1. Steel structure processing

1.1 Material requirements

The steel must be accompanied by a steel quality certificate. The compressive strength, elongation, yield strength and chemical composition of the steel plates, sections, connectors, fasteners, etc. selected for the steel structure shall comply with the national standards GB1591-2008 and GB/T700-2006. Have a complete factory certificate and inspection report. After receiving the materials, check the material specifications and relevant certificates one by one, and submit the warranty certificate to the owner and supervisor for approval.

The steel should be placed in a prescribed place. It is not allowed to mix materials or components of different types and specifications. In order to avoid large deformation, they should be neatly placed on the shelf for storage.

1.2 Processing

(1) Material correction

① The deformation of the raw material and the deformation caused by processing should be corrected according to the needs.

②In principle, mechanical methods (press machines, etc.) are used for correction, but materials that exceed the mechanical capacity or cannot be corrected by the machine can be corrected by heating. During thermal correction, local heating should be used as much as possible, and the temperature should not exceed 900°C, and forced cooling is strictly prohibited. Measures.

(2) Stakeout and numbering

According to the detailed construction drawing, the real sample will be ejected on the model table at a ratio of 1:1, and the real length will be obtained, and the model (sample rod) will be made according to the real length. Stakeout should use a steel ruler that has been metrologically verified, and the calibrated deviation value should be included in the measurement size. The size division method should first measure the full length and then divide the size, and shall not measure and add in sections to avoid the accumulation of deviations. The sample plate and the sample rod can be made of thin steel plate with a thickness of 0.3～0.5mm.

When setting out, if the size or hole position is found to be inconsistent with the drawings, please contact the owner, supervision and design institute in time to obtain the correct data before blanking. When blanking, first confirm the material mark, and then number the material on the CNC cutting machine according to the parts processing list and layout drawing, and at the same time check the specification, size and quantity of each part. The number of materials is based on the template, and the actual samples are drawn on the materials and marked with various processing marks. The number of materials should use the qualified model (sample rod) to avoid unnecessary losses caused by the direct use of steel rulers or misreading the size.

(3) Cutting

Lock cutting and bevel processing can be machined by a bevel milling machine, or automatic or semi-automatic gas cutting can be used according to the situation.

(4) Hole making

① In principle, high-strength bolt holes, bolt holes and anchor bolt holes are all used by CNC drilling machines, and the connecting plate holes are made on the CNC plane drilling machine. BH and RH section steels are lightly punched with positioning holes (ie foreign punching holes) for subsequent assembly and positioning of connecting plates and other parts.

②The bolt hole made is cylindrical and perpendicular to the surface of the steel material at the position. The inclination is less than 0.5mm, and the hole edge is uniform without cracks or uneven marks. Unless otherwise specified on the design drawing, the general standard is empty. The hole diameter is 0.5mm larger than the bolt diameter.

③The allowable deviation of the aperture size is 0-0.5mm, and the error of ±0.5mm in each group of bolt holes should be within 10%.

(5) Finishing

The pressure surface of the column joint is processed in accordance with the design drawings, and the processing is carried out on the end milling machine, and the pressure contact area is ≥75%.

(6) Treatment of friction surface and screw hole of high-strength bolt connection part

① High-strength bolt holes should be drilled by drilling and grinding.

②The friction surface treatment uses a shot blasting machine to remove the residues such as rolling oxide scale and processing and welding. The surface treatment of the friction surface covers the entire connecting plate and is guaranteed to be more than 2 times the diameter of the washer.

③The roughness of the friction surface treatment should be 95-110μm, and the friction coefficient should be ≥0.55.

1.3 Assembly

(1) Preparation and handling matters before assembly

①Carefully check the number, material, size and quantity of the assembly parts before assembly, and remove the rust, burrs, dirt, etc. within the range of 30-50mm along the edge of the welding seam and the connecting contact surface.

②H-shaped steel is spliced before assembly, and the stiffened plate and connecting plate are finally assembled.

(2) The assembly sequence of H-shaped steel column and steel beam is as follows: Microcomputer lofting → CNC cutting → H-shaped steel automatic assembly → automatic submerged arc welding → flange straightening → three-dimensional numerical control hole → automatic band saw machine cutting → groove opening milling Machine H-shaped steel groove → stiffened plate and connecting plate assembly welding → H-shaped steel column straightening → sandblasting and rust removal → painting → packaging and shipping.

(3) The allowable deviation of welding connection assembly must be implemented in accordance with the welding process card, and meet the requirements of GB50205-2001 "Code for Acceptance of Construction Quality of Steel Structure Engineering".

(4) All base plates, splicing plates, cover plates and reinforcement plates are welded to the structural members in the processing plant, and bolt holes are drilled. The factory prefabrication of the web shall be positioned in the punching holes of the tie rod support and the flange support.

2. Steel structure welding

Welding adopts carbon dioxide shielded welding and manual arc welding. Welding rods and other welding materials must meet the design requirements, and the welding quality should meet the requirements of national standards. The inspection of welds shall be carried out according to the design requirements.

Process flow

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

Arc welding of steel structure:

1. Flat welding

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

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

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.

1.4 Welding current: According to the thickness of the weldment, welding level, electrode type, diameter, welder's proficiency and other factors, select the appropriate welding current.

1.5 Arc ignition: the starting and falling arc point of the fillet weld should be at the end of the weld, which should be greater than 10mm, and should not be arced casually. The electrode should be pulled away from the weld area immediately after ignition and arc start to keep the electrode and the component between 2 ~

An arc is generated in a gap of 4mm. 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.

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

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

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 forward direction is 60～75°; the other is the angle between the electrode and the welding left and right. When 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 different, the angle between the electrode and the thicker weldment should be greater than the angle between the electrode and the thinner weldment.

1.9 Retracting arc: 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.

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.

2. Vertical welding: The basic operation process is the same as that of flat welding, but the following issues should be paid attention to:

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

2.2 Adopt short arc welding, the arc length is generally 2～3mm.

2.3 The angle of the electrode 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.

2.4 Retracting arc: 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. 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 electrode, the electrode should be inclined downward during horizontal welding, and its angle is

70°～80°, to prevent the iron from falling under the water. 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°.

4. Overhead welding: 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 is at an angle of 70° to 80° with the welding direction. It is appropriate to use small current and short arc welding.

5. Winter low temperature welding: When arc welding is performed 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 so that the weld and the heat-affected zone are slowly cooled. 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. In order to prevent welding cracks, the steel structure 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.