KR102012132B1 - Resistance spot welding method - Google Patents

Resistance spot welding method Download PDF

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KR102012132B1
KR102012132B1 KR1020180100395A KR20180100395A KR102012132B1 KR 102012132 B1 KR102012132 B1 KR 102012132B1 KR 1020180100395 A KR1020180100395 A KR 1020180100395A KR 20180100395 A KR20180100395 A KR 20180100395A KR 102012132 B1 KR102012132 B1 KR 102012132B1
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welding
heat input
resistance
current
input amount
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KR1020180100395A
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Korean (ko)
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유지영
장순근
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현대제철 주식회사
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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
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts
    • 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
    • B23K11/24—Electric supply or control circuits therefor
    • 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
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • B23K11/252—Monitoring devices using digital means
    • B23K11/257—Monitoring devices using digital means the measured parameter being an electrical current
    • 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
    • B23K11/24—Electric supply or control circuits therefor
    • B23K11/25—Monitoring devices
    • B23K11/252—Monitoring devices using digital means
    • B23K11/258—Monitoring devices using digital means the measured parameter being a voltage
    • 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
    • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
    • B23K31/12—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to investigating the properties, e.g. the weldability, of materials
    • B23K31/125—Weld quality monitoring

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  • Mechanical Engineering (AREA)
  • Quality & Reliability (AREA)
  • Resistance Welding (AREA)

Abstract

The present invention relates to a resistance spot welding method which can soundly maintain the quality of a weld even if welding environments are changed. The resistance spot welding method comprises: a reference welding condition detection step of detecting a reference welding current and a reference welding time for allowing tensile strength of a weld to become higher than or equal to reference strength; a reference dynamic resistance detection step of detecting a reference dynamic resistance beta peak while performing pre-welding by the reference welding current; a reference heat input setting step of setting a heat input acting on a weld of pre-welding during the reference welding time as a reference heat input; a main welding start step of starting main welding by the reference welding current; and a welding time control step of detecting a dynamic resistance beta peak while performing main welding, calculating a target heat input from the reference dynamic resistance beta peak, the reference heat input, and the dynamic resistance beta peak, and continuing welding until a heat input acting on a weld of main welding reaches the target heat input.

Description

저항 스폿 용접방법{RESISTANCE SPOT WELDING METHOD}Resistance spot welding method {RESISTANCE SPOT WELDING METHOD}

본 발명은 저항 스폿 용접방법에 관한 것으로서, 보다 상세하게는 건전한 저항 스폿 용접부를 생성하기 위한 저항 스폿 용접방법에 관한 것이다.The present invention relates to a resistance spot welding method, and more particularly, to a resistance spot welding method for producing a sound resistance spot weld.

일반적으로 저항 스폿 용접은 용접대상이 되는 소재를 용접용 전극으로 가압한 상태에서 전류를 흘리고, 이때 발생하는 저항 발열로 소재를 용융시켜 접합하는 용접 방법을 의미한다. 용접 전류가 소재를 통과할 때 발생하는 저항 발열에 의해 모재의 온도가 상승하여 저항이 증가하는 현상과, 모재가 용융하여 형성되는 너깃의 성장에 의해 통전 단면적이 증가하여 저항이 감소하는 현상 사이의 상관관계에 의해 저항이 동적으로 변화하는데 이를 동저항이라고 한다.In general, resistance spot welding refers to a welding method in which a current flows in a state in which a material to be welded is pressed by a welding electrode, and the material is melted and joined by resistance heat generated at this time. Between the phenomenon in which the temperature of the base material rises due to the resistance heat generated when the welding current passes through the material, the resistance increases, and the current passing cross-sectional area increases due to the growth of the nugget formed by melting the base material, thereby decreasing the resistance. The resistance changes dynamically by correlation, which is called dynamic resistance.

본 발명의 배경기술은 대한민국 등록특허 제1871077호(2018.06.19 등록, 발명의 명칭: 저항 스폿 용접 방법 및 용접 구조물)에 개시되어 있다.Background art of the present invention is disclosed in Republic of Korea Patent No. 1871077 (Registered June 19, 2018, the name of the invention: resistance spot welding method and welding structure).

본 발명은 용접 환경이 가변되더라도 용접부의 품질을 건전하게 유지할 수 있는 저항 스폿 용접방법을 제공하는데 그 목적이 있다.SUMMARY OF THE INVENTION An object of the present invention is to provide a resistance spot welding method capable of maintaining the quality of a weld even when the welding environment is variable.

