CN114951919A - Welding method of hastelloy C276 and 316L stainless steel - Google Patents

Abstract

A welding method of hastelloy C276 and 316L stainless steel. In the prior art, crater cracks easily occur, and the welding time is too long, so that the problem that the impact toughness of the weld metal is reduced and the weld metal is embrittled is caused. The invention comprises the following steps: (1) welding materials, wherein an ERNiCrMo-4 welding wire is selected as a welding wire, an ENiCrMo-4 welding wire is selected as a welding rod, the diameter of the welding wire is 1.6mm, assembly is carried out, manual argon tungsten-arc welding is adopted, a mode of filling welding metal with small current more is adopted, and an internal wire feeding welding method is adopted during bottoming; when the interior of the pipeline is filled with argon and is stable, root layer welding is carried out, and the temperature between every two layers is controlled to be no more than 350 ℃; selecting a small welding current, carrying out welding by a rapid welding method, (2) preheating and interlayer temperature, wherein hastelloy welding does not need preheating in a room temperature environment, when the temperature in the air is lower than zero or moisture gathers, heating the base metal at the temperature of 30-40 ℃, (3) carrying out welding current and process parameters, and (4) carrying out welding. The invention relates to a welding method for hastelloy C276 and 316L stainless steel.

Description

Welding method of hastelloy C276 and 316L stainless steel

Technical Field

The invention relates to a welding method of hastelloy C276 and 316L stainless steel.

Background

The weldability of hastelloy C276 is similar to that of austenitic stainless steel in many times, generally, during welding, because the liquid of a molten pool is poor in fluidity, the molten pool is easy to stick and cause incomplete penetration, and the following two problems are mainly encountered in the welding process of hastelloy in the prior art:

(1) the method comprises the following steps of performing intergranular corrosion on a welding joint in a strong corrosion environment, wherein the intergranular corrosion comprises the intergranular corrosion of a welding seam, the 'knife corrosion' of a superheat area close to a fusion line, the intergranular corrosion of a heat affected area at a sensitization temperature and the like; the hastelloy has certain hot crack sensitivity, so that the possibility of generating hot cracks on a welding seam exists, and particularly crater cracks are easy to occur at a final welding point;

(2) in the welding process, a Fe and Cr metal compound, namely an alpha phase, can be formed at the high temperature of 375-875 ℃ for too long time, and the alpha phase has extremely hard and brittle performance and is distributed at a grain boundary, so that the impact toughness of the weld metal is reduced and the weld metal is embrittled;

weldability of hastelloy, 316L stainless steel was analyzed:

1. in the alloy, impurities such as 0, S, P and the like can form low-melting-point eutectic with Ni, and the eutectic is enriched in grain boundaries, so that thermal cracks, particularly microcracks, are easily generated under the action of welding stress;

2. h2, O2, N2, CO and steam blowholes are easily generated during the welding of Hastelloy. H2, O2 and CO are contained in liquid nickel, wherein hastelloy is a nickel-based material, the melting degree is quite large, the melting degree in solid nickel is greatly reduced, and due to poor fluidity of nickel, gas cannot escape in time before weld metal is solidified to form air holes;

3. the Hastelloy has poor thermal conductivity, is easy to overheat, causes coarse grains and greatly reduces the performance of the joint;

4. the unreasonable joint design, the misalignment and the poor assembly can cause larger welding stress, so that cracks are generated;

5. the 316L austenitic stainless steel has low thermal conductivity, large linear expansion coefficient and no magnetism; the tensile strength is larger than or equal to 550N/m2, the yield strength is larger than or equal to 480N/m2, and due to the characteristics of the 316L austenitic stainless steel, large welding internal stress can be generated in a joint after welding, and meanwhile, the interval of liquid-phase lines and solid-phase lines of the 316L austenitic stainless steel is large, the crystallization time is long, and the dendrite directionality of austenite crystals is strong, so that the impurity segregation phenomenon is serious; in summary, the 316L austenitic stainless steel is relatively easy to generate welding hot cracks during welding, including longitudinal and transverse cracks of welding seams, crater cracks, root cracks of backing welding, interlayer cracks of multilayer welding and the like.

Disclosure of Invention

The invention aims to provide a welding method of hastelloy C276 and 316L stainless steel, which adopts a mode of filling welding metal with small current, solves the problems of crater cracks, toughness reduction and embrittlement, and effectively ensures the welding quality of the root part of the welded dissimilar steel.

