Surface quality problems of steel pipe mainly shows in the surface oxide thick,surface cracking,surface re-skin, surface mechanical pumps and so on.After the completion of hot-rolled carbon steel cold rolled steel and then heat treatment or after, it will form a thick and strong adhesion, high temperature oxide.Not only the existence of oxide steel looks poor quality, also affects the use of steel, which is not allowed by the standard. Such oxides with the general sandblasted are difficult to remove, to use pickling or mechanical polishing method to clear.
Surface cracking occurred in the hot-rolled steel,a common carbon steel and alloy steel tubes, mainly due to rapid cooling process huge surface tension caused by the residual stress caused and after.Cracks do not belong to surface cracking (no trauma), but with some characteristics of cracks are formed in the notch sensitivity effect in many application conditions (such as high temperature, low temperature,environmental stress corrosion cracking.etc.)to a certain extent,so that reduce the life of the steel pipe.and even lead to pipe failure.
Therefore, the former steel factory must crack down cleared.Heavy leather surface is common in cold-rolled or cold drawn steel tubes, mainly due to the billet surface or abrasive caused no deal.Heavy presence will affect the appearance of the skin quality steel the impact on the use of steel pipe and crack.though not serious. but in some places still have some impact. Improved by strengthening production management, improve and control the quality of the billet surface quality and abrasive.Mechanical bruise is a part of the most ordinary quality problems,mainly produced in the production, handling and transportation.Steel will form a bruise on structural discontinuities, use is a source of stress concentration,but also generate notch sensitivity.Compared with cracks, mechanical defects bruised clear outline, without involving internal injuries metal, thus allowing some of the bumps standard depth exist, but in some of the more sensitive the application conditions, the depth exceeds a certain value, or bumps, should be ground to eliminate so smooth transition.
Size deviation mainly in steel pipe straightness,roundness,uneven thickness aspect.In most cases,the straightness tolerance for the use of large steel tube, but the straightness of the steel pipe manufacturing standards set forth requirements, if the specified value is exceeded would constitute a reason to return, and therefore,the plant should still be noted.Roundness tolerance will affect the use of steel pipes.
mainly in the group of the welding head on the wrong side.Their roundness tolerance wrong side due to bear capacity of welded joints will not only reduce, but also produce stress concentration.Group on the scene, some pipe roundness can be corrected. Outside diameter steel pipe is used for the impact bias and roundness tolerance fairly.Non-uniform wall thickness is generally easy to ignore, and many steel pipe standards are not clearly defined. If severe uneven wall thickness, will not only result set to the wrong side of the joint, but also on secondary deformation processing (such as steel pipe manufacturing pipe fittings) adversely affected.
Post time: Aug-09-2023