Shanghai Duomu Industry: About the stainless steel welding process

　　Shanghai Duomu Industry has been focusing on stainless steel welding process and has been pursuing innovation in technology. What are the specific points in stainless steel welding? Duomu Industry will share with you about stainless steel welding process here. We will analyze from four perspectives in total:

 

　　A general requirement:

 

　　1. Welders and other related personnel engaged in stainless steel construction should abide by this process.

 

　　2. Tack welding and normal welding must be welded by welders with corresponding grade stainless steel welder certificates.

 

　　Preparation before welding:

 

　　1. Storage, hoisting and transportation

 

　　1.1 Storage of stainless steel parts: There should be special storage racks, which should be wooden or painted carbon steel brackets or cushions with rubber pads to isolate them from carbon steel and other metal materials. When storing, the storage location should be convenient for hoisting, relatively isolated from other material storage areas, and protective measures should be taken. The stainless steel pipes should be covered with protective covers at both ends to prevent dust, oil, and rust from polluting the stainless steel. 1.2 Hoisting of stainless steel parts: When hoisting, special hoisting tools, such as hoisting belts, special chucks, etc., should be used. Wire ropes are strictly prohibited to avoid scratching the surface; and when hoisting and placing, avoid impacts and bumps caused by scratches. 1.3 Transportation of stainless steel parts: during transportation, transportation tools (such as trolleys, tractors, etc.) should be used, and isolation and protection measures should be taken to prevent dust, oil, and rust from polluting the stainless steel. Procrastination is strictly prohibited to avoid bumps and scratches.

 

　　2. The surface of the damaged steel plate needs to be pickled and passivated.

 

　　3. Welding process:

 

　　1. For welding specifications, see "Welding Procedure" (YTRS643-91-01A). Except for the following special requirements, other welding requirements shall be implemented in accordance with "Welding Technical Requirements" (YTRS643-91-02).

 

　　2. Protect the metal surface. It is strictly forbidden to ignite the arc anywhere, and hit the metal surface with a hammer at will.

 

　　3. Temporary components welded with stainless steel (such as horse board, lifting lugs, etc.) should use the same stainless steel material and adopt the corresponding welding process.
 

　　4. When welding stainless steel pipes, inert gas should be passed through the pipe for purification, and the area near the weld must be continuously protected by argon during welding.

 

　　5. When welding stainless steel pipes, TIG welding is required for bottoming.

 

　　6. Use stainless steel grinding wheels and wire brushes for grinding and cleaning.

 

　4. Post-welding treatment:

 

　　1. After welding, the weld seam and near seam area should be pickled and passivated.

 

　　2. The steps of pickling and passivation are as follows:.

 

　　2.1 Clean the surface of the weld.

 

　　2.2 Then apply the pickling and passivation paste to the weld and near the seam area where there is oxide skin, the thickness of the coating film is 1~3mm.

 

　　2.3 The reaction is generally 1-10 minutes, below 0℃, when the oxide scale needs to be extended appropriately (the reaction time depends on the paste brand and the thickness of the metal oxide film).

 

　　2.4 After the reaction is complete, wipe it off with a rag or silk brush, and rinse with clean water.

 

　 Scope

 

　　This process standard is applicable to manual arc welding of steel structure production and installation in general industrial and civil construction projects.

 

　　Construction preparation

 

　　2.1 Materials and main machinery:

 

　　2.1.1 Welding rod: its model is selected according to the design requirements and must have a quality certificate. Bake before welding as required. It is strictly forbidden to use electrodes with peeling coatings and rusty cores. When there is no design regulation, E43 series carbon steel structure electrode should be used when welding Q235 steel; E50 series low alloy structural steel electrode should be used when welding 16Mn steel; low hydrogen electrode (basic electrode) should be used when welding important structures. After baking according to the instructions, put it in a heat preservation bucket and take it as needed. Acid electrodes and alkaline electrodes are not allowed to be mixed.

 

　　2.1.2 Arc pilot plate: arc plate is required when connecting with groove, and the material and groove type of the arc plate should be the same as that of the weldment.

 

　　2.1.3 Main machines and tools: electric welding machine (AC, DC), welding handle, welding tongs, mask, small hammer, welding rod oven, welding rod insulation barrel, steel wire brush, asbestos cloth, thermometer, etc.
 