The above purpose is realized by the following technical scheme:

a welding method of hastelloy C276 and 316L stainless steel comprises the following steps:

(1) welding materials: the welding wire is an ERNiCrMo-4 welding wire, the welding rod is an ENiCrMo-4 welding rod, the diameter of the welding wire is 1.6mm, the welding is performed in an assembly mode, the welding is performed in a free state assembly mode, manual tungsten electrode argon arc welding is adopted, a mode of filling welding metal with small current is adopted, and an internal wire feeding welding method is adopted during bottoming; when the interior of the pipeline is filled with argon and is stable, root layer welding is carried out, and the temperature between every two layers is controlled to be no more than 350 ℃;

(2) preheating and interlayer temperature:

the hastelloy welding does not need preheating in a room temperature environment, when the temperature in the air is lower than zero or moisture is gathered, the base material is heated, the heating temperature is 30-40 ℃, when multilayer welding is adopted, the interlayer temperature is required to be lower than 80-90 ℃, and the interlayer temperature is controlled by a water cooling method;

(3) welding current and process parameters

Selecting a small welding current of 65-95A, and welding by a rapid welding method, wherein the voltage is controlled to be 12-18V during welding;

(4) a welding step:

cleaning a welding area before welding, wherein the cleaning method adopts mechanical cleaning, namely, an angle grinder is used for polishing the welding area until the metallic luster is exposed, the cleaning width is 80-120mm, and impurities are prevented from entering the welding area;

during manual argon tungsten-arc welding operation, a welding material is not directly immersed into a molten pool, the welding material is positioned in front of a tungsten electrode and is fed while being melted, the end part of the welding material is always under argon protection, a direct current direct method is adopted for welding, the end part of the tungsten electrode is ground to be 25-30 degrees, the head part of the tungsten electrode is ground to be a plane, and the selected tungsten electrode is a cerium tungsten electrode;

after each welding pass is finished, removing slag on the surface of the welding pass and eliminating various surface defects, filling a crater when arc is closed in welding to prevent crater cracks, welding a small section of 3-6mm back to each section of welding joint, then advancing along the welding direction, grinding the crater defects by using a grinding wheel, and grinding and flattening the crater;

argon is filled on the back, when the bottom layer is welded by TIG, argon filling protection is uniformly adopted, and the flow of argon is 8-12L/M.

Has the advantages that:

1. the invention relates to a welding process of hastelloy C276 and 316L stainless steel, in particular to a tungsten inert gas shielded arc welding method which can be adopted during welding, such as argon tungsten-arc welding, arc welding and other welding methods, and has wide applicable welding range.

The invention adopts a mode of filling more welding metal with small current, and eliminates and prevents crystal cracking, particularly the problem of crystal cracking of the first layer at the welding root.

When the manual argon tungsten-arc welding operation is adopted, the welding material is not directly immersed into a molten pool, the welding material is positioned in front of a tungsten electrode and is fed while being melted, and the end part of the welding material is always under the protection of argon gas, so that the welding quality is ensured, and the problem of root stress cracking after dissimilar steel welding is effectively solved.

The invention has the advantages of low cost, high welding efficiency, stable process and good reliability, can reduce linear energy, control the fusion ratio of a welding seam, can obtain a qualified welding joint, and can meet the requirements of operation conditions of high-temperature strength and high-temperature corrosion environment on the performance of the welding seam.

Description of the drawings:

FIG. 1 is a schematic view of a weld structure of the present invention.

The specific implementation mode is as follows:

example 1:

a welding method of hastelloy C276 and 316L stainless steel comprises the following steps: (1) welding materials: the welding wire is an ERNiCrMo-4 welding wire, the welding rod is an ENiCrMo-4 welding rod, the diameter of the welding wire is 1.6mm, the welding is performed in an assembly mode, the welding is performed in a free state assembly mode, manual tungsten electrode argon arc welding is adopted, a mode of filling welding metal with small current is adopted, and an internal wire feeding welding method is adopted during bottoming; when the interior of the pipeline is filled with argon and is stable, root layer welding is carried out, and the temperature between every two layers is controlled to be no more than 350 ℃;

