What are the problems that will occur in oCr18Ni9Ti welding?

It is easy to appear intergranular corrosion in the weld area, which is mainly caused by intergranular cr poverty, which can be avoided as long as the appropriate electrode is matched to make the weld ultra-low-carbon; The knife-like corrosion in the fusion zone is also caused by poor CR; stress corrosion cracking, which is caused by the segregation of alloying elements; There is also thermal cracking, mainly caused by thermal conductivity and linear expansion coefficient, and there is attention to the formation of columnar crystals when congenetic crystallization, as long as the solidification mode is controlled, generally the weld can be inhibited by austenite + ferrite duplex structure.

It's hard to come up with a problem with this material, so you can rest assured that you can weld it, using 308 welding wire or 102 electrode.

OCR18NI9TI is an austenitic stainless steel with good weldability If it is welded with China Steel, it is generally used 18-8 type stainless steel electrode on the line E-308 for welding rod, and A102 for welding wire If it is dissimilar steel welding, the main consideration is that the chemical composition of the weld is not diluted Both to ensure that the content of Cr and Ni is used for steel welding such as E309 and 16Mn steel, and H1Cr24Ni13 for welding wire, when selecting welding materials, it is necessary to determine according to the Schaefler phase diagram and fusion ratio to ensure that the weld structure contains 5 10% The δ of ferrite because a small amount of ferrite can resist crack propagation and intergranular corrosion. Stainless steel welding does not require preheating and post-heat treatment. Hopefully, it's best to add a few extra points (*hee-hee-hee......

Summary. 1. Stainless steel welding electrode E308 should be used for stainless steel welding.

2. Covered electrode melts the metal strip filled at the joint of the welded workpiece during gas welding or electric welding. It is composed of two parts: coating and welding core. It is melted by the coating and added to the weld as a filler metal, becoming the main component of the weld metal, and such a substance is called a welding rod.

What welding wire should be used for 1Cr18Ni9Ti and 1Cr18Ni9Ti welding, talk about it in detail.

1. Stainless steel welding should be used to weld the metal strip filled in the joint of the welded workpiece during gas welding or electric welding. It is composed of two parts: coating and welding core. It is melted by the coating and added to the weld as a filler metal, becoming the main component of the weld metal, and such a substance is called a welding rod.

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Weldability of 1Cr18Ni9Ti.

In general, stainless steel has good plasticity, but in hot or cold working improperly, embrittlement and crack will be formed, the alloying elements in stainless steel have a strong affinity for oxygen, so it is also easy to produce the burning loss of alloying elements, in addition there is also the sensitivity of cracking heat to the grain, with the development of technology and the understanding of this type of steel, these problems can be solved in technology (the selection of welding materials, the formulation of welding process specifications, the adoption of welding measures, the selection of equipment). Therefore, the following mainly discusses the solution of the intergranular corrosion problem of this type of steel welded joint.

When 1Cr18Ni9Ti steel is welded, the intergranular corrosion of the weld can be taken from the following aspects:

1. A certain amount of ferrite-forming elements are added to the weld, such as titanium, niobium, molybdenum, barium, silicon, etc., to promote the formation of austenite and ferrite duplex structure in the weld. It has been proved that the presence of a small amount of ferrite in austenite will greatly improve the resistance of the material to intergranular corrosion. This is because the concentration of carbon in austenite is greater than that in ferrite, so the carbon atom has a tendency to diffuse into the austenite.

The carbon in austenite and chromium in ferrite are at the junction of two phases to form chromium carbide, and because the diffusion rate of chromium in ferrite is much faster than that in austenite, once the chromium-poor region is formed at the grain boundary, it can be replenished from the ferrite relatively quickly, so that the chromium-poor layer disappears.

However, the amount of ferrite in 1Cr18Ni9Ti should not be too much, otherwise it will promote phase formation and reduce the ability to resist intergranular corrosion.

2. Stable carbide elements are added to the weld, that is, titanium and niobium are added to the weld to form TIC or NBC, reduce the possibility of forming chromium carbide, and can also avoid intergranular corrosion, such as Ao 132 electrode, Ao 137 electrode is a stainless steel electrode with niobium as a stabilizer.

3. Reducing the carbon content in the weld can reduce and avoid the formation of carbides, which will lead to the formation of intergranular corrosion. If the carbon content is reduced to less, carbide precipitation can be avoided. This type of stainless steel or electrode with a lower carbon content, commonly referred to as "ultra-low-carbon" stainless steel, can effectively overcome intergranular corrosion.

4.For welded joints, it is common to control the welding specification or use post-weld heat treatment to improve the resistance to intergranular corrosion.

The measures to control the welding thermal specification are mainly to shorten the heating time, reduce the weld cross-section, weld with small line energy specifications, force rapid cooling, etc., to avoid excessive residence time at dangerous temperatures.

