Steel structure welding knowledge

The steel structure refers to the structure of the steel material, which is one of the main building structural types. The structure is mainly composed of steel beams, steel columns, steel truss, etc. made of steel and steel plate, etc., and weld, bolts or rivets are typically employed between components or components. Because of its high weight, it is easy to construct, widely used in large factory buildings, venues, super high-level. The steel structure is in the welding process, there are many things that need attention, once negligence, it is possible to cast into a big mistake. The following is the knowledge point of all steel structures sold by Guangxi Hongyu Steel Structure, and friends who need it can watch the collection!

I. Steel structure welding process standard

(1) range

This process standard applies to steel structural production and installation of manual arc welding welding projects in general industrial and civil construction projects.

(2) Construction preparation

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2.1 Materials and Majors

2.1.1 Welding: The model is selected according to the design requirements, and must have a quality certificate. After being welded as required. It is strictly forbidden to use the carnotene, the solder core rust. When design is not specified, the welding Q235 steel should be used for E43 series carbon steel structural electrode; welding 16MN steel should be used for E50 series low alloy structural steel electrodes; welding important structures should be used to use low hydrogen type electrodes (alkaline electrodes). After baking according to the requirements of the specification, place it in the thermal insulation barrel and take it. The acidic electrode is not allowed to be mixed with alkaline electrodes.

2.1.2 Rejecting Arc: Use the curved plate with a groove, and the arc sheet and the grooved shape should be the same as the solder.

2.1.3 Main machines: electric welding machine (intersection, DC), welding line, welding tongs, mask, small hammer, electrode oven, welding rod insulation barrel, wire brush, stone cotton strip, temperature meter, etc.

2.2 Working conditions

2.2.1 Familiar with drawings, doing welding process technology.

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2.2.2 Before the welder should be checked before the welder shall be checked, and the welding work that the welder can be proved.

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2.2.3 On-site power supply shall comply with the welding requirements.

2.2.4 The ambient temperature is below 0 ° C, and the thermal temperature should be determined according to the process test.

(3) Operation process

3.1 Process:

Work preparation → arc welding (soldering, welding, welding, ledd weld) → Welding examination

3.2 Steel structure arc welding:

3.2.1 flat welding

3.2.1.1 Select the qualified welding process, welding rod diameter, welding current, welding speed, welding arc length, etc., by welding process test verification.

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3.2.1.2 Clean up the welding: Water inspection slope mouth, whether the assembly clearance meets the requirements, whether the positioning weld is firm, no oil, rust around the weld.

3.2.1.3 Baking welding rod shall comply with the specified temperature and time, from the electrode removed from the oven, placed in the welding rod insulation barrel, followed.

3.2.1.4 Welding current: According to the thickness of the weldment, the welding level, the welding rod model, the degree of welder, the degree of welder, etc., selects a suitable welding current.

3.2.1.5 Arc: The angular weld should be in the end of the weld, which should be more than 10mm, should not arc arcing, and immediately pull the electrode from the weld area, so that the welding rod and member Keep an arc in 2 to 4 mm gap. The docking weld is connected to the corner and the angle joint weld, and the arcing plate and the lead plate are provided on both ends of the weld. After the arcing arcing on the arcing plate, then the weld area is then soldered, and the secondary joint should be in front of the weld joint. 15 ~ 20mm fire arc, the welding is preheated, and then the welding rod will be retracted to the starting placement, fill the molten pool to the required thickness, and weld before.

3.2.1.6 Welding speed: require equal speed welding, ensure the thickness of the weld, uniform width, from the mask, the molten tank is maintained in the molten tank (2 to 3 mm).

3.2.1.7 Welding Arc Length: Determined according to the electrode model, generally required that the arc length is stable, and the acid electrode is generally 3 to 4 mm, and the alkaline electrode is generally 2 to 3 mm.

3.2.1.8 Welding angle: According to the thickness of the two solders, there are two aspects, one is that the angle between the welding rods and the welding direction is 60 to 75 °; the second is two cases of the welding rod and the welding left and right angles, When the thickness of the welding is equal, the welding rod and the welding angle are 45 °; when the thickness of the weldment is not equal, the side angle of the electrodes and the thick welds should be greater than the side angle of the welding rod and the thinner weldment.

3.2.1.9 Arc: Each weld is welded to the end, and after the arc is filled, the direction of the welding direction is arc, so that the arc pits are in the soldering path to prevent arc pits. After the welding is completed, the gas cuts should be used to remove the arc plate, and we will be worn and flat, and the hammer is not allowed.