(2) preheating and interlayer temperature:

the hastelloy welding does not need preheating in a room temperature environment, when the temperature in the air is lower than zero or moisture is gathered, the base material is heated, the heating temperature is 30-40 ℃, when multilayer welding is adopted, the interlayer temperature is required to be lower than 80-90 ℃, and the interlayer temperature is controlled by a water cooling method;

(3) welding current and process parameters

Selecting a small welding current of 65-95A, and welding by a rapid welding method, wherein the voltage is controlled to be 12-18V during welding;

(4) a welding step:

cleaning a welding area before welding, wherein the cleaning method adopts mechanical cleaning, namely, an angle grinder is used for polishing the welding area until the metallic luster is exposed, the cleaning width is 80-120mm, and impurities are prevented from entering the welding area;

during manual argon tungsten-arc welding operation, a welding material is not directly immersed into a molten pool, the welding material is positioned in front of a tungsten electrode and is fed while being melted, the end part of the welding material is always under argon protection, a direct current direct method is adopted for welding, the end part of the tungsten electrode is ground to be 25-30 degrees, the head part of the tungsten electrode is ground to be a plane, and the selected tungsten electrode is a cerium tungsten electrode;

after each welding pass is finished, removing slag on the surface of the welding pass and eliminating various surface defects, filling a crater when arc is closed in welding to prevent crater cracks, welding a small section of 3-6mm back to each section of welding joint, then advancing along the welding direction, grinding the crater defects by using a grinding wheel, and grinding and flattening the crater;

and argon is filled on the back, when the bottom layer is welded by TIG, argon filling protection is uniformly adopted, and the flow of the argon is 8-12L/M.

Stainless steel has good welding performance, and a 316Cb stainless steel filler rod or a welding rod, 316L stainless steel or 309Cb stainless steel filler rod or welding rod can be adopted for welding according to application.

The structural components of the hastelloy C276 and the 316L stainless steel are as follows:

table 1 chemical composition of the materials:

the welding material has excellent corrosion resistance and technological performance, the diameter of the welding wire is 1.6mm, the chemical components of the welding wire are similar to those of a base metal, the manganese content of the welding wire is higher than that of the base metal, the crack resistance and the pore control can be improved during welding, and meanwhile, the ultra-low carbon content prevents intergranular corrosion danger;

the selection of the welding method is based on the selection of the existing welding equipment, the welding method can be generally performed by manual argon tungsten-arc welding, the welding adaptability is good, a direct-current forward method is selected for welding during welding, when direct-current forward welding is performed, the temperature of a tungsten electrode is low, the allowable current is large, the loss of the tungsten electrode is small, the end part of the tungsten electrode is ground to 30 degrees, the head part is slightly ground to be a plane, the selected tungsten electrode is a cerium tungsten electrode, dirt and oxides are adhered to the surface of hastelloy, so that a welding area needs to be cleaned before welding, the cleaning method can adopt mechanical cleaning, namely, an angle grinder is used for grinding the welding area until the metal luster is exposed, and the cleaning width is more than 100mm so as to ensure that impurities do not enter the welding area;

the hastelloy welding does not need to be preheated generally in a room temperature environment, the base metal is heated only when the temperature in the air is lower than zero or moisture is gathered, but the heating temperature only needs to reach 30-40 ℃, and when multilayer welding is adopted, the interlayer temperature needs to be lower than 80-90 ℃, so that the problem that sigma phase embrittlement is caused due to overlong time at the temperature of 375-875 ℃ is solved;

welding current and other technological parameters, wherein the welding is performed by a quick welding method by selecting small welding current as much as possible in order to reduce welding heat input, but the hastelloy is sticky during welding and is not easy to be welded through, so that the welding current cannot be too small, and the proper heat input speed is adopted during welding to prevent the generation of hot cracks;

specific welding specifications are given in the following table:

table 2 horizontal fixed welding process parameters:

table 3 vertical fixation welding process parameters:

and during specific welding:

(1) small line energy welding is adopted, the stability of arc voltage is kept as much as possible, and an operation method of short arc, no swing or small swing is adopted;

(2) when multilayer welding is carried out, the following regulations are met:

A. after the bottom welding bead is finished, checking the surface of the welding bead by using a magnifying lens, and then checking by using a penetration method;

B. the interlayer temperature is controlled below 60 ℃, and a water cooling method can be adopted to control the interlayer temperature, (a and b are two measures which are mainly taken aiming at preventing welding overheating);

