What is the Difference Between 316 and 316L

       

As we all know, 316L is a stainless steel grade.  AISI 316L is the corresponding American grade, and SUS 316L is the corresponding Japanese grade. The Chinese standard brand is 022cr17ni12mo2 (new standard), and the old brand is 00Cr17Ni14Mo2, which indicates that it mainly contains Cr, Ni and Mo. The number indicates the approximate percentage. Let's first look at the chemical composition of 316 and 316L.

We can see that the carbon content of 316L is lower and has better corrosion resistance.

1 welding method of stainless steel pipes

Because most of the stainless steel pipes are of different sizes, according to the welding characteristics of stainless steel, the heat input is minimized, so manual arc welding and argon arc welding are adopted.

For pipe diameter greater than 159 mm, argon arc welding shall be used for bottom drilling and manual arc welding cover. All argon arc welding with diameter less than 159mm.

 

2 welding materials

Austenitic stainless steel is a special performance steel. In order to meet the same performance of the joint, the welding material should be selected according to the principle of "equal composition". At the same time, h00cr19ni12mo2 welding wire for argon arc welding and chso22 welding rod for manual arc welding should be selected as the filler material to enhance the resistance to hot crack and intergranular corrosion and make a small amount of ferrite appear in the joint.

3 welding parameters

The outstanding characteristic of austenitic stainless steel is sensitive to overheat, so small current and fast welding are adopted. The interlayer temperature should be strictly controlled during multi-layer welding, so that the interlayer temperature is less than 60 ℃.

4 groove form and assembly positioning welding

The V-shaped groove is used as the groove form. Due to the small welding current and small penetration, the blunt edge of the groove is smaller than that of carbon steel, about 0-0.5mm, and the groove angle is larger than that of carbon steel, about 65 °- seven hundred °。

 Due to the large thermal expansion coefficient of stainless steel, the welding stress is large during welding, so the strict positioning welding is required. For D ≤ Φ 89mm pipe is positioned by two points, D= Φ 89- Φ Three point positioning is used for 219mm, and four point positioning is used for D ≥ 219mm; The length of tack weld is 6-8mm.

 

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