直縫方管機將帶(dai)鋼送入焊(han)(han)(han)管(guan)機組，經(jing)多道軋輥(gun)滾壓(ya)，帶(dai)鋼逐漸(jian)卷起，形成(cheng)(cheng)有開(kai)口間(jian)(jian)隙的圓(yuan)形管(guan)坯，調整(zheng)擠(ji)壓(ya)輥(gun)的壓(ya)下量(liang)(liang)，使(shi)焊(han)(han)(han)縫(feng)(feng)間(jian)(jian)隙控制在1~3mm，并(bing)使(shi)焊(han)(han)(han)口兩(liang)端齊平(ping)。如(ru)(ru)間(jian)(jian)隙過大，則造成(cheng)(cheng)鄰近效應減少(shao)，渦(wo)流熱量(liang)(liang)不(bu)足，焊(han)(han)(han)縫(feng)(feng)晶間(jian)(jian)接(jie)合不(bu)良(liang)而產生(sheng)未熔合或(huo)開(kai)裂。如(ru)(ru)間(jian)(jian)隙過小(xiao)則造成(cheng)(cheng)鄰近效應增大，焊(han)(han)(han)接(jie)熱量(liang)(liang)過大，造成(cheng)(cheng)焊(han)(han)(han)縫(feng)(feng)燒損;或(huo)者焊(han)(han)(han)縫(feng)(feng)經(jing)擠(ji)壓(ya)、滾壓(ya)后形成(cheng)(cheng)深坑，影響焊(han)(han)(han)縫(feng)(feng)表(biao)面質(zhi)量(liang)(liang)。
方(fang)管(guan)機(ji)的(de)焊接溫度主要受(shou)高(gao)頻渦(wo)(wo)流(liu)熱功率(lv)(lv)的(de)影響，高(gao)頻渦(wo)(wo)流(liu)熱功率(lv)(lv)主要受(shou)電(dian)(dian)(dian)(dian)流(liu)頻率(lv)(lv)的(de)影響，渦(wo)(wo)流(liu)熱功率(lv)(lv)與電(dian)(dian)(dian)(dian)流(liu)激勵(li)頻率(lv)(lv)的(de)平方(fang)成正比;而電(dian)(dian)(dian)(dian)流(liu)激勵(li)頻率(lv)(lv)又受(shou)激勵(li)電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流(liu)和電(dian)(dian)(dian)(dian)容、電(dian)(dian)(dian)(dian)感的(de)影響。
直縫方管(guan)機組(zu)上式可(ke)(ke)知，激勵(li)(li)頻(pin)(pin)率與(yu)激勵(li)(li)回(hui)路中的(de)電(dian)(dian)容、電(dian)(dian)感平(ping)方根(gen)成反(fan)比、或者與(yu)電(dian)(dian)壓(ya)、電(dian)(dian)流的(de)平(ping)方根(gen)成正比，只(zhi)要改變回(hui)路中的(de)電(dian)(dian)容、電(dian)(dian)感或電(dian)(dian)壓(ya)、電(dian)(dian)流即可(ke)(ke)改變激勵(li)(li)頻(pin)(pin)率的(de)大(da)小，從而達到(dao)控制(zhi)焊(han)接(jie)溫度的(de)目的(de)。對(dui)于(yu)低碳鋼，焊(han)接(jie)溫度控制(zhi)在(zai)1250~1460℃，可(ke)(ke)滿足(zu)管(guan)壁(bi)厚3~5mm焊(han)透要求。另外，焊(han)接(jie)溫度亦可(ke)(ke)通(tong)過調節(jie)焊(han)接(jie)速度來實(shi)現。
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