based plated steel sheets may be used for automobile structural members.
  • the joint strength is higher than when welding is performed on a hot stamp material without a zinc-based plating on the surface. Is more likely to occur.
  • the zinc-based plating means plating containing zinc (hereinafter the same).
  • An object of the present invention is to provide a method for manufacturing a steel member having one or both of a bolt and a bolt.
  • the present inventors diligently studied a method for stably obtaining a high joint strength when joining a nut or a bolt to a zinc-based plated steel material by projection welding. As a result, it was confirmed that the cause of the variation in the bonding strength was the oxide film, which is a high-resistivity element existing on the surface of the steel material.
  • the method comprises a pre-energization step, a cool step, and a main energization step in order, and in the pre-energization step, the height of all the plurality of projections is 0.7 to 0 as compared with that before the pre-energization step.
  • the nut is characterized in that energization is carried out so as to be 1.9 times, the cool step has a time of no energization of 70 ms or more, and a current higher than that in the preliminary energization step flows in the main energization step. And a method for manufacturing a steel member having one or both of bolts.
  • a high joining strength (specifically, indentation peel strength) can be obtained.
  • FIG. 6 is a diagram showing a state in which the coating film is destroyed and removed or thinned, the resistance in the region where the current from the projection flows is made uniform, and the current evenly flows to each projection in the subsequent main energization.
  • FIG. 6B is a diagram showing a case where the thickness of the oxide film on the surface of the steel sheet varies and there is a difference in the current flowing through each projection in the conventional case.
  • the contents of the study conducted by the present inventors to arrive at the present invention will be described.
  • a case of joining a nut to a zinc-based plated hot stamp material by projection welding will be described, but the same applies to the case of joining a bolt.
  • the steel material refers to a steel product including a steel plate and a molded product obtained by molding the steel plate.
  • the inventors of the present invention thought that the reason why the joining strength varies when joining the nut to the zinc-based plated hot stamp material by projection welding is that there is an oxide film, which is a high-resistor, on the surface of the steel sheet. More specifically, it is as follows.
  • an oxide film forms on the surface of the steel sheet.
  • the oxide film is not formed to have a constant thickness, but is formed with a certain shade, that is, a variation in thickness.
  • the oxide film is a high-resistor, so the projection that is in contact with a relatively thin oxide film It becomes easier for the current to flow, and there is a difference in the magnitude of the current flowing through each projection.
  • FIG. 1 shows this schematically.
  • the upper electrode 11a is brought into contact with the nut 14, the lower electrode 11b is brought into contact with the steel plate 12, and further, the plurality of projections 15 included in the nut 14 are brought into contact with the steel plate 12 to produce the upper electrode.
  • Welding is performed by passing a current 16 from 11a toward the lower electrode 11b.
  • FIG. 1A is a diagram showing that the thickness of the oxide film 13 in a region where a current flows from the projection 15 to the steel plate 12 is made uniform by pre-energization, and a current flows uniformly in each projection 15 by the main energization.
  • FIG. 1B is a diagram in which the oxide film 13 has unevenness, that is, variation in thickness, and there is a difference in the current flowing through each projection 15.
  • the press-contact diameter refers to the diameter of the joint surface of the projection 15 that is melted and crushed by the electric current during projection welding and joined to the steel plate 12 to the steel plate 12.
  • the present inventors have confirmed that the zinc-based plated hot stamped material obtained by hot pressing a zinc-based plated steel sheet has a nut attached by projection welding as it is, and a surface oxide film formed by shot blasting.
  • the nut was attached by projection welding after removing, the joining strength was compared by an indentation peeling test.
  • the method of removing the oxide film by shot blasting requires one additional step and cannot solve the problem of high cost. Therefore, the inventors of the present invention changed the welding conditions to carry out the main energization in projection welding.
  • the present invention has been made by studying a method of removing or thinning the oxide film before the step to make the thickness of the oxide film in the region where the current flows from each projection uniform. The present invention will be described below.
  • the method for manufacturing a steel member according to the present invention is a method in which a steel material having a zinc-based plating on the surface and a nut or bolt having a plurality of projections are joined by projection welding in which electric heating is performed while applying pressure, and one of the nut and the bolt is used. Or it is a method of manufacturing a steel member having both.
  • a steel material having a zinc-based plating on the surface and a nut or bolt having a plurality of projections are joined by projection welding in which electric heating is performed while applying pressure, and one of the nut and the bolt is used.
  • it is a method of manufacturing a steel member having both.
  • main energization step as a preliminary energization step
  • pressure is applied with the steel material and multiple projections on the nuts or bolts in contact with each other.
  • a step of passing a current lower than the main energization and a step of not energizing as a cool step are provided.
  • the oxide film 13 of the steel plate 12 that is in contact with each projection 15 is destroyed and removed or thinned. Since the oxide film 13 has a high specific resistance value and its distribution is not always uniform, the oxide film 13 is destroyed and removed or thinned in the pre-energization process to oxidize the region where the current 16 flows from each projection 15.
  • the thickness of the coating film 13 is made uniform, and the resistance in the current path at the contact point of each projection 15 is made substantially uniform. Therefore, in the main energization process for forming the joint, as shown in FIG. 1A, the density of the current 16 in each projection 15 becomes uniform, and the joint can be formed uniformly at each point.
  • the projection height (see FIG. 2) of all the projections of the nut should be 0.7 to 0.9 times that before the start of pre-energization. ..
  • adjust the magnitude of current, energizing time, pressure, etc. in the pre-energizing step Then do it.
  • a method for carrying out the pre-energization process so that the projection heights of all the plurality of projections are 0.7 to 0.9 times as high as before the start of pre-energization will be described.
  • Examples of the method include a method in which test welding is performed only with preliminary energization using a flat steel plate, and various conditions for the preliminary energization step are determined in advance.
  • the projection height before and after the pre-energization step in the test welding is the test welding only with pre-energization using a steel plate that is a flat plate, and before and after pre-energization, for example, with a caliper or laser type measuring instrument. Just measure.
  • the preliminary energizing current, the energizing time, and the pressurizing force at which the height of all projections is 0.7 to 0.9 times the height before the starting of the pre-energizing are determined.
  • the subsequent projection welding may be performed using the applied pressure.