3.2.1.10 Clearance: After the whole weld is welded, the slag is removed. After the welder self-test (including appearance and weld size, etc.) is not problematic, and the transfer site will continue to be welded.

3.2.2 Spotting: Basic Operation Process The process is the same as soldering, but should pay attention to the following problems:

3.2.2.1 Under the same conditions, the welding power supply is 10% to 15% lower than the soldering current.

3.2.2.2 Using short arc welding, 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 to 45 ° in the left-right direction of the electrode and the electrode; when the thickness of the two weldments is not equal, the angle between the electrodes and the thickened welds should be larger than the angle of the thin side. The electrode should be formed from a vertical surface to the vertical surface, and the angular arc is slightly upward, blowing to the center of the molten pool.

3.2.2.4 Arc: When welded to the end, the arc is filled with the arc method, and the arc is moved to the central arc of the molten pool. It is strictly forbidden to make the arc pit. In order to prevent biting, it should be lowered by the arc conversion electrode, so that the electrodes are vertical or blown downward by the arc.

3.2.3 Priority: Basically, the same welding current is 10% ~ 15% lower than the current of the same condition, and the arc length is 2 to 4 mm. At the angle of the welding rod, the welding rod should be tilted downward, and the angle is 70 ° ~ 80 °, preventing iron water from falling down. According to the thickness of the two solders, the electrode angle can be adjusted, and the welding rod and the welding direction of 70 ° ~ 90 ° may be adjusted.

3.2.4 Yangwear: Basically, the same as the welding, the solder, and the welding rods are related to the thickness of the weldment, the welding rods are 70 ° to 80 ° in the welding direction, which should be used with small current, short arc welding.

3.3 Winter low temperature welding:

3.3.1 When performing arc welding at ambient temperature below 0 ° C, in addition to complying with the relevant regulations of the normal temperature welding, the welding process parameters should be adjusted to slow cooling the weld and heat affected zone. The wind is more than 4, and the windshield method should be taken; the joint that is not cooled after welding should avoid encountering the ice.

3.3.2 Steel structure to prevent welding cracks, should be preheated, preheated to control the interlayer temperature. When the working place temperature is below 0 ° C, the process test should be performed to determine the appropriate preheating, and then heat temperature.

(4) Quality standard

4.1 Guarantee Project

4.1.1 Welding materials shall comply with the design requirements and relevant standards, and should check the quality certificate and baking records.

4.1.2 Welder must pass the examination, check the certificate of the welder corresponding welding conditions and the date of assessment.

4.1.3 I, and II welds must be inspected by the impairment and should comply with the design requirements and construction and acceptance norms, and inspect the weld reflection report.

4.1.4 Weld Surface I, II welds shall not have cracks, solder tumors, burning, and curved brakes. Level II welds must not have surface air holes, slag, arc, cracks, arc scratches, etc.

4.2 Basic Projects

4.2.1 Solder appearance: Uniform weld shape, welding tract and soldering tract, soldering and splash between the soldering and the basic metals are cleaned.

4.2.2 Surface air hole: I, II welds are not allowed; the III weld is allowed to be ≤0.4t in length per 50 mm; and 2 ≤ 3mm air holes; the pores pitch ≤ 6 times aperture.

4.2.3 Bite: The level I weld is not allowed.

Level II weld: The depth of the bite is ≤0.05T, and is ≤0.5mm, the continuous length is ≤100mm, and the length of the bite of both sides is ≤10% weld length.

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Level III weld: The depth of the bite is ≤0.1T, and ≤ 1 mm.

Note: T is a thinning plate thickness.

4.3 Allow Deviation Projects

See the table.

(5) Finished product protection

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5.1 When the welding is not allowed to hit the joint, it is not allowed to water on a steel steel. Clever measures should be taken at low temperatures.

5.2 Not allowed to arc on the solder in the solder.

5.3 All kinds of components can be soldered, and the horn and cartridges are not allowed to prevent the component size deviation. The welds in the hidden part must be procedures for hidden acceptance procedures.

5.4 Low-temperature welding is not allowed to immediately clear the slag, and should be carried out after cooling.

(6) Quality issues that should be paid attention to

6.1 Size beyond the allowable deviation: the length of the weld, the width, thickness, the center line offset, the bending, etc.