　　2.2 Operating conditions

 

　　2.2.1 Familiar with the drawings, and make technical clarifications about the welding process.

 

　　2.2.2 The validity period of the welder's certificate should be checked before welding, and the welding work that the welder can undertake should be proved.
 

　　2.2.3 The on-site power supply should meet the welding power requirements.

 

　　2.2.4 The ambient temperature is lower than 0℃, the preheating and post-heating temperature should be determined according to the process test.

 

　　Operation process

 

　　3.1 Process flow

 

　　Work preparation→arc welding (flat welding, vertical welding, horizontal welding, overhead welding)→weld seam inspection

 

　　3.2 Arc welding of steel structure:

 

　　3.2.1 Flat welding

 

　　3.2.1.1 Choose the appropriate welding process, electrode diameter, welding current, welding speed, welding arc length, etc., and verify through welding process test.

 

　　3.2.1.2 Cleaning the weld: Before welding, check whether the groove and the assembly gap meet the requirements, whether the positioning welding is firm, and there should be no oil and rust around the weld.

 

　　3.2.1.3 The baking electrode should meet the specified temperature and time. The electrode taken out of the oven should be placed in the electrode insulation barrel and taken as needed.
 

　　3.2.1.4 Welding current: Choose an appropriate welding current according to factors such as weldment thickness, welding level, electrode type, diameter, and welder's proficiency.

 

　　3.2.1.5 Arc ignition: the starting and falling arc point of the fillet weld should be at the end of the weld, preferably greater than 10mm, and should not be arcing casually. The electrode should be pulled away from the weld area immediately after ignition and arcing, so that the electrode and the component Keep a gap of 2～4mm to generate an arc. For butt welds and combined butt and fillet welds, pilot arc plates and lead plates are provided at both ends of the weld. The arc must be ignited on the pilot arc plate before welding to the weld area, and the halfway joint should be in front of the weld joint Start the arc at 15-20mm. After preheating the weldment, return the electrode to the beginning of the weld and fill the molten pool to the required thickness before welding forward.

 

　　3.2.1.6 Welding speed: constant speed welding is required to ensure that the thickness and width of the weld are uniform. The molten iron in the molten pool and the slag are kept at an equal distance (2～3mm) from the inside of the mask.

 

　　3.2.1.7 Welding arc length: It is determined according to different types of electrodes. Generally, the arc length is required to be stable and unchanging. The acid electrode is generally 3~4mm, and the alkaline electrode is generally 2~3mm.

 

　　3.2.1.8 Welding angle: Determined according to the thickness of the two weldments. There are two welding angles. One is the angle between the electrode and the welding advancement direction is 60-75°; the other is the angle between the electrode and the welding left and right. There are two situations. When the thickness of the weldment is equal, the angle between the electrode and the weldment is 45°; when the thickness of the weldment is not equal, the angle between the electrode and the thicker weldment should be greater than the angle between the electrode and the thinner weldment.

 

　　3.2.1.9 Arc closing: After each weld is welded to the end, the arc crater should be filled, and the arc should be carried in the opposite direction of the welding direction, so that the arc crater is thrown inside the weld bead to prevent the arc pit from biting meat. After welding, gas cutting should be used to cut off the arc plate, and it should be ground and smooth, and it is not allowed to use a hammer to knock it down.

 

　　3.2.1.10 Slag removal: After the entire weld is welded, the slag is removed. After the welder's self-inspection (including appearance and weld size, etc.) is correct, the welding can be continued.

 

　　3.2.2 Vertical welding: The basic operation process is the same as that of flat welding, but the following issues should be noted:

 

　　3.2.2.1 Under the same conditions, the welding power source is 10% to 15% smaller than the flat welding current.

 

　　3.2.2.2 Short arc welding is adopted, and the arc length is generally 2 to 3 mm.

 

　　3.2.2.3 The angle of the welding rod is determined according to the thickness of the weldment. The thickness of the two weldments is equal, and the angle between the electrode and the electrode in the left and right directions is 45°; when the thickness of the two weldments is different, the angle between the electrode and the thicker weldment should be greater than the angle on the thinner side. The welding rod should form an angle of 60°～80° with the vertical surface, so that the arc is slightly upward and blows toward the center of the molten pool.