  • the projection height before and after the pre-energization step is, for example, in a state where the nut or the bolt is in contact with the steel plate, at the position of each projection, the total thickness of the steel plate and the nut or the bolt including the projection is measured, It is obtained as a value obtained by subtracting the thickness of the steel plate and the thickness of the portion excluding the projection of the nut or bolt from the total thickness.
  • the projection height of the projection after pre-energization is in the range of more than 0.9 to 1.0 times before the start of pre-energization, the effect of destroying the oxide film and removing or thinning the oxide film is hardly obtained by pre-energization. Therefore, the current density at each projection position (often 3 or 4) is not uniform. If the projection height of the projection after pre-energization is less than 0.7 times that before start of pre-energization, the projection will be excessively crushed and the current density required in the main energization step will not be obtained, and proper welding will be performed. Disappear.
  • the current value of the pre-energization process is lower than the current value of the main energization process, and can be, for example, 1/3 to 1/5 of the current value of the main energization process.
  • the current value per projection in the preliminary energization step can be set to 1.0 to 1.4 kA.
  • the time required for the pre-energization process is about several tens of ms, and since it is performed by an apparatus that performs projection welding, the cost is not significantly affected.
  • a process (cool process) having a de-energization time that is the time for which electricity is not applied for 70 ms or more (that is, electricity is not applied) is provided.
  • the cool process if the current is set to 0, the pressurized state may be maintained.
  • the temperatures of the projections are made uniform, and the ease of the current flowing through the projections is also made uniform.
  • the current flowing through each projection is made uniform by the main energization, the variation in the joint strength between the steel plate and the nut can be reduced, and the indentation peel strength Cp (one-side process capability index) is increased. It is more effective to set the non-energization time to 80 ms or more, 180 ms or more, or 200 ms or more.
  • the oxide film of the steel sheet in contact with each projection is destroyed and removed or thinned, and the temperature of each projection is made uniform in the cool step, so that each projection in each subsequent energization step. It is possible to evenly flow an electric current to the steel plate, and it is possible to obtain a steel member having a high joint strength between the steel plate and the nut and having a small variation in the joint strength.
  • the projection height before projection welding is 0.9 to 1.0 mm mm
  • the projection height after main energization is preferably near 0 mm.
  • the process before the pre-energization process and the process after the main energization process are not particularly limited. As in the case of general projection welding, there may be a step of applying only pressure and holding without applying current.
  • the steel material used in the method for producing a steel member of the present invention is not particularly limited as long as it is a steel material having a zinc-based plating on the surface.
  • Hot pressing is mentioned as a material that easily forms an oxide film on the steel surface, and since hot pressing is often applied to high strength steel sheets, especially for high strength zinc-based plated steel sheets used for hot stamping materials. Is suitable.
  • Examples of the steel material having a high-strength zinc-based plating include a zinc-based plated steel material having a tensile strength of 1100 MPa or more before joining.
  • the variation in the bonding strength due to projection welding is often caused by the oxide film of the high resistance material on the surface of the steel material, so it is suitable for steel materials with a contact resistance of 1 m ⁇ or more at room temperature.
  • a contact resistance of 1 m ⁇ or more at room temperature.
  • Fig. 3 shows the method of measuring contact resistance.
  • a single steel plate 32 having a zinc-based plating 33 on its surface is sandwiched by an upper electrode 31a and a lower electrode 31b for spot welding.
  • a current I of 1 A is applied to the electrodes.
  • the voltage V1 between the upper electrode 31a and the steel plate 32 and the voltage V2 between the lower electrode 31b and the steel plate 32 are measured.
  • the electrical resistance between the upper electrode 31a and the steel plate 32 is R1
  • the electrical resistance between the lower electrode 31b and the steel plate 32 is R3
  • the resistance due to the specific resistance of the bulk (base material) of the steel plate 32 is R2.
  • R2 can be approximated to zero.
  • the resistances of the upper and lower electrodes 31a and 31b can be approximated to zero. Therefore, the relationship between the measured voltages V1 and V2 and the electrical resistances R1 and R3 can be approximated as follows.
  • the larger resistance value of R1 and R3 is the contact resistance in the present invention.
  • FIG. 3 shows the steel plate 32 having the zinc-based plating 33 formed on both surfaces, a steel plate having the zinc-based plating formed on only one surface may be used in the present invention.
  • a nut with a substantially hemispherical projection on the joint surface was used in accordance with JIS B 1196:2010. More specifically, the projection distance (projection height) of three or four (comparative example No. 10 has four projections) projections of 0.90 mm or 1.00 mm in the strength category 8T. A nut was used.
  • a pierce hole was formed in a steel plate with a drill, and then the center of the pierce hole and the center of the screw hole of the nut were roughly matched by using a guide pin. In this state, the steel plate and the nut were overlapped with each other, and current was applied to the upper and lower electrodes while applying electric current to perform projection welding.
  • a stationary type projection welding machine was used for the projection welding, and after the initial pressurization of 0.5 s, the 0.17 s electrode was held after the preliminary energization process, the cool process and the main energization process under the conditions shown in Table 1. Later, the pressure was released. The pressure applied by the upper and lower electrodes was set to the conditions shown in Table 1 throughout the entire process. For each of the conditions shown in Table 1, projection welding was performed under the same welding conditions to produce 15 test materials.
  • an average indentation peel strength of 10.5 kN or more and a Cp of 1.33 or more were defined as “OK”, and those that did not meet this criterion were defined as “NG”.
  • the indentation peel strength of the nut can be stably obtained at a high value without variation.
  • the average value of the indentation peel strength was the same as that of the manufacturing method of the present invention, but The variation was large, and the judgment of the one-sided process capability index was “NG”.
  • Figure 4 shows the fracture surface of the joint after indentation peeling test.
  • (A) is the invention example (No. 1)
  • (b) is the comparative example (No. 8) in which the pre-energization and the cooling process were not performed.
  • each (three) projection joints were fractured substantially evenly, but in (b) there was a difference in fracture state, and it was confirmed that zinc oxide remained in the joints. It was
  • FIG. 5 shows the relationship between the non-energization time in the cool process and the one-side process capability index. It was confirmed that the one-side process capability index can be increased by setting the non-energization time in the cool process to 70 ms or more.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Resistance Welding (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