6.2 Weld Crack: To prevent crack production, choose suitable welding process parameters and soldering procedures to avoid large currents, do not suddenly turn off, the weld joint should be connected to 10 ~ 15mm, welding is not allowed to move, tap Weldment.

6.3 Surface air hole: The electrode is baking according to the specified temperature and time, and the welding area must be cleaned and the appropriate welding current is selected during the welding process, reducing the welding speed, so that the gas in the molten pool is completely essential.

6.4 Welded Scrap: Multi-layer welding should be cleaned clean, and the operation should be carried out correctly, and the arc length is appropriate. Pay attention to the flow direction of the slag, when using the alkaline electrode, the slag must remain behind the slag.

(7) Quality record

This process should have the following quality records:

7.1 Welding Material Quality Certificate.

7.2 Welder certificate and number.

7.3 Welding process test report.

7.4 Welding quality inspection report, reflection report.

7.5 Design changes, negotiate records.

7.6 Connecting Project Acceptance Record.

7.7 Other technical documents.

Second, steel structure welding prohibition and pressing method

When welding, do not pay attention from the welding order, personnel arrangement, slope form, welding specification, etc., resulting in large deformation, correction, increased cost, especially thick plates and large workpieces, and large workpieces. Crack or layered tear. Now let’s take a look at the welding taboo and suppression method of steel structure:

(1) Welding does not pay attention to control welding deformation

[Harmful phenomenon]

When welding, do not pay attention from the welding order, personnel arrangement, slope form, welding specification, etc., resulting in large deformation, correction, increased cost, especially thick plates and large workpieces, and large workpieces. Crack or layered tear. Correcting high costs with flames and is not easy to cause heat. Workpieces with high precision requirements, do not take effectively control deformation measures, installation size does not meet the requirements, and even cause rework or scrap.

[Prevention and Treatment Method]

In the reasonable welding sequence and use appropriate welding specifications and methods of operation, reverse deformation and rigid fixing measures are used.

(2) Welding in the joint gap in the welding strip head or iron block

Since the welding is difficult to integrate the welding strip or iron block with the solder, it can cause welding defects that are not fused, unmeted, and reduce the connection strength. If filling with rusty welding bales or iron blocks, it is difficult to ensure that the material is consistent with the material of the base material; These situations will greatly reduce the quality of the welds of the joints, and do not meet the quality requirements for the design and standardization of weld.

1) When the workpiece assembly gap is large, it is not exceeded that the range is allowed, and the assembly gap exceeds the thin plate thickness of 2 times or greater than 20 mm, the depositor is applied to fill the recessed portion or decrease the assembly gap. It is strictly forbidden to use a method of filling welding strips or iron blocks in the joint gap.

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2) When the part is processed, it should be noted that the cutting margin and the cutting of welding receded shrinkage are restored, control the size of the parts, do not increase the gap to ensure the dimensions.

(3) When using different thicknesses and widths, it is not gentle transition.

When docking with different thicknesses and widths, the thickness difference of the board is not paid within the standard permission range, such as not in the allowable range and does not make a gentle transition process, such weld seams are easily stressed in the thickness of the thin plate thickness. Produce welding defects such as unfused, affecting the quality of welding.

When the relevant regulations should be welded into a slope shape, the maximum allowable value of the slope should be 1: 2.5; or the thickness is machined into a slope before welding, and the maximum allowable value of the slope is 1: 2.5, when directly The structure slope slope that is subjected to a moving load and needs to perform fatigue verification should not be greater than 1: 4. When the sheets of different widths, the method of thermal cutting, machining or grinding wheel should be used in accordance with the factories and construction conditions, and the maximum allowable slope value is 1: 2.5.

(4) Do not pay attention to welding sequence on the components with cross welds

For components with cross welds, do not pay attention to the reasonable arrangement of welding sequence by analyzing the impact of welding stress release and welding stress on components, but as assessed and randomly welded, resulting in a longitudinal seam to constrain each other, resulting in large temperature shrinkage Stress, deformation of the board, the panel surface is uneven, and it is possible to make the weld cracks.

For components with cross welds, a reasonable soldering order should be developed. When several vertical and horizontal cross weld weld weld, the transverse seams are largely deformed, while the rear welded welds are welded, so that when welding lateral welds, they will not be bound by longitudinal welds, so that the seam shrinkage stress In the case of unconstrained, the welding deformation can be reduced to ensure the quality of the weld, or the weld weld is welded before the weld is welded.

