Descriptions of the lofting process: 
1. Carry out lofting of the steel-tower structure with AutoCAD on the computer according to the drawings from the designing institute. 

2. The purpose of the lofting of structure dimensions is to check the installation dimensions of the working drawing. 

3. The purpose of joint lofting is to check the installation joint, such as the contact between structures or components on the joint and the installation dimensions and construction dimensions of structures. 

4. Fabrication processing card, assembling operation card and component diagram shall be fabricated, on which the profession, procedure, precision, tolerance and the processing label shall be stated. 

Descriptions of the marking process: 

Inspect the raw materials according to the fabrication processing card to see whether the material is subject to requirements on the card, such as the dimensions, material and size of the material. Inspection shall be carried out on the appearance and rustiness of the material, after which is passed, the raw materials shall be extracted according to the operation card. 

Description on the model fabrication process: 

Use esquadro, ruler, scribing compass and scriber to draw pictures integrated by the dimensions of the processing card on the model (iron material model) and then inspect the picture. When the inspection is passed, use the scriber to print the corresponding steel seal number on the location of the hole and cut it along the line with iron scissor at last. The scissor shall be vertical to the model with the up and down blade close. More models shall be made with large batch size. One model shall be made for each 20 pieces. Requirements of fabrication of the model shall be as follows: 

Descriptions of the blanking process: Different blanking equipment shall be used according to the dimensions and specifications of the component fabrication processing card compiled by the technical department.

1. For components with the thickness no less than 14mm, the CNC flame cutting machine shall be used for blanking.

(1) Programming: the steel plate shall be programmed according to the processing card at first, and then the steel plate shall be put in. Ranging item shall be selected to check whether the basic dimensions of the components are identical to the previous. The programming shall be reformed when not identical and the next step shall be carried out only after the inspection is passed.

(2) Selection of the cutting distance: check if the selected cutting distance is suitable and the working conditions are favorable. Selection of the cutting torch model is as the following table:

(3) Fire adjustment: Adjust the fire after selection of cutting distance to make it subject to the cutting requirements and the data after cutting torch line or the cylinder is straight the fire is well adjusted.

(4) Start cutting after the above operation is finished and the cutting speed shall be as the following table:

(5) After cutting is finished, clean the iron oxide and slags, and then carry out the compact point and carry out post self-inspection with 5m and 20m tape measures. When the self-inspection is passed, special quality inspector shall use the same tool to carry out special examination according to the Inspection Standards of Oxygen-acetylene Cutting. The next procedure shall only be carried out after the inspection by the special quality inspector is passed

.Attachments: Inspection Standards of Oxygen-acetylene Cutting The perpendicularity of the cutting edge is less than t/8 and no larger than 2.0mm (t stands for the thickness of the plate): length: 0-1mm Width: ±0.1mm; diagonal line: ±0.1mm; local open < 1mm; tolerance of the drift pin ±0.5mm

Process parameters cutting mild steel with regular boost cutter:

Screw the adjusting nut to make the interval proper and check the level difference between the blades, which shall be 1-2mm. Use the special plate to adjust the journey of the sliding block on the press machine. Start blanking after the adjusting is finished. Put the steel plate into the shearer and align the model line. Start the cutting switch to cut the material. The material picker shall pick the cut materials and put them in the waste basket and then put all the used workpieces and materials neatly on the lining platform and attach the model. Turn off the motor and cut off the power after the shearing is finished.

Descriptions of the lineation process:

Use lineation plate, slate pencil, the model and the bishop to scribing on the workpieces. Put the workpiece on the workpiece on the lineation plate at first with the reference edge closely attached to the bottom rod of the lineation plate and tile the model on the workpiece and press item level. Drill holes with drift pin at the center of the borehole of the model with the depth of the hole ≥1mm and the diameter ≤1mm. After punching successively, check whether the first punching point is moved. Carry out the workpiece inspection if not moved and after the inspection is passed, carry out lineation and punching point in batches. Carry out spot check on the workpieces of volume production, in case of deformation or displacement of the model leading to wrong workpieces. 

Descriptions of the turning process:

Turn the flanges in the blanking with the vertical or horizontal lathe according to the requirements on the processing card. Quality standards of turning of the flange: allowable tolerance on the external diameter of the flange plate is ±0.2mm, the internal diameter is 0+2mm and the end face is ±0.5mm. 

Descriptions of the drilling process:

Description of the drilling process on linking board

Different drilling machine, bit and jig shall be selected according to the fabrication processing card. Put on the drill bit and start the drilling machine. Use the special wrench to adjust the route of the drill bit to proper location to drill through the dead plate and fix the workpieces on the workpiece platform with clamps to make holes. After drilling, move the drill bit and check whether the workpiece is qualified. After confirmation, make holes in batch. After drilling the workpieces, turn off the power, clean out rags on the workpiece and put them away neatly.

