Profile for Mild steel & High Tensile Steel

1.Base metal introduction:

A steel is type of Carbon 0.02%~2%. Usually compound with Manganese and Silicon element.

Mild Steel and 490 N/mm² high tensile steel were common use for welding categories. Choose appropriate steel and following welding consumables supplier’s suggestion to meet construction specification demands in standard line.

2. Welding method and Specifications:

Welding could carry out the joint issue between steel plates. Therefore the base metal would be diffused from once or multiple times heat treatment. The welding efficiency would be effected with following reasons:

2.1 Carbon equivalent from base metal:

In order to keep low diffusible from heat affected zone (HAZ), please make ensure specification from base metal, welding method and process. We usually use two types of formula for Carbon equivalent indications:

Ceq (JIS) = C + 1/6Mn + 1/24Si + 1/40Ni + 1/5Cr + 1/4Mo + 1/14V  (%)

CE (IIW) = C + Mn/6 + (Ni+Cu)/15 + (Cr+Mo+V)/5  (%)

In the cooling process after welding, the toughness of the HAZ is

. In the cooling process after welding, the hardness of the HAZ is limited austenite grains. But the HAZ hardness value would be increased on Medium-High carbon steel, High tensile steel or Low alloy steel metal.

In accordance with International Welding Society, the hardness value over than HV350 might be caused crack.

2.2 Workpiece constraint and restraint:

The welding metal expansion and contraction by temperature. Lean workpiece would be getting more value than thick one. This phenomenon so called constraint and restraint.

Constraint (K) = constraint degree (K0) x workpiece thickness (t) (kg/mm *mm)

K=constraint degree

T= workpiece thickness

Constraint value, joint design and welding method were related with workpiece thickness. The value getting higher might caused crack.

2.3 Diffusible hydrogen effect:

Hydrogen content had been caused by flux, base metal surface and surrounding circumstance moisture. When hydrogen keep maintain and growing would be caused crack issue.

2.4 Temperature management:

The workpiece temperature, interpass welding temperature, input control or PWHT management main target is stress relieving. Due to that, temperature control recommend to follow up design and construction specification, WPS and welding classification standard.

2.5 Rare element effect:

In order to avoid crack or porosity defect, we recommend keep P, S, Cu, B, O element content as low as possible. Those element would be affected welding bead quality from base metal.