(5) The lap joint of the type steel stem is served in the corner, and weld welding at the angle.

When the steel stem member is welded with the continuous sheet lap joint, the weld is welded on both sides of the first welded part, and weld the soldering end weld, no welding. Thus, although it is advantageous to reduce the welding deformation, stress concentration and welding defects are easily generated in the corner of the rod, affecting the quality of the welded joint.

[Harmful phenomenon]

[Harmful phenomenon]

[Harmful phenomenon]

[Harmful phenomenon]

[Prevention and Treatment Method]

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[Prevention and Treatment Method]

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[Prevention and Treatment Method]

[Prevention and Treatment Method]

When the strip side of the steel stem is welded, the welding should be completed at the angle. Do not welder to the corner and run to the other side to weld.

(6) Requirement, etc.

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[Harmful phenomenon]

When the welding docking weld, a full melting angle-in-plane weld, the weld of the crane beam flange plate and the web, does not add an arc on the arc and the leading plate at the arcing and the lead, so that during the welding end, due to the current voltage Not stable enough, the temperature of the stop point is not stable enough, and it is easy to cause the end of the end weld, unfelt, unmete, crack, scrap, porront, and the strength of the weld, can not meet the design requirements.

In the welding docking weld, the full fused angle weld and the weld of the crane beam flaps and the web should be provided on both ends of the weld, and the action is part of the defects to defects both ends. After introducing the workpiece, then cut the defective portion to ensure the quality of the weld.

(7) Do not pay attention to welding speed and welding current, coordination of electrode diameter

Do not pay attention to the welding speed and welding current during welding; the welding position is coordinated. If the bottom welding is permeted, due to the narrow root size, such as the welding speed is too fast, the root gas, the slag is not sufficiently discharged, which is easy to produce unmeted, slag, air hole and other defects. When the cover is welded, if the welding speed is too fast, it is also easy to generate a pore; the welding speed is too slow, the welding is too high, the shape is not neat; the welding is too small, the welding speed is too Slow, easy to be burned.

The welding speed has a significant impact on welding quality and welding productivity. When using welding current, weld position (bottom weld, filling welding, cover weld), the thickness of the weld, the slope size is appropriately welded, in ensuring melting Large welding speeds are selected for the premise of gas, gas, welding slag, and not burned, well-formed, to improve productivity.

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(8) The weld joint contact or corner docking combination weld welding angle is not enough.

T-joint, cross joint, corner joint, etc. Requests melt-docking or corner combined weld, its solder foot size is insufficient, or the web or the web of the crane beam or the like of the hinderometer is designed to be connected to the upper wing plate The weld foot is not enough, which will make the strength and stiffness of the welding fail to meet the design requirements.

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T-joint, cross joint, corner joint, etc. Requests melt-docking combination weld, should have sufficient welding foot requirements in accordance with design requirements, and generally not less than 0.25T (T is thinner). Plate thickness). A crane beam or a similar web with a fatigue check requirement is 0.5T to the upper flange, and should not be greater than 10 mm. The allowable deviation of the welding size is 0 to 4 mm.

(Nine) Multi-layer weld does not remove the surface of welding slag and weld surfaces

When the thick plate multilayer welding .

When the thick plate multilayer welding, the soldering should be welded each at each layer. After each layer of weld welds should be removed, the solder slag, weld surface defects and splashes should be removed, and the defects such as slag, air holes, cracks, and cracks that affect welding quality should be thoroughly removed.

(10) Do not pay attention to control arc length when welding

When welding, the arc length is appropriately adjusted according to the form of the groove form, the number of welding layers, welding form, the welding rod model, etc.. Due to improper use of welding arc, it is difficult to get high quality weld.

[Prevention and Treatment Method]]

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In order to ensure the quality of the weld, the short arc operation can be used in the weld, but the appropriate arc length can be selected according to different situations to obtain the optimal welding quality, such as the V-shaped slope, the first layer of the corner should be used. Short arcs to ensure welding, and do not bite phenomenon, the second layer can be slightly longer to fill the weld. When the gap of the weld is small, the arc can be used with a large number of gaps, and the welding speed is accelerated. The oil soldering arc should be shortest to prevent the flow of iron water; vertical soldering, in order to control the temperature of the molten pool, it is necessary to use small current and short arc welding. In addition, no matter what solder, pay attention to always keep the arc length in the event of a substantially constant, and ensure that the melt width of the entire weld is consistent.

