焊接速度增加时焊缝厚度和宽度，焊接速度与焊缝质量的关系

焊接速度增加时焊缝厚度和宽度，焊接速度与焊缝质量的关系结晶阶段Moreover the longer the edge of the heated tube blank is exposed to the air that is the slower the welding speed the deeper the non-metallic oxide will be produced. These deep non-metallic oxides are difficult to be completely extruded out of the weld in the subsequent extrusion crystallization process. After crystallization they will remain in the weld in the form of non-metallic inclusi

焊接速度与焊缝质量的关系应辩证地理解，不可忽视。主要体现在加热阶段和结晶阶段。

The relationship between welding speed and weld quality should be understood dialectically and cannot be ignored. It is mainly reflected in the Heating stage and Crystallization stage.

加热阶段

Heating stage

高频直缝焊管工况下，管坯边缘从室温加热到焊接温度，在此过程中管坯边缘完全暴露在空气中，没有任何保护，必然与空气中的氧和氮发生激烈反应，导致焊缝中的氮和氧化物显著增加。据测定，焊缝中氮含量增加20-45倍，氧含量增加7-35倍。同时，大量对焊缝有益的锰、碳等合金元素被燃烧蒸发，导致焊缝力学性能降低。因此，从这个意义上说，焊接速度越慢，焊缝质量越差。

Under the working condition of high-frequency Longitudinal Welded Pipe the edge of the pipe blank is heated from room temperature to welding temperature. In this process the edge of the pipe blank is completely exposed to the air without any protection. It is bound to react violently with oxygen and nitrogen in the air resulting in a significant increase in nitrogen and oxides in the weld. According to the measurement the nitrogen content in the weld increases by 20-45 times and the oxygen content increases by 7-35 times. At the same time a large number of manganese carbon and other alloy elements beneficial to the weld are burned and evaporated resulting in the reduction of the mechanical properties of the weld. Therefore in this sense the slower the welding speed the worse the weld quality.

不仅如此，加热后的管坯边缘暴露在空气中的时间越长，即焊接速度越慢，就会产生越深的非金属氧化物。这些深层非金属氧化物在后续的挤压结晶过程中很难被完全挤出焊缝，结晶后会以非金属夹杂物的形式残留在焊缝中，形成明显的脆性界面，从而破坏焊缝微观组织的连续性，降低焊缝强度。但焊接速度快，氧化时间短，生成的非金属氧化物少且只限于表层，所以在后续挤压过程中容易被挤出焊缝，焊缝中不会有太多的非金属氧化物残留，所以焊缝强度高。

Moreover the longer the edge of the heated tube blank is exposed to the air that is the slower the welding speed the deeper the non-metallic oxide will be produced. These deep non-metallic oxides are difficult to be completely extruded out of the weld in the subsequent extrusion crystallization process. After crystallization they will remain in the weld in the form of non-metallic inclusions forming an obvious brittle interface thereby destroying the continuity of the weld microstructure and reducing the weld strength. However the welding speed is fast the oxidation time is short and the generated non-metallic oxides are few and limited to the surface layer so it is easy to be extruded out of the weld in the subsequent extrusion process and there will not be too many non-metallic oxides left in the weld so the weld strength is high.

结晶阶段

crystallization stage

根据金属学原理，为了获得高强度焊缝，必须使焊缝显微组织的晶粒尽可能细小。提炼的基本方式是在短时间内形成足够多的晶核，使它们在显著长大之前相互接触，然后结晶过程结束。这就要求通过提高焊接速度，使焊缝快速离开加热区，使焊缝在较大的过冷度下快速结晶；当过冷度增大时，形核率可以大大提高，生长速率略有增加，从而达到细化焊缝晶粒的目的。

According to the principle of metallography in order to obtain high-strength weld the grain of weld microstructure must be as small as possible. The basic way of refining is to form enough crystal nuclei in a short time so that they contact each other before significant growth and then the crystallization process ends. This requires that by increasing the welding speed the weld can leave the heating zone quickly and the weld can crystallize rapidly under a large undercooling; When the undercooling degree increases the nucleation rate can be greatly improved and the growth rate increases slightly so as to achieve the purpose of refining the weld grain.

因此，在满足基本焊接条件的前提下，无论是焊接过程的加热阶段还是焊后冷却阶段，焊接速度越快，焊缝质量越好。

Therefore on the premise of meeting the basic welding conditions the faster the welding speed is the better the weld quality is whether it is the heating stage or the cooling stage after welding.