본 발명에 따른 저항 스폿 용접방법은 용접부의 인장강도가 기준강도 이상이 되는 기준용접전류와 기준용접시간을 검출하는 기준용접조건 검출단계; 상기 기준용접전류로 기(旣)용접을 수행하면서, 기준동저항 베타피크를 검출하는 기준동저항 검출단계; 상기 기준용접시간동안 기용접의 용접부에 작용한 입열량을 기준입열량으로서 설정하는 기준입열량 설정단계; 상기 기준용접전류로 본(本)용접을 개시하는 본용접 개시단계; 및 본용접을 수행하면서 동저항 베타피크를 검출하고, 상기 기준동저항 베타피크, 상기 기준입열량, 상기 동저항 베타피크로부터 목표입열량을 산출하며, 본용접의 용접부에 작용하는 입열량이 상기 목표입열량에 도달되기까지 용접을 지속하는 용접시간 제어단계;를 포함하는 것을 특징으로 한다.The resistance spot welding method according to the present invention includes a reference welding condition detecting step of detecting a reference welding current and a reference welding time in which the tensile strength of the weld portion is equal to or higher than the reference strength; A reference dynamic resistance detecting step of detecting a reference dynamic resistance beta peak while performing preliminary welding with the reference welding current; A reference heat input setting step of setting a heat input amount acting on the welding part of the pre-weld as the reference heat input amount during the reference welding time; A main welding start step of starting main welding with the reference welding current; And detecting the copper resistance beta peak while performing main welding, calculating a target heat input from the reference copper resistance beta peak, the reference heat input amount and the copper resistance beta peak, and the heat input amount acting on the welding part of the main welding. And a welding time control step of continuing the welding until the target heat input amount is reached.

상기 기준용접조건 검출단계는, 용접전류와 용접시간을 가변시키며 기용접을 수행하는 시험용접단계; 상기 용접부의 인장강도가 기준강도 이상이면서, 소재의 날림이 발생되지 않는 용접전류와 용접시간 범위를 적정용접구간으로서 찾아내는 적정범위 검출단계; 및 상기 적정용접구간 내에서 상기 기준용접전류와 상기 기준용접시간을 선정하는 기준조건 선정단계;를 포함하는 것을 특징으로 한다.The reference welding condition detecting step may include: a test welding step of performing welding by varying a welding current and a welding time; An appropriate range detecting step of finding a welding current and a welding time range in which the tensile strength of the weld portion is equal to or greater than the reference strength and the material does not fly, as a proper welding section; And a reference condition selecting step of selecting the reference welding current and the reference welding time within the proper welding section.

상기 기준동저항 검출단계는, 상기 기준용접조건으로 정전류 제어 용접을 수행하면서 전류와 전압을 계측하는 기준용접계측단계; 계측된 전류와 전압으로부터 동저항을 산출하는 동저항산출단계; 및 설정 용접시간 경과 후, 가장 큰 저항값을 상기 기준동저항 베타피크로서 설정하는 기준동저항설정단계;를 포함하는 것을 특징으로 한다.The reference dynamic resistance detecting step includes: a reference welding measurement step of measuring current and voltage while performing constant current control welding under the reference welding condition; A copper resistance calculation step of calculating a copper resistance from the measured current and voltage; And a reference dynamic resistance setting step of setting the largest resistance value as the reference dynamic resistance beta peak after the set welding time has elapsed.

상기 기준입열량(Qref)은, 기용접을 수행하면서 측정한 전류(I)와 전압(V), 상기 기준용접시간(tref)을, 하기 식

Figure 112018084735505-pat00001
에 대입하여 산출되는 것을 특징으로 한다.The reference heat input (Q ref ), the current (I) and voltage (V) measured while performing pre -welding, the reference welding time (t ref ), the following equation
Figure 112018084735505-pat00001
It is characterized in that it is calculated by substitution.

상기 목표입열량(Qtarget)은, 상기 기준입열량(Qref), 상기 기준동저항 베타피크(Bref), 상기 동저항 베타피크(Bweld)를, 하기 식

Figure 112018084735505-pat00002
에 대입하여 산출되는 것을 특징으로 한다.The target heat input (Q target ), the reference heat input (Q ref ), the reference dynamic resistance beta peak (B ref ), the dynamic resistance beta peak (B weld ), the following formula
Figure 112018084735505-pat00002
It is characterized in that it is calculated by substitution.

상기 용접시간 제어단계는, 본용접을 진행하면서 상기 동저항 베타피크를 검출하는 동저항 검출단계; 상기 동저항 베타피크와 상기 기준동저항 베타피크 간의 비율과, 상기 기준입열량으로부터 목표입열량을 산출하는 목표입열량 산출단계; 본용접의 용접부에 작용하는 입열량과 목표입열량을 실시간으로 비교하는 입열량 비교단계; 본용접의 용접부에 작용하는 입열량이 상기 목표입열량에 도달되기까지 본용접을 지속하는 목표입열량 확보단계; 및 상기 용접부에 작용하는 입열량이 상기 목표입열량에 도달되면 본용접을 종료하는 본용접 종료단계;를 포함하는 것을 특징으로 한다.The welding time control step may include a dynamic resistance detection step of detecting the dynamic resistance beta peak while performing main welding; A target heat input calculating step of calculating a target heat input amount from the ratio between the copper resistance beta peak and the reference copper resistance beta peak and the reference heat input amount; A heat input comparing step of comparing a heat input amount acting on the welded portion of the main welding with a target input heat value in real time; Securing a target heat input amount for continuing the main welding until the heat input amount acting on the welded portion of the main welding reaches the target heat input value; And a main welding end step of terminating the main welding when the heat input amount acting on the welding portion reaches the target heat input amount.

본 발명에 따른 저항 스폿 용접방법은, 기준용접전류에 해당되는 정전류를 전극에 인가하며 본용접을 수행함에 있어서, 용접 환경에 맞추어 목표입열량 및 용접시간을 가변시켜 적용함으로써, 입열량 과다 또는 입열량 미달로 인한 용접 품질 저하 및 용접 불량을 방지할 수 있다.In the resistance spot welding method according to the present invention, in performing the main welding while applying a constant current corresponding to the reference welding current to the electrode, by applying the target heat input and welding time in accordance with the welding environment, excessive heat input or It is possible to prevent weld quality deterioration and weld failure due to insufficient calories.