(11) Multi-layer welding discontinuous welding does not pay attention to control inter-interlayer temperature

When the thick plate multi-layer welding, do not pay attention to the interlayer temperature control, such as excessive interval intervals, no preheating, welding is easy to create cold cracks between layers; if the interval is too short, the interval temperature is too high 900 ° C), the performance of weld and thermal affected zones will also have an impact, which will cause crystal grains, causing toughness and plasticity, will leave potential hazards on the joint.

When the thick plate multi-layer welding should be strengthened, the temperature of the interlayer temperature should be inspected, and the temperature of the welded base material should be verified during continuous welding, so that the interlayer temperature can be consistent with the preheating temperature, and the highest temperature between the layers is also To be controlled. The welding time should not be too long. When there is a case where the welding is interrupted, the preheating temperature should be appropriately higher than the initial preheating temperature when welding the welding.

(12) Multi-storey weld does not remove the surface of weld and weld surfaces

Third, the correct steel structure welding method

(one)

The large diameter flange is in the welding construction, although there is only one weld, but considers the welding deformation and welding quality, the X-shaped leader is taken.

First, the annular blank is fixed on the gantry clamp platform, and then the groove processing is performed, and the groove processing will be cut by the flame, and then be ground with a grinding wheel, require smooth, flat, no obvious groove. Defects such as the surface of the groove and two sides of iron, impurities, moisture, oil stains and layers.

Since the thickness of the blank is thick, select the appropriate welding method directly affect the degree of deformation generated by the welding. Select hand welding to perform both sides of symmetrical welding.

(two)

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If the large diameter flange is improper, it is still possible to generate welding deformation.

For example, first welding the X-slope mouth, then weld the other side;, when the first side is soldered, the structure rigidity is still small, the welding is large, when the welding is reverse, the front weld has been formed, the structure is rigid Increased, at this time, the amount of deformation caused by soldering is small than the front, although the deformation direction is opposite, but does not completely cancel, and finally retain the deformation direction of the first side.

According to the thickness of the welding workpiece, the number of solder layers is determined, the workpiece is 50mm, and the workpiece is divided into 10 layers. 5 floors per surface, welding is used to be called welding, and the hammering weld is several times after each layer of welding is completed. After the weld is completely cooled, remove the tool fixture and try to eliminate welding stress.

(three)

After the large-diameter flange welding is completed, a comprehensive RT or UT examination is required according to JN4700. Since the welding portion is part of the stress concentration and the flange intensity, non-destructive testing must be carried out, and the level requirements must be reached. UT check must reach the level I pass, or RT must reach the II qualified, and the detection method is performed in accordance with JB4730.

Fourth, steel structure welding national standards and technical procedures

(1) The welding materials such as welding rods, welding wire, flux, electric slag welding tissue and the material should comply with the design requirements and the national standard “Building Steel Structure Welding Technical Regulations” JGJ81. Welding rods, flux, diesel wire, flexion, etc., should be baking and stored according to the provisions of its product specification and welding process documents.

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Note: The welding material has a significant impact on the quality of steel structural welding projects. Its choice must meet the requirements of design documents and national standards. For the welding material of the experience, the product is produced, the production date, the storage state, and the use of baking, etc. also directly affect the quality of welding.

This article specifies the use and use requirements of the electrode, especially emphasizing the baking state, which is the necessary means of ensuring welding quality.

(2) Welder must pass the examination and obtain a certificate of qualification. Welders must be soldered within their test qualified projects and their accreditation.

Note: In the construction welding of steel structure engineering, welders is a special type of work, and the operation skills and qualifications of welders will ensure that the quality of the project must fully pay. The welders referred to in this article include manual operating welders, mechanical operating welders.

Welder engaged in the welding construction of steel structural engineering, according to the specific type of steel structure welding project, according to the national current industry standard “Building Steel Structure Welding Technical Procedures” JGJ81 and other technical procedures, the soldering welder is examined and obtained corresponding certificates .

(3) The construction unit shall perform the welding process to determine the welding process according to the assessment report.

Note: Welding nodes and welded joints in steel structural engineering, it is impossible to perform field physical sampling inspection, and the flaw can only determine the geometric defect of weld, and cannot determine the physical and chemical performance of the joint. In order to ensure the quality of engineering welding, construction welding process specification must be installed in component production and construction.

