자동차용 고강도 강판의 저항 점용접 시 다단통전이 너깃 형성에 미치는 영향

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저항 점용접,다단통전,Pre-pulse,RSW
With the fast advanced auto industry, prompt and reliable welding processes are required. In more than 90 percent, resistance spot welding process is applied to car body manufacturers.
According to the international environment regulations, in the automobile industry, improvement of fuel efficiency became a hot topic and the introduction of high strength steel is accelerated.
Based on 2014 developmet of car body, the rate of high strength steel is about 53 percent of total panels of car body.
In the high strength steel, increasing alloying elements makes interfacial resistance high and it makes differences of the resistance in between multi layers(more than 3 layers). Because of this reason, imperfect nuggets are builded and bond strengths are lowered.
For this reason, there are needs for derivation of optimum welding process different from existing methods. In this paper, observe and examine the short-intensive pre-pulse welding mechanism through the providing existing car body parts.

The method of observing the cross section of the nugget is that cut the center of the nugget, treat the acid and analyze with the optical microscope.
The result of applying short-intensive pre-pulse shows that the nugget size of 3 layers welding sheets is about 18% bigger than before and 4 layers welding sheets is about 57% larger than before in contact surface with high-strength steel sheet.
Targeting the QTR INR_LH part of the car body in production, after sorting the all spot welding points of 3 and 4 layers welding sheets, research the growth of the nugget size which are applied with the short-intensive pre-pulse 120~140% of the main pulse. As the result, Nugget size looks like bigger than before and 4 layer welding sheets are more efficent than 3 layer welding sheets.
In many cases, the car body is composed of thin iron plate and there are cooling effects and radiation effects when spot welding is going hence there are difficulty building the nugget size. But in these cases, applying of the short-intensive pre-pulse make sure that the nugget size growed.
Alternative Title
The Influence of Multi Pulse Currents on Nugget Formation of Automotive High Strength Steel in RSW
Alternative Author(s)
Ko, Eun Hyung
일반대학원 용접·접학과학공학
Awarded Date
Table Of Contents

제 1 장. 서 론 1
1 . 1 연구배경 및 목적 1
1 . 2 연구현황 및 내용 5

제 2 장. 용접이론 6
2 . 1 저항 점용접의 원리 및 특징 6
2.1.1 저항 점용접의 원리 6
2.1.2 저항 점용접의 주요인자 8
2.1.3 저항 점용접의 용접공정 11
2.1.4 다단통전 & 적응제어 모드 12

2 . 2 용접성 평가 방법 14
2.2.1 파괴 및 비파괴 검사, 인장시험 14
2.2.2 너깃절단 및 광학현미경 분석 16

제 3 장. 초고장력강의 용접특성 18
3 . 1 초고장력강의 성부에 따른 용접 특성(문제점) 18
3.1.1 화학적 성질 18
3.1.2 물리적 성질 18
3.1.3 용접 특성 19

3 . 2 저항 점용접 적용방안 20

제 4 장. 실험 및 결과 21
4 . 1 실험 조건 및 구성 21

4 . 2 1차 실험 세부내용 및 결과 22
4.2.1 1차 실험 목적 및 세부사항 22
4.2.2 시편의 구성 및 용접 조건 23
4.2.3 1차 실험결과 24

4 . 3 2차 실험 세부내용 및 결과 26
4.3.1 2차 실험 배경 26
4.3.2 2차 실험 목적 및 세부사항 27
4.3.3 2차 실험 결과 / 분석 29

4 . 4 2차 실험 종합 31
4.4.1 2차 실험(3매 용접부) 결과 / 분석 31
4.4.2 2차 실험(4매 용접부) 결과 / 분석 34

4 . 5 3차 실험 세부내용 및 결과 36
4.5.1 실험 목적 및 세부사항 36
4.5.2 3차 실험 결과 / 분석 38

4 . 6 3차 실험 종합 40
4.6.1 3차 실험(3매 용접부) 결과 / 분석 40
4.6.2 3차 실험(4매 용접부) 결과 / 분석 46

제 5 장. 결론 48

Reference 50
고은형. (2016). 자동차용 고강도 강판의 저항 점용접 시 다단통전이 너깃 형성에 미치는 영향.
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