 

　　3.2.2.4 Arc closing: When the welding reaches the end, use the arc discharge method to fill the arc crater, and move the arc to the center of the molten pool to stop the arc. It is strictly forbidden to leave the arc crater aside. In order to prevent meat biting, the arc should be lowered and the angle of the electrode should be changed so that the electrode is perpendicular to the weldment or blown down slightly from the arc.

 

　　3.2.3 Horizontal welding: basically the same as flat welding, the welding current is 10% to 15% lower than that of flat welding under the same conditions, and the arc length is 2 to 4mm. The angle of the welding rod, the welding rod should be inclined downward during horizontal welding, and the angle is 70°～80° to prevent the iron from falling. According to the thickness of the two weldments, the angle of the welding rod can be adjusted appropriately, and the forward direction of the welding rod and welding is 70°～90°。

 

　　3.2.4 Overhead welding: It is basically the same as vertical welding and horizontal welding. The welding rod is related to the angle of the weldment and the thickness of the weldment. The welding rod forms an angle of 70° to 80° with the welding direction. It is suitable to use small current and short arc welding.
 

　　3.3 Winter low temperature welding:

 

　　3.3.1 When arc welding is carried out under the condition of ambient temperature lower than 0℃, in addition to complying with the relevant regulations of normal temperature welding, the welding process parameters should be adjusted to make the weld and the heat-affected zone slowly cool down. Windshield measures should be taken if the wind force exceeds level 4; the uncooled joints after welding should be avoided from contact with ice and snow.

 

　　3.3.2 In order to prevent welding cracks, steel structures should be preheated and preheated to control the temperature between layers. When the temperature of the working place is below 0℃, a process test should be carried out to determine the appropriate preheating and post-heating temperature.

 

　　Quality Standard

 

　　4.1 Guaranteed items
 

　　4.1.1 Welding materials should meet the design requirements and relevant standards, and the quality certificate and baking records should be checked.
 

　　4.1.2 The welder must pass the examination and check the certificate of the welder's corresponding welding conditions and the evaluation date.

 

　　4.1.3 Class I and II welds must be inspected by flaw detection, and shall meet the design requirements, construction and acceptance specifications, and check the weld flaw detection report.

 

　　4.1.4 No cracks, weld bead, burn-through, arc crater and other defects on the surface of welded seam Ⅰ and Ⅱ welds. Class Ⅱ welds must not have defects such as surface pores, slag inclusions, arc craters, cracks, arc scratches, etc., and class Ⅰ welds must not have defects such as undercuts and insufficient welds.
 

　　4.2 Basic items

 

　　4.2.1 Appearance of weld seam: uniform weld seam appearance, smooth transition between weld bead and weld bead, weld bead and base metal, and weld slag and spatter are removed.

 

　　4.2.2 Surface pores: Class Ⅰ and Ⅱ welds are not allowed; for class Ⅲ welds, the allowable diameter of each 50mm length of the weld is ≤0.4t; and there are 2 pores ≤3mm; the spacing of the pores is ≤6 times the diameter.

 

　　4.2.3 Undercut: Class I welds are not allowed.

 

　　Class Ⅱ weld: depth of undercut ≤0.05t, and ≤0.5mm, continuous length ≤100mm, and total length of undercut on both sides ≤10% of weld length.

 

　　Grade III weld: undercut depth ≤0.lt, and ≤lmm.

 

　　Note; t is the thinner plate thickness at the joint.

 

　　4.3 Allowable deviation items

 

　　Welding seam reinforcement b<200.5～20.5～2.50.5～3.5

 

　　1 Butt welding seam (mm) b≥200.5～30.5～3.50～3.5 use <0.1t and <0.1t and <0.1t and welding greater than 2.0, not greater than 2.0, not greater than 3.0, welding angle size hf≤60～+1.5 seam 2 angles Welding seam (mm) hf>60～+3 quantity Welding seam reinforcement hf≤60～+1.5 gauge (mm) hf>60～+3 inspection 3 combined welding seam T-joint, cross joint, angle joint>t/4 Check the size of the welding angle, the lifting weight is ≥50t, the T-joint of the intermediate working crane beam is t/2 and ≯10

 

　　Note: b is the width of the weld, t is the thinner plate thickness at the joint, and hf is the size of the weld angle.