This article stipulates that the construction enterprises must conduct process assessments, and the construction unit shall conduct a corresponding process assessment according to the type of steel structure undertake, according to the national current industry standard “Building Steel Structure Welding Technical Regulations” JGJ81 and other technical procedures.

(4) The design requires that the general welding of the whole welding should be inspected by ultrasonic flaw detection. When ultrasonic flaw detection cannot be judged to defect, ray flaw detection, the internal defect grading and the impairment method should comply with the current country. Standard requirements.

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Welding ball node grid weld, bolt ball node grid weld and round tube T, K, Y-shaped point joint wire weld, its internal defect grading and impairment method should comply with national current standards. See Table 3.4.5

Note: The standard regulations require 100% inspection of the first-served first-stage weld, and the local inspection of the secondary weld is specified as a sampling test. The steel structure is generally longer, and it is protected by each weld according to the specified percentage, and each of the regulations are not less than 200 mm, which is advantageous for ensuring that each weld quality is advantageous.

However, the steel structure mounting weld is generally not long, and most welds are connected to the beam. The length of each weld is mostly between 250-300mm, and the number of solder strips is sampling is feasible.

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1.5 T-shaped joint, cross joint, corner joint requires a split-free docking and angular docking combination weld, which should not be less than t / 4; the web is designed with a crane beam or the like of the like. The solder foot of the upper wing wondered weld is T / 2 and should not be less than 10 mm. The allowable deviation of the solder foot size is 0-4 mm.

(5) The surface of the weld shall not have cracks, solder tumors and other defects. At first, secondary welds must not have surface air holes, slag, arc cracks, arc scratches and other defects. And the first-stage weld is not allowed to have defects such as bite, unfained, root shrinkage.

Note: Due to the importance of the second-stage weld, the surface air hole, the scrap, the curved crack, the arc scratches should have specific not allowable to the existence of the existence, bite, unfained full, root shrink, etc. The impact is very affected, so the first-level weld must not have such defects.

(6) For welds that need to be preheated or weld heat treatment, the preheating temperature or the postal temperature should be determined by the current standards of the country or by process trials.

The preheating zone is on both sides of the soldering, and the width per side should be greater than 1.5 times the thickness of the weldment, and should not be less than 100 mm; the heat treatment should be carried out immediately after the welding, the holding time should be based on the thickness of each 25 mm Thick 1h is determined.

Note: Welding preheating can reduce the cooling rate of thermal influence zone, and there is an important role in preventing welding delay cracks. The heat treatment of weld is mainly dehydrogenation for weld to prevent the production of cold cracks, and then heat treatment. Timing and The insulation time directly affects the effect of the post-heat treatment, so it should be performed immediately after the welding, and the processing time is appropriately increased.

(7) The quality standards of the secondary and three-stage weld should comply with the provisions of Table 3.4.6. The three-stage docking weld should be performed in appearance quality inspection according to the secondary weld standard.

(8) Welding size allows deviations should comply with the following provisions.

Note: It is strictly forbidden to the dynamic structure, and the three-stage weld should be restricted within a certain range in the second and third-stage weld. The balance of the weld, the opposite, partially welded docking and the angle joint combination weld and the weld pin size of the angular weld, and the remaining high-size dimensional deviations can also affect the load carrying capacity of the steel structure.

(9) Welding the concave angular weld, the weld metal and the base material should be gently transitioned; processing into a concave angular weld, not leaving the cut in its surface.

(10) Weld seam sensation should be achieved: uniform shape, better formation, welding tract and soldering, the soldering path and the basic metallic interchange of transition, welding slag and splashes are basically cleaned.

Five, steel structure welding is the most important knowledge point

Common steel structures are connected to weld connection, bolt connection, rivets, and now continue to share ten most important knowledge points about “welding”.

(1) Advantages of welding connection?

Advantages of welding connection: Simple construction, no weakening of components, easy processing, welding method, can be used, saving steel, high efficiency, large stiffness, good overall, good overall, good sealing performance

Disadvantages of welding connection: The steel metal phase tissue in the heat affects the change in the tissue of the steel, and the local material is brittle; the welding residual stress and residual deformation are presented after the welding, so that the carrier structure is loaded; the welding structure is very sensitive, and the local crack is once It is easy to expand to the whole, and the low temperature is crisp.

(2) Confusion and influencing factors of weldability of steel?