본 발명은, 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 높은 경우, 베타피크비의 비율로, 기준입열량(Qref)보다 목표입열량(Qtarget)을 작게 설정함으로써, 본용접 시 입열량 과다로 인한 용접부 날림 현상 및 불량을 방지하고, 설정 강도 이상의 인장강도를 가지는 건전한 용접부를 생성할 수 있다.In the present invention, when the dynamic resistance beta peak (B weld ) is higher than the reference dynamic resistance beta peak (B ref ), the target heat input (Q target ) is smaller than the reference heat input (Q ref ) as a ratio of the beta peak ratio. By setting, it is possible to prevent the welding part blowing phenomenon and the defect due to excessive heat input during the main welding, and to generate a healthy weld part having a tensile strength of more than the set strength.

또한, 본 발명은, 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 낮은 경우, 베타피크비의 비율로, 기준입열량(Qref)보다 목표입열량(Qtarget)을 크게 설정함으로써, 본용접 시 입열량 미달로 인한 너겟 축소 및 인장강도 저하를 방지하고, 설정 강도 이상의 인장강도를 가지는 건전한 용접부를 생성할 수 있다.In addition, the present invention, when the dynamic resistance beta peak (B weld ) is lower than the reference dynamic resistance beta peak (B ref ), the ratio of the beta peak ratio, the target heat input (Q target ) than the reference heat input (Q ref ) By setting a larger value, it is possible to prevent nugget reduction and decrease in tensile strength due to insufficient heat input during main welding, and to generate a healthy weld having a tensile strength of more than the set strength.

도 1은 본 발명의 일실시예에 따른 저항 스폿 용접방법을 설명하고자 도시한 플로우차트이다.
도 2는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 기준용접조건 검출단계에 의해 기준용접전류와 기준용접시간을 검출하는 일례를 설명하고자 나타낸 표이다.
도 3은 본 발명의 일실시예에 따른 저항 스폿 용접방법에서 전류와 전압을 계측하는 과정을 설명하고자 도시한 용접기의 개념도이다.
도 4는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 기준동저항 검출단계에 의해 기준동저항 베타피크를 검출하는 일례를 설명하고자 도시한 그래프이다.
도 5는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 용접시간 제어단계에서 검출된 동저항을 기준동저항과 비교하여 설명하고자 도시한 그래프이다.
도 6은 도 5에 도시된 그래프 상의 동저항 베타피크를 기준동저항 베타피크와 수치로 비교하여 나타낸 표이다.
도 7은 본 발명의 일실시예에 따른 저항 스폿 용접방법의 용접시간 제어단계에 의해 조절된 용접시간을 기준용접시간과 비교하여 도시한 그래프이다.1 is a flowchart illustrating a resistance spot welding method according to an embodiment of the present invention.
2 is a table for explaining an example of detecting the reference welding current and the reference welding time by the reference welding condition detection step of the resistance spot welding method according to an embodiment of the present invention.
3 is a conceptual diagram illustrating a welding machine to explain a process of measuring current and voltage in a resistance spot welding method according to an exemplary embodiment of the present invention.
4 is a graph illustrating an example of detecting the reference dynamic resistance beta peak by the reference dynamic resistance detection step of the resistance spot welding method according to an embodiment of the present invention.
5 is a graph illustrating the comparison of the copper resistance detected in the welding time control step of the resistance spot welding method according to an embodiment of the present invention with reference copper resistance.
FIG. 6 is a table comparing the dynamic resistance beta peak on the graph shown in FIG. 5 with the reference dynamic resistance beta peak.
7 is a graph showing the welding time adjusted by the welding time control step of the resistance spot welding method according to an embodiment of the present invention in comparison with the standard welding time.

이하 첨부된 도면들을 참조하여 본 발명에 따른 저항 스폿 용접방법의 실시예를 설명한다. 이러한 과정에서 도면에 도시된 선들의 두께나 구성요소의 크기 등은 설명의 명료성과 편의상 과장되게 도시되어 있을 수 있다. 또한, 후술되는 용어들은 본 발명에서의 기능을 고려하여 정의된 용어들로써, 이는 사용자, 운용자의 의도 또는 관례에 따라 달라질 수 있다. 그러므로, 이러한 용어들에 대한 정의는 본 명세서 전반에 걸친 내용을 토대로 내려져야 할 것이다.Hereinafter, an embodiment of a resistance spot welding method according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom. Therefore, definitions of these terms should be made based on the contents throughout the specification.

도 1은 본 발명의 일실시예에 따른 저항 스폿 용접방법을 설명하고자 도시한 플로우차트이다.1 is a flowchart illustrating a resistance spot welding method according to an embodiment of the present invention.

도 1을 참조하면, 본 발명의 일실시예에 따른 저항 스폿 용접방법은, 기준용접조건 검출단계(S1), 기준동저항 검출단계(S2), 기준입열량 설정단계(S3), 본용접 개시단계(S4), 용접시간 제어단계(S5)를 포함한다.1, the resistance spot welding method according to an embodiment of the present invention, the reference welding condition detection step (S1), the reference dynamic resistance detection step (S2), the reference heat input amount setting step (S3), the start of the main welding Step S4, welding time control step S5.