 

　　Finished product protection

　　5.1 Do not hit the joints after welding, and do not water the steel that has just been welded. Slow cooling measures should be taken at low temperatures.

 

　　5.2 It is not allowed to ignite the arc on the base metal outside the weld at will.

 

　　5.3 Welding can only be performed after the various components are calibrated, and the pad irons and fixtures should not be moved at will to prevent the size deviation of the components. The welds of concealed parts must go through the concealed acceptance procedures before proceeding to the next concealed process.

 

　　5.4 Low-temperature welding is not allowed to remove the slag immediately, and it should be done after the welding seam has cooled down.

 

　　Quality issues that should be paid attention to

 

　　6.1 The size exceeds the allowable deviation: For the deviation of the weld length, width, thickness, center line deviation, bending, etc., the relative position and size of the welding part should be strictly controlled, and the welding should be carried out after qualified, and the welding should be carefully operated.

 

　　6.2 Weld cracks: In order to prevent cracks, suitable welding process parameters and welding procedures should be selected, high current should be avoided, and the flame should not be suddenly extinguished. Weld joints should be spanned by 10 to 15mm. Welding wood allows moving and knocking. Pieces.
 

　　6.3 Surface pores: The welding rod is baked according to the specified temperature and time. The welding area must be cleaned. During the welding process, select an appropriate welding current, reduce the welding speed, and make the gas in the molten pool completely escape.
 

　    6.4 Welding slag: multi-layer welding should remove the welding slag layer by layer, the operation should be correct and the arc length should be appropriate. Pay attention to the flow direction of the slag. When using alkaline electrodes, the slag must be left behind the slag.

 

　　Quality Records

 

　　This process standard shall have the following quality records:

 

　　7.1 Quality certificate of welding materials.

 

　　7.2 Welder certificate and number.

 

　　7.3 Welding process

 

　　7.4 Welding quality inspection report and flaw detection report.

 

　　7.5 Design changes and negotiation records.

 

　　7.6 Acceptance records of concealed works.

 

　　7.7 Other technical documents.

 

　　A set of technological procedures and technical regulations in the welding process, including technical regulations on welding methods, pre-welding preparations, assembly, welding materials, welding equipment, welding sequence, welding operations, welding process parameters, and post-welding treatments. In welding production, the analysis of the welding process, the formulation of the welding process, and the realization of the welding process are to ensure welding......

 

　　Shanghai Duomu Industrial Co., Ltd. is a high-tech industry specializing in power supply development. Welding power supply is my key project. The series of welding machines developed have reached or exceeded the international advanced level, and are well recognized by customers and have a wide customer base. And popularity. The products are professionally used for welding precision parts and thin plates, surfacing welding of valves, rolls, picks, etc., welding repair of molds, mechanical shafts, etc., and have been widely used in electronic appliances, coal mining machinery, aerospace and many other fields.

　　

Surfacing machine	Plasma powder surfacing machine	Multifunctional plasma surfacing machine	Multifunctional plasma powder surfacing machine	High-power plasma surfacing machine
	Integrated multifunctional plasma powder surfacing machine	Micro beam plasma surfacing machine	Multifunctional precision surfacing machine
Valve surfacing	Valve surfacing equipment
Powder surfacing gun	100A handheld powder surfacing gun	150A plasma welding gun	300A plasma welding gun	Plasma welding gun for 500A machine
	100A handheld powder surfacing gun	160A machine type powder surfacing gun	300A machine type powder surfacing gun	Plasma surfacing welding machine 160A
other	Plasma wear-resistant sheet	Thin plate welding	Abrasive repair
	Screw surfacing	Middle groove surfacing	Metal surface strengthening

　Service Process:

 

　　1. Sample test (the customer provides sample test to let the customer know the equipment's surfacing effect and whether it can meet the customer's requirements, so that the customer can be more assured)

 

　2. Signing the contract (the contract is delivered by courier or fax)

 

　3. On-site delivery (to the customer’s company for equipment installation, commissioning and training)