Steel weldability refers to the extent to which materials are easy to weld and meet structural properties under appropriate design and operating conditions. Weldability is often affected by factors such as chemical composition, rolling method, and thickness of steel. In order to evaluate the influence of the chemical composition on the weldability, the ceness is generally used, the smaller the CEQ, the smaller the hardening of the steel, the better the weldability; it is, the larger CEQ, the hardening of steel The larger, the worse weldability is. Carbon equivalent CEQ (%) value can be calculated as follows:

[Prevention and Treatment Method]

[Prevention and Treatment Method]

[Prevention and Treatment Method]

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[Prevention and Treatment Method]

[Prevention and Treatment Method]

[Prevention and Treatment Method]

[Harmful phenomenon]

[Harmful phenomenon]

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[Harmful phenomenon]

[Harmful phenomenon]

[Harmful phenomenon]

[Harmful phenomenon]

When the thick plate multilayer welding .

When the thick plate multilayer welding, the soldering should be welded each at each layer. After each layer of weld welds should be removed, the solder slag, weld surface defects and splashes should be removed, and the defects such as slag, air holes, cracks, and cracks that affect welding quality should be thoroughly removed.

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(3) What is the cause of welding stress and welding deformation and reduce measures?

The welding process of the steel structure is a process of uneven heating and cooling. When welding, the temperature around it is high, and most of the metal is not hot, the expansion and contraction of the body metal is uneven. After cooling, the weld produces different degrees of contraction and internal stress (longitudinal direction and transverse), resulting in various modifications of the welding structure.

In general, the welding stress and welding deformation can be reduced from two aspects of design and processing processes:

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Design measures: reasonable arrangement of weld positions; reasonable selection of weld size; the number of welds should be small, should not be excessively concentrated, and avoid weld stereo interlacing; to avoid shrinkage stress in the thickness direction of the base material.

Process measures: reasonable arrangement of welding order; use reverse deformation; preheating preheating, post-welding back.

(4) Frequent welding method for steel structure?

Steel structure common welding method has manual arc welding, automatic (or semi-automatic) submerged arc welding, gas protection welding.

Manual arc welding: generating an arc after power is energized to melt the wire in the electrode, and drip in a small groove fusion pool blown by the arc on the weld. The slags and gases formed from the electrodes of the electrodes are covered with a molten tank to prevent air from being in contact with the molten liquid metal to avoid the formation of a brittle fracture compound.

A arc welding method for combustion of arc in the flux layer. The welding wire is not applied, but the welding end is covered by the particulate flux under the flux drag, and the arc is completely buried in the flux, the arc heat is concentrated, the melt is deep, suitable for the welding of the thick plate, has very good High productivity, while welding quality is good, the welding is small.

Gas protect welding: An arc welding method using carbon dioxide gas or other inert gas as a protective medium. Relying on the protective gas to form a local protective layer around the arc to prevent intrusion of harmful gases and ensure the stability of the welding process. Weld intensity is better than manual arc welding, plasticity, and corrosion resistance, suitable for welding, advanced method and post-back.

钢结构焊接知识大全

(5) What are the common welding code?

Common welding position, joint form, slope form, weld type and tube structure node form code representation form:

(6) Common welding defects and cause cause and process?

Welds are divided into six categories: cracks, holes, solid inclusions, unfused, unmolved, and shape defects.

crack:

There is usually a heat cracking and cold crack. The main reason for generating thermal cracks is that the material material is poor, the quality of the welding material is not good, the welding process parameters are not properly selected, the welding internal stress is too large; the main reason for the production of cold cracks is that the welding structure is unreasonable, the weld is improper , Welding process measures are unreasonable, such as no preheating in front of welding, and cool after welding. The treatment method is to drill the cleavage metal at both ends of the crack or the solder metal at the cracks.

hole:

It is usually divided into two kinds of porosity and arc-pit. The main reason for generating pores is that the electrode is damaged, the welding rod and the flux are not baked, the base material has oil or rust and oxide, the welding current is too small, the arc length is too long, the welding speed is too fast, and the treatment method is the handling method The weld metal at the air hole is then soldered. The main reason for generating arc pit is too large and the welding speed is too fast, the extinguishing arc is too fast, and the filling metal is added to the extinguishing arc, and the treatment method is to replace it in the arc pit.

钢结构焊接知识大全

Solid inclusion:

There are two flaws of slag and jacket tungsten. The main reason for generating lazas is that the welding material is not good, the welding current is too small, the welding speed is too fast, the density of the slag is too large, and the slag floating, the multilayer welding is not cleaned, the method is to eradicate Weld metal at the slag, then welded. The main reason for generating janitary tungsten is to contact the tungsten and the metal tungs in the argon arc welding, and the treatment method is to dig off the laminated metal and red welding.