기준용접조건 검출단계(S1)에서는 용접부의 인장강도가 기준강도 이상이 되는 기준용접전류와 기준용접시간(tref)을 검출한다. 기준동저항 검출단계(S2)에서는 기준용접전류로 기(旣)용접을 수행하면서, 기준동저항 베타피크(Bref)를 검출한다. 기준입열량 설정단계(S3)에서는 기준용접시간(tref) 동안 기용접의 용접부에 작용한 입열량을 기준입열량(Qref)으로서 설정한다.In the reference welding condition detecting step S1, the reference welding current and the reference welding time t ref at which the tensile strength of the welded portion is equal to or greater than the reference strength are detected. In the reference dynamic resistance detecting step (S2), while performing standard welding with the reference welding current, the reference dynamic resistance beta peak B ref is detected. In the reference heat input amount setting step S3, the heat input amount acting on the welding part of the pre-weld during the reference welding time t ref is set as the reference heat input amount Q ref .

본용접 개시단계(S4)에서는 기준용접전류로 본(本)용접을 개시한다. 용접시간 제어단계(S5)에서는 본용접을 수행하면서 동저항 베타피크(Bweld)를 검출하고, 기준동저항 베타피크(Bref), 기준입열량(Qref), 동저항 베타피크(Bweld)로부터 목표입열량(Qtarget)을 산출하며, 본용접의 용접부에 작용하는 입열량이 목표입열량(Qtarget)에 도달되기까지 용접을 지속한다.In the main welding start step (S4), main welding starts with the reference welding current. The welding time control step (S5), and while carrying out the welding detecting such resistance beta peak (B weld), based on the same resistance beta peak (B ref), the reference heat input (Q ref), copper resistance beta peak (B weld ), And the target heat input Q target is calculated, and the welding is continued until the heat input amount acting on the welded portion of the main welding reaches the target heat input Q target .

도 2는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 기준용접조건 검출단계에 의해 기준용접전류와 기준용접시간을 검출하는 일례를 설명하고자 나타낸 표이다.2 is a table for explaining an example of detecting the reference welding current and the reference welding time by the reference welding condition detection step of the resistance spot welding method according to an embodiment of the present invention.

도 1, 도 2를 참조하면, 본 발명의 일실시예에 따른 기준용접조건 검출단계(S1)는, 시험용접단계(S1-1), 적정범위검출단계(S1-2), 기준조건선정단계(S1-3)를 포함한다.1 and 2, the reference welding condition detection step (S1) according to an embodiment of the present invention, the test welding step (S1-1), the appropriate range detection step (S1-2), the reference condition selection step (S1-3).

시험용접단계(S1-1)에서는 도 2의 표에 나타난 바와 같이 용접전류와 용접시간을 설정 간격으로 가변시키며 시험용접을 수행한다. 적정범위검출단계(S1-2)에서는 용접부의 인장강도가 기준강도 이상이면서, 소재의 날림(expulusion)이 발생되지 않는 용접전류와 용접시간 범위를 적정용접구간(A)으로서 찾아낸다.In the test welding step (S1-1), as shown in the table of FIG. 2, the test current is performed by varying the welding current and the welding time at predetermined intervals. In the proper range detection step (S1-2), the welding current and the welding time range where the tensile strength of the welded portion is equal to or greater than the reference strength and the material does not occur, are found as the appropriate welding interval (A).

용접부의 인장강도를 평가함에 있어서는, 용접부를 가지는 제품의 적용 조건에 따라 기준강도를 설정해 두고, 용접부의 인장강도가 기준강도 이상이면 적정용접구간(A)에 해당되는 것으로 판단할 수 있다. 용접 전류가 과다하면 용접부에서 용융된 금속이 비산되는 날림 현상이 발생되는데, 이는 불량으로 판단되어, 용접부의 인장강도가 기준강도 이상이더라도 기준용접조건(A)에서 제외된다. 도 2의 표에서 B구간은 인장강도가 기준강도 이하인 불량용접구간에 해당되고, C구간은 날림이 발생되는 불량용접구간에 해당된다.In evaluating the tensile strength of the weld, the reference strength is set according to the application conditions of the product having the weld. If the tensile strength of the weld is equal to or greater than the reference strength, it can be determined that it corresponds to the appropriate welding section (A). When the welding current is excessive, a flying phenomenon in which molten metal is scattered in the weld portion is generated, which is determined to be inferior, and is excluded from the reference welding condition (A) even if the tensile strength of the weld portion is higher than the reference strength. In the table of FIG. 2, section B corresponds to a poor welding section in which the tensile strength is less than or equal to the reference strength, and section C corresponds to a poor welding section in which flying occurs.

기준조건선정단계(S1-3)에서는 적정용접구간(A) 내에서 기준용접전류와 기준용접시간을 선정한다. 일례로, 도 2의 표에 나타난 기준용접구간(A) 내에서 A'를 기준용접조건으로 선정할 수 있고, 이때, 기준용접전류는 7.5kA, 기준용접시간(tref)은 410ms가 된다.In the reference condition selection step (S1-3), the reference welding current and the reference welding time are selected within the appropriate welding section (A). For example, A 'may be selected as a reference welding condition in the reference welding section A shown in the table of FIG. 2, where the reference welding current is 7.5 kA and the reference welding time t ref is 410 ms.