Post-welding heat treatment, can be stabilized annealing, both heated to 850 heat preservation for 4h, and then air cooling, can also use solution treatment, both generally heated to 1050-1150, water cooling after heat preservation, can avoid intergranular corrosion.

Groove and nearby base metal to clean oil, water, oxide layer, etc.; TIG welding needs back protection to protect gas purity and flow; control of heat input; Pay attention to interlayer cleaning and weld seam forming, etc., these are the basics, of course, the selection of the right welding consumables is a must.

1Cr18Ni9Ti is a common stainless steel (SUS321) with an austenitic tissue type. 1Cr18Ni9Ti represents the content of chromium (%), nickel (%), respectively. It is a stainless steel material grade in China.

It is used to make acid-resistant containers and equipment linings, anti-magnetic instruments, and medical devices, and has good intergranular corrosion resistance.

Chemical composition. Carbon C:

Silicon si:.

Manganese mn: .

Sulfur s:

Phosphorus p:

Chromium cr:.

Nickel ni:.

Titanium ti: 5(.

The weldability is good, the welding method that can be used depends on the wall thickness, the thickness is within 2mm of the work should be argon arc welding, medium and thick plates can be used manual arc welding and submerged arc automatic welding, there will be no knife edge makeup corrosion after welding, and the mechanical properties of the weld metal are 510MPa 35%.

Austenitic stainless steel, good weldability, the welding method that can be used depends on the wall thickness, the thickness of the work within 2mm should be argon arc welding, medium and thick plates can be used manual arc welding and submerged arc automatic welding, there will be no knife edge corrosion after welding, and the mechanical properties of the weld metal are 510MPa 35%.

Equivalent to 304L, and 0Cr18Ni9Ti304 The difference is that the carbon content is low, which is more common and basic in austenitic stainless steel, there are no special requirements for welding, the key is to select the welding consumables, and the base metal must also be qualified products. In addition, it is well known that stainless steel welding should control the line energy input, that is, not too much current, but also control the interlayer temperature, etc., and finally stainless steel welding is easy to contain slag, which is related to the acidity and alkalinity of the coating, so it is necessary to pay attention to control and prevent slag inclusion. In fact, these are elementary questions, and there is nothing to say at all.

The titanium added on the basis is similar to the 304L welding process.

The titanium added on the basis of 304L is similar to the welding process of 304L.

Austenitic stainless steel, good weldability, the welding method that can be used depends on the wall thickness, the thickness of the work within 2mm should be argon arc welding, medium and thick plates can be used manual arc welding and submerged arc automatic welding, there will be no knife edge corrosion after welding, and the mechanical properties of the weld metal are 510MPa

1Cr18Ni9Ti is used in the chemical, coal, petroleum industry with high requirements for grain boundary corrosion, heat-resistant parts of building materials and parts with difficult heat treatment, such as:

1 .Petroleum exhaust gas combustion pipelines.

2 .Engine exhaust pipe.

3 .Boiler housings, heat exchangers, furnace components.

4 .Silencing parts for diesel engines.

5 .Boiler pressure vessels.

6 .Chemical transport trucks.

7 .Expansion joints.

8 .Spiral welded pipes for furnace pipes and dryers.

Chemical Composition Carbon C : Silicon Si: . Manganese mn: . Sulfur s : phosphorus p : chromium cr:. Nickel ni:.

Titanium ti: 5(. Mechanical properties.

Tensile Strength b (MPa): 520

Conditional yield strength (mpa): 205

Elongation δ5 (%40

Cross-sectional shrinkage 50

Hardness : 187HB; ≤90hrb;≤200hv

Heat treatment specifications and metallographic structure.

Heat treatment specifications: 1) Solid solution 920 1150 fast cooling; 2) According to the requirements of the buyer, the stabilization treatment can be carried out, and the heat treatment temperature is 850 930, but it must be specified in the contract. 3) The solution temperature should not exceed 1066, and if it does, it must be stabilized to prevent the precipitation of chromium.

Metallographic structure: The structure is characterized by austenite type.

Delivery status: generally delivered in a heat treatment state, and the type of heat treatment is indicated in the contract; If not indicated, it will be delivered in a non-heat-treated state.

l What is the location and color of the crack.

The crack is in the arc crater of arc tightening, generally white or gold, when the arc is filled with arc crater, in the middle of the weld there may be stress (groove gap is too large, the weld meat is too thin) or crystalline crack (that is the problem of the material).

It is best to analyze the specific problem on a case-by-case basis.

A102 seems to be brazed, but I don't remember the grade. If it is brazing. Everyone knows that stainless steel is susceptible to heat deformation and stress.

The brazing metal contains less silver and has poor toughness, so it will crack. Replace with high silver electrodes. If it weren't for brazing, I'd be too talkative.

Crystalline cracks are more likely!

It is also not excluded that the welder has a low level of manual welding!