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目前,我国矿山使用的硬质合金钎头,大多数采用高频感应焊接,也有少数采用真空电阻炉和辐射加热电阻炉焊接的。用上述方法焊接的钎头,其焊缝都存在着不同程度的开裂现象和空洞等缺陷。焊缝开裂的主要原因是由于硬质合金片和钎头壳体钢材的线膨胀系数不同所引起的。当焊接加热时,硬质合金片和钢体都能自由膨胀,在焊后冷却收缩过程中,钢体要比硬质合金片收缩量大,因此它们之间产生了收缩差。如φ40毫米一字型钎头的焊缝收缩差达0.16毫米。该收缩差,除了靠极薄的焊缝塑性来抵消一小部分外,绝大部分以应力状态存在着。这种应力对焊缝是拉应力。当这个力大于焊缝连接强度时,焊缝就会开裂,严重地影响焊缝质量。导致钎头在凿岩过程中,硬质合金片的脱落或碎片,造成钎头早期报废。为了提高真空紫铜焊接硬质合金钎头的
At present, most of the hard alloy brazing heads used in mines in our country are made of high-frequency induction welding, and a few of them are welded with vacuum resistance furnace and radiant heating resistance furnace. With the above method of welding bit, the weld there are varying degrees of cracking and holes and other defects. The main reason for weld cracking is due to the difference in linear expansion coefficient between the cemented carbide piece and the brazing head shell steel. When welding heats up, both the cemented carbide piece and the steel body freely expand. During cooling and shrinking after welding, the steel body shrinks more than the cemented carbide piece, so that there is a difference in shrinkage between them. Such as φ 40 mm bit of the solder joint shrinkage difference of 0.16 mm. The shrinkage, in addition to plastic by a very thin weld to offset a small part, the vast majority of stress exists. This stress on the weld is tensile stress. When this force is greater than the weld joint strength, the weld will crack, seriously affecting the weld quality. As a result, during the rock drilling process, the bit of cemented carbide flakes off or fragments, causing the bit to scrap early. In order to improve the welding of vacuum brazing carbide brazing head