도 3은 본 발명의 일실시예에 따른 저항 스폿 용접방법에서 전류와 전압을 계측하는 과정을 설명하고자 도시한 용접기의 개념도이고, 도 4는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 기준동저항 검출단계에 의해 기준동저항 베타피크를 검출하는 일례를 설명하고자 도시한 그래프이다.3 is a conceptual diagram of a welding machine illustrating a process of measuring current and voltage in a resistance spot welding method according to an embodiment of the present invention, and FIG. 4 is a reference of a resistance spot welding method according to an embodiment of the present invention. It is a graph for explaining an example of detecting the reference dynamic resistance beta peak by the copper resistance detection step.

도 1, 도 3, 도 4를 참조하면, 본 발명의 일실시예에 따른 기준동저항 검출단계(S2)는, 기준용접 계측단계(S2-1), 동저항 산출단계(S2-2), 기준동저항 설정단계(S2-3)를 포함한다.1, 3, and 4, the reference dynamic resistance detection step S2 according to an embodiment of the present invention includes a reference welding measurement step S2-1, a copper resistance calculation step S2-2, Reference dynamic resistance setting step (S2-3) is included.

기준용접 계측단계(S2-1)에서는 기준용접조건(A')으로 정전류 제어 용접을 수행하면서 전류와 전압을 계측한다. 도 3에는 정전류 제어에 의해 저항 스폿 용접을 수행하면서 전극으로부터 전류와 전압을 계측할 수 있는 구성을 가지는 용접기의 모식도가 개시되어 있다. 도 3에 도시된 용접기에 의하면, 변압기를 통해 기준용접전류에 해당되는 정전류를 한 쌍의 전극에 인가하면서 기용접을 수행할 수 있고, 기용접 수행 시 전극에 걸리는 전압과 전류를 계측할 수 있다.In the reference welding measurement step (S2-1), current and voltage are measured while performing constant current control welding under the reference welding condition A ′. 3 shows a schematic diagram of a welder having a configuration capable of measuring current and voltage from an electrode while performing resistance spot welding by constant current control. According to the welding machine illustrated in FIG. 3, pre-welding may be performed while applying a constant current corresponding to the reference welding current to a pair of electrodes through a transformer, and the voltage and current applied to the electrode may be measured when performing pre-welding. .

동저항 산출단계(S2-2)에서는 기용접을 수행하는 동안 연속하여 계측된 전류(I)와 전압(V)으로부터 동저항을 산출한다. 동저항은 도 4의 그래프에 도시된 바와 같이 기준용접시간(tref) 동안 점차 감소되다가 증가하고 다시 감소되는 형태로 가변된다.In the dynamic resistance calculation step (S2-2), the copper resistance is calculated from the continuously measured current I and voltage V during pre-welding. As shown in the graph of FIG. 4, the copper resistance gradually decreases during the reference welding time t ref , and then increases and decreases again.

기준동저항 설정단계(S2-3)에서는 설정 용접시간 경과 후, 가장 큰 저항값을 기준동저항 베타피크(Bref)로서 설정한다. 설정 용접시간은 20~40ms로 설정할 수 있으며, 도 4에 도시된 그래프에 이를 적용하면 기준동저항 베타피크(Bref)는 220μΩ이 된다.In the reference dynamic resistance setting step S2-3, after the set welding time has elapsed, the largest resistance value is set as the reference dynamic resistance beta peak B ref . The set welding time can be set to 20 ~ 40ms, if applied to the graph shown in Figure 4 the reference dynamic resistance beta peak (B ref ) is 220μΩ.

기준입열량 설정단계(S3)에서 기준입열량(Qref)을 설정함에 있어서는, 기용접을 수행하면서 측정한 전류(I)와 전압(V), 기준용접시간(tref)을, 하기 [수학식 1]에 대입하여 산출할 수 있다.In setting the reference heat input Q ref in the reference heat input amount setting step S3, the current I, the voltage V, and the reference welding time t ref measured while performing pre-welding are given by It can calculate by substitution to Formula 1].

Figure 112018084735505-pat00003
Figure 112018084735505-pat00003

도 2의 표에는 용접전류(kA) 및 용접시간(ms)에 따른 입열량(J)이 정리되어 있으며, 수학식[1]에 의해 산출된 기준입열량(Qref)은, 즉 기준용접전류 7.5kA, 기준용접시간(tref) 410ms의 조건으로 용접을 수행하는 경우 용접부에 작용하는 입열량은, 도 2 상의 A'에 기록된 2121J이다. 참고로, < > 내에 기록된 수치는 전력값이다.In the table of FIG. 2, the heat input amount J according to the welding current kA and the welding time ms is summarized, and the reference heat input Q ref calculated by Equation [1] is a reference welding current. When welding is performed under a condition of 7.5 kA and a reference welding time (t ref ) 410 ms, the heat input applied to the weld portion is 2121J recorded in A ′ in FIG. 2. For reference, the numerical value recorded in <> is a power value.