La présente invention concerne un procédé de production d'un élément en acier ayant un écrou et/ou un boulon avec lequel une force d'assemblage élevée peut être obtenue de manière stable. Ce procédé de production d'un élément en acier, dans lequel l'élément en acier est fabriqué par soudage par projection, est pourvu de manière séquentielle d'une étape d'excitation préliminaire, d'une étape de refroidissement ayant un temps de non excitation supérieur ou égal à 70 ms, et d'une étape d'excitation principale au cours de laquelle un courant supérieur à celui de l'étape d'excitation préliminaire est appliqué.
PCT/JP2019/051543 2018-12-27 2019-12-27 Procédé de production d'un élément en acier WO2020138468A1 (fr)

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JP2020562530A JP7131634B2 (ja) 2018-12-27 2019-12-27 鋼部材の製造方法

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JP2018-246055 2018-12-27
JP2018246055 2018-12-27

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112122760A (zh) * 2020-09-15 2020-12-25 湖北长平汽车装备有限公司 一种防弹钢板与螺母焊接工艺

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59699B2 (ja) * 1974-12-27 1984-01-07 トヨタ自動車株式会社 コウドホシヨウソウチ
JP2005297054A (ja) * 2004-04-16 2005-10-27 Nippon Steel Corp プロジェクション溶接方法及びプロジェクション溶接継手並びにプロジェクション溶接構造体
JP2012179646A (ja) * 2011-03-02 2012-09-20 Nippon Steel Corp 溶接部の遅れ破壊特性並びに静的強度特性に優れた自動車用構造部材、および、その製造方法

Family Cites Families (2)

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Publication number Priority date Publication date Assignee Title
JPH11764A (ja) * 1997-04-14 1999-01-06 Sekisui Chem Co Ltd 表面処理鋼材のプロジェクション溶接方法
JP5900699B2 (ja) 2013-10-04 2016-04-06 Ｊｆｅスチール株式会社 抵抗スポット溶接方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59699B2 (ja) * 1974-12-27 1984-01-07 トヨタ自動車株式会社 コウドホシヨウソウチ
JP2005297054A (ja) * 2004-04-16 2005-10-27 Nippon Steel Corp プロジェクション溶接方法及びプロジェクション溶接継手並びにプロジェクション溶接構造体
JP2012179646A (ja) * 2011-03-02 2012-09-20 Nippon Steel Corp 溶接部の遅れ破壊特性並びに静的強度特性に優れた自動車用構造部材、および、その製造方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112122760A (zh) * 2020-09-15 2020-12-25 湖北长平汽车装备有限公司 一种防弹钢板与螺母焊接工艺

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JP7131634B2 (ja) 2022-09-06

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