直縫方管機將帶(dai)鋼送(song)入焊(han)(han)管機(ji)組，經(jing)多道(dao)軋輥(gun)滾(gun)壓(ya)(ya)，帶(dai)鋼逐漸(jian)卷(juan)起，形(xing)成有開口間(jian)(jian)隙(xi)的圓形(xing)管坯，調整擠壓(ya)(ya)輥(gun)的壓(ya)(ya)下量(liang)，使焊(han)(han)縫(feng)間(jian)(jian)隙(xi)控制(zhi)在1~3mm，并使焊(han)(han)口兩端(duan)齊平。如間(jian)(jian)隙(xi)過(guo)(guo)大，則造(zao)成鄰(lin)近效應減少，渦流熱量(liang)不足，焊(han)(han)縫(feng)晶間(jian)(jian)接(jie)合不良(liang)而產生(sheng)未熔(rong)合或開裂。如間(jian)(jian)隙(xi)過(guo)(guo)小則造(zao)成鄰(lin)近效應增大，焊(han)(han)接(jie)熱量(liang)過(guo)(guo)大，造(zao)成焊(han)(han)縫(feng)燒損;或者焊(han)(han)縫(feng)經(jing)擠壓(ya)(ya)、滾(gun)壓(ya)(ya)后形(xing)成深坑，影響(xiang)焊(han)(han)縫(feng)表面(mian)質(zhi)量(liang)。
方管機(ji)的(de)焊接溫(wen)度主要受高頻(pin)渦(wo)流熱功(gong)率(lv)(lv)(lv)的(de)影(ying)響，高頻(pin)渦(wo)流熱功(gong)率(lv)(lv)(lv)主要受電(dian)(dian)(dian)(dian)流頻(pin)率(lv)(lv)(lv)的(de)影(ying)響，渦(wo)流熱功(gong)率(lv)(lv)(lv)與電(dian)(dian)(dian)(dian)流激勵頻(pin)率(lv)(lv)(lv)的(de)平方成正比;而電(dian)(dian)(dian)(dian)流激勵頻(pin)率(lv)(lv)(lv)又受激勵電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流和電(dian)(dian)(dian)(dian)容、電(dian)(dian)(dian)(dian)感的(de)影(ying)響。
直縫(feng)方管機組上(shang)式可知，激勵(li)頻率(lv)(lv)與激勵(li)回(hui)(hui)路(lu)中(zhong)的電(dian)(dian)(dian)容、電(dian)(dian)(dian)感平(ping)方根成反比(bi)、或(huo)者(zhe)與電(dian)(dian)(dian)壓、電(dian)(dian)(dian)流的平(ping)方根成正比(bi)，只(zhi)要改變回(hui)(hui)路(lu)中(zhong)的電(dian)(dian)(dian)容、電(dian)(dian)(dian)感或(huo)電(dian)(dian)(dian)壓、電(dian)(dian)(dian)流即(ji)可改變激勵(li)頻率(lv)(lv)的大(da)小(xiao)，從而達到控制焊接溫(wen)度(du)的目的。對于低碳鋼(gang)，焊接溫(wen)度(du)控制在(zai)1250~1460℃，可滿足管壁厚3~5mm焊透要求(qiu)。另外，焊接溫(wen)度(du)亦可通(tong)過(guo)調節焊接速度(du)來實現。
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