도 5는 본 발명의 일실시예에 따른 저항 스폿 용접방법의 용접시간 제어단계에서 검출된 동저항을 기준동저항과 비교하여 설명하고자 도시한 그래프이고, 도 6은 도 5에 도시된 그래프 상의 동저항 베타피크를 기준동저항 베타피크와 수치로 비교하여 나타낸 표이며, 도 7은 본 발명의 일실시예에 따른 저항 스폿 용접방법의 용접시간 제어단계에 의해 조절된 용접시간을 기준용접시간과 비교하여 도시한 그래프이다.FIG. 5 is a graph illustrating the copper resistance detected in the welding time control step of the resistance spot welding method according to an embodiment of the present invention in comparison with the reference copper resistance, and FIG. 6 is a graph on the graph shown in FIG. 5. It is a table comparing the resistance beta peak with the reference dynamic resistance beta peak, Figure 7 is compared with the standard welding time the welding time adjusted by the welding time control step of the resistance spot welding method according to an embodiment of the present invention It is a graph shown.

도 1, 도 5, 도 6을 참조하면, 본 발명의 일실시예에 따른 용접시간 제어단계(S5)는, 동저항 검출단계(S5-1), 목표입열량 산출단계(S5-2), 입열량 비교단계(S5-3), 목표입열량 확보단계(S5-4), 본용접 종료단계(S5-5)를 포함한다.1, 5, and 6, the welding time control step (S5) according to an embodiment of the present invention, the dynamic resistance detection step (S5-1), the target heat input calculation step (S5-2), A heat input comparison step (S5-3), a target heat input secured step (S5-4), the main welding end step (S5-5).

동저항 검출단계(S5-1)에서는 기준용접조건(A')으로, 즉 기준용접조건 검출단계(S1)에서 검출, 선정된 기준용접전류와 기준용접시간(tref)의 조건으로, 본용접을 진행하면서, 기준동저항 검출단계(S2)에서와 동일하게 전류와 전압을 계측하는 과정을 거쳐 동저항 베타피크(Bweld)를 실시간으로 검출한다. In the dynamic resistance detecting step S5-1, the main welding is performed by the reference welding condition A ', that is, the condition of the reference welding current and the reference welding time t ref detected and selected in the reference welding condition detecting step S1. While proceeding, through the process of measuring the current and voltage as in the reference dynamic resistance detection step (S2) to detect the dynamic resistance beta peak (B weld ) in real time.

용접 환경(도금, 가압력, 모재 표면 상태, 용접점 간의 거리 등)이 변하지 않고 이상적으로 일정하게 유지되면, 기준동저항 검출단계(S2)에서 검출된 동저항과 본용접에서 검출되는 동저항은 동일한 형태를 가지게 된다. 그러나 용접 환경이 일정하지 않으면 본용접에서의 동저항은 도 5에 도시된 바와 같이 기준동저항 검출단계(S2)에서 검출된 동저항과 다른 형태를 가진다. 동저항 베타피크에 해당되는 저항의 작용에 의해 스폿 용접이 주요하게 이루어지게 되므로, 동저항 베타피크는 용접 환경에 따른 동저항의 변화를 검출하기 위한 지표로서 활용하기에 적합하다.If the welding environment (plating, pressing force, base metal surface state, distance between welding points, etc.) does not change and remains ideally constant, the copper resistance detected in the reference copper resistance detecting step (S2) and the copper resistance detected in the main welding are the same. Form. However, if the welding environment is not constant, the copper resistance in the main welding has a form different from the copper resistance detected in the reference copper resistance detecting step S2 as shown in FIG. 5. Since spot welding is mainly performed by the action of the resistance corresponding to the dynamic resistance beta peak, the dynamic resistance beta peak is suitable to be used as an index for detecting a change in the dynamic resistance according to the welding environment.

목표입열량 산출단계(S5-2)에서는 동저항 베타피크(Bweld)와 기준동저항 베타피크(Bref) 간의 비율(이하 '베타피크비'라 한다)과, 기준입열량(Qref)으로부터 목표입열량(Qtarget)을 산출한다. 목표입열량(Qtarget)은, 기준입열량(Qref), 기준동저항 베타피크(Bref), 동저항 베타피크(Bweld)를, 하기 [수학식 2]에 대입하여 산출할 수 있다.In the target heat input calculation step (S5-2), the ratio between the dynamic resistance beta peak (B weld ) and the reference dynamic resistance beta peak (B ref ) (hereinafter referred to as 'beta peak ratio') and the reference heat input quantity (Q ref ) The target heat input quantity Q target is calculated from. The target heat input Q target can be calculated by substituting the reference heat input Q ref , the reference dynamic resistance beta peak B ref , and the dynamic resistance beta peak B weld into Equation 2 below. .