钢结构焊接知识大全

Not fused, not welded:

The main reason is that the welding current is too small, the welding speed is too fast, the slope angle gap is too small, and the operation technology is not good. For unfused treatment methods, the welding is removed from the weld metal without fused. For unsubstable treatment methods, no soldering of open-nominal structures, can be sold directly in the back of the weld. For important weldments that cannot be directly welded, the weld metal without welding should be shovel and refolded.

Shape defects: including bite, solder tumor, collapse, root shrink, mistake, angular deviation, high weld, surface irregularity, etc.

(7) Frequent measures to prevent layered tear?

In the T-shaped, cross-shaped and angular joints, when the thickness of the flange plate is not less than 20 mm, in order to avoid or reduce the thickness of the material thickness to receive larger welding recent shrinkage, the following node construction is appropriate:

Under the conditions of welding depth requirements and welds, smaller welding groove angles and gaps (A);

In the corner joint, a symmetry groove or a groove (B) that is biased toward the side panel;

Symmetrical welding in double-sided grooves is used instead of single-sided groove non-symmetrical welding (C);

钢结构焊接知识大全

In the T-shaped or angular join, the plate thickneficial direction with welded stress is extended (D);

In T-shaped, cross-shaped joints, cast steel or forged steel transition segments are used to replace T-shaped, cross-shaped joints (E, F);

钢结构焊接知识大全

Change the force direction of the thick plate joint to reduce the stress in the thickness direction;

Under the node of the static load, under the conditions that meet the coupling strength calculation requirements, the docking combined weld weld seam is replaced by the stagnation welds in the conjunction with the angle joint combined weld.

(8) Weld quality inspection method?

钢结构焊接知识大全

When welding is completed in weld examination, you must first perform an appearance test, observe whether there is a defect with a naked eye or a magnifying glass, such as bite, burning, unmissive, crack, mistake, place, and wait, and check whether the outer dimensions of the welds Require.

The defects in the weld are commonly used ultrasonic detection, which use ultrasonic wave energy to propagate inside the metal, and the principle of reflection and refraction occurs in the interface of the two media, and detect the internal defects of the weld, depending on the waveform. There are defects and defective positions. Since there is a reflective surface between the probe and the detecting member, the coupling agent should be applied to the surface of the weldater when the ultrasonic examination is applied, and the ultrasonic waves cannot determine the type and size of the defect.

Nondestructive testing is sometimes used in ray inspection, and there are two types of X-rays and γ-ray tests. The principle is that when the ray is tested, if there is a defect, the degree of ray attenuation at the defect is small, so the photosens in the back surface of the weld is strong, the film is flush, will be displayed in the defective portion Black spot or stripes. X-ray is short, fast speed, complicated equipment, large cost, small penetration ability, and detected solder thickness of less than 30 mm. Gamma ray inspection equipment is light, simple, and strong penetration ability.

(9) What is the basis for the results of the results when the sample inspection?

When the number of solder seams in N sampling test is less than 2%, the batch acceptance is qualified;

When the number of solder seams in N sampling test is greater than 5%, the batch acceptance is unqualified;

N In addition to this section, the number of sample tests in the sampling test is 2% ~ 5%, and the sampling should be doubled, and the weld extension lines on both sides of the original unqualified part will increase, in all sampling When the unqualified rate in the weld is not more than 3%, the batch acceptance is qualified, and the batch acceptance is unqualified when it is more than 3%;

When the N batches are unqualified, the remaining welds under the batch shall be inspected;

n Check the crack defects when the crack defect is found. When the crack defect is not checked in double sampling weld; the test is passed, and the test is found to be discovered, and the crack defect is found. Unqualified, the full number of the remaining welds should be checked.

钢结构焊接知识大全

(10) What circumstances need to be evaluated by a welding process?

In addition to the conditions of the national steel structural welding norm, the construction unit used steel, welding materials, welding methods, joint forms, welding position, welding heat treatment system, and welding process parameters, preheating and post-hot measures, etc. The combination of parameters shall be evaluated before the production and installation of steel structural components.

钢结构焊接知识大全

The above is the steel structure welding knowledge collected by Guangxi Hongyu Steel Structure, and I hope to help with people need.

This article comes from the network finishing, please contact delete if the infringement please contact!

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