直缝焊管是通过高频焊接机组或者是通过埋弧焊机组焊接而成。高频焊接直缝焊管国内目前可生产范围：口径10-711mm厚度3-25mm。埋弧焊直缝焊管可生产范围，口径：325-1420mm厚度8-25mm。直缝焊管工艺简单，生产速度快所以它在城市建设，钢构工程，输气工程和供排水工程建设方面起着不可替代的作用。所以选择好优质的直缝焊管是保证工程安全顺利进行的必要因素。
Longitudinal welded pipe is welded by high frequency welding machine or submerged arc welding machine. At present, the domestic production range of high frequency welded straight seam welded pipe is 10-711mm in diameter and 3-25mm in thickness. Submerged arc welding straight seam welded pipe can be produced in a range of sizes: 325-1420 mm thick 8-25 mm. Longitudinal welded pipe has simple technology and fast production speed, so it plays an irreplaceable role in urban construction, steel structure engineering, gas transmission engineering and water supply and drainage engineering construction. Therefore, the selection of high quality straight seam welded pipe is a necessary factor to ensure the safe and smooth operation of the project. 在选择直缝焊管的时候第一我们要注意材质，一般直缝焊管的材质有Q235,16Mn，和L245等等，在我们验货的时候首先要确定材质是否合格。第二要看看直缝焊管的壁厚，是否达到要求的壁厚。公差是否在国家要求范围之内。第三要看焊管表面情况，是否有锈，锈的程度，一般黄锈没有问题，一般黄锈都是一层浮锈，红锈稍微严重一点。
When choosing straight seam welded pipe, we should first pay attention to the material quality. Generally, the material of straight seam welded pipe is Q235, 16Mn, L245 and so on. When we inspect the goods, we should first determine whether the material is qualified. The second is to see whether the wall thickness of the longitudinal welded pipe meets the required wall thickness. Is tolerance within the scope of national requirements? Third, it depends on the surface condition of welded pipe, whether there is rust or not, the degree of rust, general yellow rust is no problem, general yellow rust is a layer of floating rust, red rust slightly more serious.
但是退火过后也可以在一些不是很严格的项目上使用，但是如果是黑锈，说明这管子就只能卖废铁了。还有我们要看一下焊管表面是否有由，因为直缝焊管在生产过程中在机组上有可能会沾染油渍，最后我们要看管子两头的断面情况是否是圆面还是有挤压不规整。还要看下是否有毛刺。经过以上几种严格的检测手段如果焊管都通过，那么说明管子是合格的。
But after annealing, it can also be used in some less stringent projects, but if it is black rust, it means that the pipe can only sell scrap iron. Also, we need to see if there is any reason for the surface of the welded pipe, because the longitudinal welded pipe may be contaminated with oil stains on the unit during the production process. Finally, we need to see whether the cross-section of both ends of the pipe is round or irregular extrusion. It also depends on whether there are burrs. After the above several strict testing methods, if the welded pipe passes, then the pipe is qualified.