Figure 112018084735505-pat00004
Figure 112018084735505-pat00004

도 5의 그래프에 의하면, 기준동저항 베타피크(Bref)와 동저항 베타피크(Bweld)가 도 6의 기재된 바와 같이 도출된다. 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 높은 경우(도 5 상의 동저항(HIGH) 곡선), 베타피크비는 1보다 작고, 따라서 목표입열량(Qtarget)은 기준입열량(Qref)보다 작아진다. 그리고, 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 낮은 경우(도 5 상의 동저항(LOW) 곡선), 베타피크비는 1보다 크고, 따라서 목표입열량(Qtarget)은 기준입열량(Qref)보다 커진다.According to the graph of FIG. 5, the reference dynamic resistance beta peak B ref and the copper resistance beta peak B weld are derived as described in FIG. 6. When the dynamic resistance beta peak (B weld ) is higher than the reference dynamic resistance beta peak (B ref ) (HIGH curve in FIG. 5), the beta peak ratio is smaller than 1, and thus the target heat input Q target is It becomes smaller than the reference heat input Q ref . In addition, when the dynamic resistance beta peak (B weld ) is lower than the reference dynamic resistance beta peak (B ref ) (the dynamic resistance (LOW) curve in FIG. 5), the beta peak ratio is larger than 1, and thus the target heat input (Q target). ) Is larger than the reference heat input Q ref .

입열량 비교단계(S5-3)에서는 본용접의 용접부에 작용하는 입열량과 목표입열량(Qtarget)을 실시간으로 비교한다. 목표입열량 확보단계(S5-4)에서는 본용접의 용접부에 작용하는 입열량이 목표입열량(Qtarget)에 도달되기까지 본용접을 지속한다. 본용접 종료단계(S5-5)에서는 용접부에 작용하는 입열량이 목표입열량(Qtarget)에 도달되면 본용접을 종료한다.In the heat input amount comparison step (S5-3), the heat input amount acting on the welded portion of the main welding and the target heat input Q target are compared in real time. In the target heat input securing step (S5-4), the main welding is continued until the heat input amount acting on the weld portion of the main welding reaches the target heat input Q target . In the main welding end step (S5-5), the main welding ends when the heat input amount acting on the welding portion reaches the target heat input Q target .

상기와 같은 구성을 가지는 본 발명에 따른 저항 스폿 용접방법에 의하면, 기준용접전류에 해당되는 정전류를 전극에 인가하며 본용접을 수행함에 있어서, 용접 환경에 맞추어 목표입열량(Qtarget)을 다르게 도출하고, 목표입열량(Qtarget)을 확보하기 위해 도 7에 도시된 바와 같이 용접시간을 가변시킴으로써, 입열량 과다 또는 입열량 미달로 인한 용접 품질 저하 및 용접 불량을 방지할 수 있다.According to the resistance spot welding method according to the present invention having the above configuration, in performing the main welding while applying a constant current corresponding to the reference welding current to the electrode, the target heat input (Q target ) is derived differently according to the welding environment And, by varying the welding time as shown in Figure 7 to secure the target heat input (Q target ), it is possible to prevent the welding quality deterioration and poor welding due to the excessive heat input or heat input is insufficient.

보다 구체적으로는, 본 발명에 의하면, 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 높은 경우, 베타피크비의 비율로, 기준입열량(Qref)보다 목표입열량(Qtarget)을 작게 설정함으로써, 본용접 시 입열량 과다로 인한 용접부 날림 현상 및 불량을 방지하고, 설정 강도 이상의 인장강도를 가지는 건전한 용접부를 생성할 수 있다.More specifically, according to the present invention, when the dynamic resistance beta peak (B weld ) is higher than the reference dynamic resistance beta peak (B ref ), it is a ratio of the beta peak ratio, the target heat input amount than the reference heat input (Q ref ) By setting (Q target ) small, it is possible to prevent the welding part flying phenomenon and defect due to excessive heat input during the main welding, and to generate a healthy weld part having a tensile strength of more than the set strength.

또한, 본 발명에 의하면, 동저항 베타피크(Bweld)가 기준동저항 베타피크(Bref) 보다 낮은 경우, 베타피크비의 비율로, 기준입열량(Qref)보다 목표입열량(Qtarget)을 크게 설정함으로써, 본용접 시 입열량 미달로 인한 너겟 축소 및 인장강도 저하를 방지하고, 설정 강도 이상의 인장강도를 가지는 건전한 용접부를 생성할 수 있다.Further, according to the present invention, when the dynamic resistance beta peak (B weld ) is lower than the reference dynamic resistance beta peak (B ref ), the ratio of the beta peak ratio, the target heat input (Q target ) than the reference heat input (Q ref ) By setting large), it is possible to prevent nugget shrinkage and tensile strength reduction due to insufficient heat input during the main welding, and to create a healthy weld having a tensile strength of more than the set strength.

Claims (6)