C. after each welding pass is finished, slag on the surface of the welding pass is thoroughly removed, and various surface defects are eliminated;

D. and (3) arc pit treatment: the quality of an arc striking position and an arc withdrawing position is ensured in welding, the arc pit is filled during arc withdrawing to prevent the arc pit from cracking, a small section of weld joint of each section is required to return, then the section advances along the welding direction, the defect of the arc pit is removed by using a grinding wheel, and the arc pit is polished and leveled;

E. after welding, cleaning slag on the surface of a welding seam, surrounding splashes and anti-splashing coating in time;

F. argon is filled on the back, when the bottom layer is welded by TIG, argon filling protection is uniformly adopted, and the flow of the argon is 8-12L/M;

the nickel-based alloy welding wire has the good performances of resisting active gas, caustic medium and reducing acid medium corrosion, has high strength and good plasticity, can be subjected to cold and hot deformation and processing forming and can be welded, and the increase of the nickel content is the most effective means for inhibiting the carbon diffusion in a fusion zone; the welding of the austenitic steel and the austenitic steel can adjust the composition and the structure of a welding seam in a quite wide range by selecting the composition of a filling metal material and controlling the fusion ratio by means of a Schffler tissue diagram; the welded joint treated by the process of the invention is qualified in appearance inspection, ray and ultrasonic flaw detection results, and the normal-temperature mechanical properties and metallographic structure of the welded joint at the two positions are shown in the table 4:

table 4 mechanical properties at room temperature and metallographic structure of the butt joints of C276 and 316L stainless steels:

the scheme of the application has the advantages of low cost, high welding efficiency, good process stability, good reliability and the like, can reduce linear energy, control the fusion ratio of a welding seam, obtain a qualified welding joint, and meet the operation condition requirements of high-temperature strength and high-temperature corrosion environment;

wherein the symbols in figure 1 represent: delta, tube thickness 5mm, alpha, bevel 300-35 deg., root, blunt edge 1.5-2.0mm, b, butt gap 2.0-3.0 mm.

Claims (1)

1. A welding method of hastelloy C276 and 316L stainless steel is characterized in that: the method comprises the following steps:

(1) welding materials: the welding wire is ERNiCrMo-4 welding wire, the welding rod is ENiCrMo-4 welding wire, the diameter of the welding wire is 1.6mm, the welding wire is paired in a free state, manual tungsten electrode argon arc welding is adopted, a mode of filling welding metal with small current more is adopted, and an internal wire feeding welding method is adopted during bottoming; when the interior of the pipeline is filled with argon and is stable, root layer welding is carried out, and the temperature between every two layers is controlled to be no more than 350 ℃;

(2) preheating and interlayer temperature:

the hastelloy welding does not need preheating in a room temperature environment, when the temperature in the air is lower than zero or moisture is gathered, the base material is heated, the heating temperature is 30-40 ℃, when multilayer welding is adopted, the interlayer temperature is required to be lower than 80-90 ℃, and the interlayer temperature is controlled by a water cooling method;

(3) welding current and process parameters

Selecting small welding current of 65-95A, and welding by rapid welding method with voltage controlled at 12-18V

(4) A welding step:

cleaning a welding area before welding, wherein the cleaning method adopts mechanical cleaning, namely, an angle grinder is used for polishing the welding area until the metallic luster is exposed, the cleaning width is 80-120mm, and impurities are prevented from entering the welding area;

during manual argon tungsten-arc welding operation, a welding material is not directly immersed into a molten pool, the welding material is positioned in front of a tungsten electrode and is fed while being melted, the end part of the welding material is always under argon protection, a direct current direct method is adopted for welding, the end part of the tungsten electrode is ground to be 25-30 degrees, the head part of the tungsten electrode is ground to be a plane, and the selected tungsten electrode is a cerium tungsten electrode;

after each welding pass is finished, removing slag on the surface of the welding pass and eliminating various surface defects, filling a crater when arc is closed in welding to prevent crater cracks, welding a small section of 3-6mm back to each section of welding joint, then advancing along the welding direction, grinding the crater defects by using a grinding wheel, and grinding and flattening the crater;

and argon is filled on the back, when the bottom layer is welded by TIG, argon filling protection is uniformly adopted, and the flow of the argon is 8-12L/M.

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