용접부의 인장강도가 기준강도 이상이 되는 기준용접전류와 기준용접시간을 검출하는 기준용접조건 검출단계;
상기 기준용접전류로 기(旣)용접을 수행하면서, 기준동저항 베타피크를 검출하는 기준동저항 검출단계;
상기 기준용접시간동안 기용접의 용접부에 작용한 입열량을 기준입열량으로서 설정하는 기준입열량 설정단계;
상기 기준용접전류로 본(本)용접을 개시하는 본용접 개시단계; 및
본용접을 수행하면서 동저항 베타피크를 검출하고, 상기 기준동저항 베타피크, 상기 기준입열량, 상기 동저항 베타피크로부터 목표입열량을 산출하며, 본용접의 용접부에 작용하는 입열량이 상기 목표입열량에 도달되기까지 용접을 지속하는 용접시간 제어단계;를 포함하는 것을 특징으로 하는 저항 스폿 용접방법.
A reference welding condition detecting step of detecting a reference welding current and a reference welding time at which the tensile strength of the weld portion is equal to or higher than the reference strength;
A reference dynamic resistance detecting step of detecting a reference dynamic resistance beta peak while performing preliminary welding with the reference welding current;
A reference heat input setting step of setting a heat input amount acting on the welding part of the pre-weld as the reference heat input amount during the reference welding time;
A main welding start step of starting main welding with the reference welding current; And
While performing the main welding, the copper resistance beta peak is detected, a target heat input is calculated from the reference copper resistance beta peak, the reference heat input amount, and the copper resistance beta peak, and the heat input amount acting on the welding part of the main welding is the target. Resistance spot welding method comprising a; welding time control step of continuing the welding until the heat input amount.
제1항에 있어서,
상기 기준용접조건 검출단계는,
용접전류와 용접시간을 가변시키며 기용접을 수행하는 시험용접단계;
상기 용접부의 인장강도가 기준강도 이상이면서, 소재의 날림이 발생되지 않는 용접전류와 용접시간 범위를 적정용접구간으로서 찾아내는 적정범위 검출단계; 및
상기 적정용접구간 내에서 상기 기준용접전류와 상기 기준용접시간을 선정하는 기준조건 선정단계;를 포함하는 것을 특징으로 하는 저항 스폿 용접방법.
The method of claim 1,
The reference welding condition detection step,
A test welding step of performing welding by varying a welding current and a welding time;
An appropriate range detecting step of finding a welding current and a welding time range in which the tensile strength of the weld portion is equal to or greater than the reference strength and the material does not fly, as a proper welding section; And
And a reference condition selecting step of selecting the reference welding current and the reference welding time within the proper welding section.
제1항에 있어서,
상기 기준동저항 검출단계는,
상기 기준용접조건으로 정전류 제어 용접을 수행하면서 전류와 전압을 계측하는 기준용접계측단계;
계측된 전류와 전압으로부터 동저항을 산출하는 동저항산출단계; 및
설정 용접시간 경과 후, 가장 큰 저항값을 상기 기준동저항 베타피크로서 설정하는 기준동저항설정단계;를 포함하는 것을 특징으로 하는 저항 스폿 용접방법.
The method of claim 1,
The reference dynamic resistance detection step,
A reference welding measurement step of measuring current and voltage while performing constant current controlled welding under the reference welding condition;
A copper resistance calculation step of calculating a copper resistance from the measured current and voltage; And
And a reference dynamic resistance setting step of setting the largest resistance value as the reference dynamic resistance beta peak after the set welding time has elapsed.
제1항에 있어서,
상기 기준입열량(Qref)은,
기용접을 수행하면서 측정한 전류(I)와 전압(V), 상기 기준용접시간(tref)을, 하기 식
Figure 112018084735505-pat00005

에 대입하여 산출되는 것을 특징으로 하는 저항 스폿 용접방법.
The method of claim 1,
The reference heat input amount Q ref is,
The current (I) and voltage (V) measured while performing pre-welding, and the reference welding time (t ref )
Figure 112018084735505-pat00005

A resistance spot welding method, characterized in that it is calculated by substitution.
제1항에 있어서,
상기 목표입열량(Qtarget)은,
상기 기준입열량(Qref), 상기 기준동저항 베타피크(Bref), 상기 동저항 베타피크(Bweld)를, 하기 식
Figure 112018084735505-pat00006

에 대입하여 산출되는 것을 특징으로 하는 저항 스폿 용접방법.
The method of claim 1,
The target heat input amount Q target ,
The reference heat input (Q ref ), the reference dynamic resistance beta peak (B ref ), the dynamic resistance beta peak (B weld ), the following formula
Figure 112018084735505-pat00006

A resistance spot welding method, characterized in that it is calculated by substitution.
제1항에 있어서,
상기 용접시간 제어단계는,
본용접을 진행하면서 상기 동저항 베타피크를 검출하는 동저항 검출단계;
상기 동저항 베타피크와 상기 기준동저항 베타피크 간의 비율과, 상기 기준입열량으로부터 목표입열량을 산출하는 목표입열량 산출단계;
본용접의 용접부에 작용하는 입열량과 목표입열량을 실시간으로 비교하는 입열량 비교단계;
본용접의 용접부에 작용하는 입열량이 상기 목표입열량에 도달되기까지 본용접을 지속하는 목표입열량 확보단계; 및
상기 용접부에 작용하는 입열량이 상기 목표입열량에 도달되면 본용접을 종료하는 본용접 종료단계;를 포함하는 것을 특징으로 하는 저항 스폿 용접방법.The method of claim 1,
The welding time control step,
Dynamic resistance detecting step of detecting the dynamic resistance beta peak while the main welding;
A target heat input calculating step of calculating a target heat input amount from the ratio between the copper resistance beta peak and the reference copper resistance beta peak and the reference heat input amount;
A heat input comparing step of comparing a heat input amount acting on the welded portion of the main welding with a target input heat value in real time;
Securing a target heat input amount for continuing the main welding until the heat input amount acting on the welded portion of the main welding reaches the target heat input value; And
And a main welding end step of terminating the main welding when the heat input amount acting on the welding portion reaches the target heat input amount.
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