Requirements of hole drilling: Allowable deviations for Class C bolt bores (mm)

Allowable deviations for bolt hole's pitch-row (mm)

Note: 

(1) All the bolt holes in node with connecting plate connected with the same rod member belong to one group.

(2) All the bolt holes with butt joint on the same side of splicing plate belong to one group.

(3) All the bolt holes between two adjacent nodes or joints with those specified in the above two articles excluded belong to one group.

(4) For connecting bolt holes in the flange of flexural members, all the bolt holes within one meter belong to one group.

different drilling machines according to the fabrication processing card and choose different drill bit and jig according to the size of the hole. For larger holes, make aΦ10 hole. And then make the required hole on the 80 drilling platform, with the requirements of holes drilling as follows:

Descriptions of the steel seal process: 

Print the steel seal with the friction press machine according to the component steel print number stated in the fabrication process. Make the steel print number with different steel print number moulds and fix them on the press mould to print the steel print number on proper location of the component for the convenience for production and installation. After the printing of the first piece is perfect, carry out the steel seal pressing in batch and check whether the steel moulds are complete from time to time. Make the steel seal number with different steel print number moulds according to the steel print number stated on the fabrication processing card of the component and fix them on the press mould to print the steel print number on proper location of the component. 

Leveling

300 t double plate friction press machine J53-300 type, 500 t four-column hydraulic press and leveling die are mainly used to level the workpiece. First of all, appropriate machinery and leveling die shall be chosen according to the fabrication processing card and compression bar stroke shall be adjusted. Then feed the workpiece into the leveling die and level the workpiece. After leveling, use the steel ruler as a measuring tool for inspection. 

Unevenness requirements are shown in the following table:

Description of edge fabrication process: 

δ is larger than 30mm, the flame cutting processing method shall be adopted. 

When machining the slab edge, the operator shall process in strict accordance with the contents specified in the processing card. First of all, the operator shall clean the rust, oil, etc. on the steel surface which is within 50mm from the cutting edge, then put the lead rail parallel with the cutting edge and light the fire, adjust the angle and start cutting. 

Before flame cutting, the operator should carry out cutting test and use the welding ruler after the cutting test to check whether it is qualified, if not qualified, it should be adjusted to qualify before edge cutting. During the cutting process, the operator shall measure it by a welding inspection ruler from time to time, in order to ensure the processing angle of the edge and the dimension of the blunt edge. Clean the iron oxide and slag after processing. 

The operator shall use a welding inspection ruler for self-inspection, if it is qualified, the full-time inspectors shall use the same tool and carry out special inspections according to the Inspection Standard for Edge Preparation. 

If δ is no more than 30mm, the rolling shear chamfering machine shall be adopted: 

During operation, adjust the plate thickness and angle according to the processing card, then carry out trial processing by the sample plate, if the processing inspection is qualified, then process the plate. After the processing, the operator shall use a welding inspection ruler for self-inspection, if it is qualified, the full-time inspectors shall use the same tool and carry out special inspections according to the Inspection Standard for Edge Preparation. 

3 Inspection standard: Inspection Standard for Edge Preparation (excerpt) 

Truncated edge: ±1.0mm, edge angular deviation is 3 degrees and there is no oxide, fused tumor and splash on the edge after cutting; the processing surface has no step during machining processing. 

The next procedure shall only be carried out after the inspection by the special quality inspector is passed. 

Galvanizing process description 

Cage-putting

According to the different parts and components and corrosion condition, they shall be loaded into respective cage: angle steel and steel pipe shall be loaded into their respective special cage; for particularly large components such as column and tower beam, the cage loading of individual component shall be carried out; the connecting plate, clamping plate and cover plate shall be loaded into their special cages. During the loading, there should be a gap between two components and parts and the gap should not be too small. For components loaded into the grid, there should be one component in one grid, two or more components in one grid is prohibited. And the same component shall be in the same plane, one should pay attention to the deformation according to the characteristics of the components. In hoisting, the hoisting node shall be set or the node shall be appropriately added according to the size of the cage and the component, in order to prevent the deformation of the component due to the bad node. 

Water cleaning 

When the workpiece is washed, the crane and hanger shall move up and down two times in the water, and the sediment sundries on the surface of the workpiece are washed. 

Alkali cleaning

If there are paint, oil on the surface of the workpiece, acid cleaning crane hanger shall undergo alkali cleaning in the alkali pool. The analyst is required to control the content of NaOH in the alkali liquor in 60-90, the temperature of the solution should be between 60℃ to 100℃ and the testing result shall be filled out in the Analysis Report on the Zinc Plating Solution. 

Water cleaning

The workpiece after alkali cleaning shall be washed by water in the pool, the lye on the surface of the workpiece shall be washed off. In washing, the crane hanger shall move up and down in the water for 2 to 3 times to make sure that there is no lye on the workpiece surface. 

Acid cleaning (HA) 

Acid cleaning temperature shall be kept in room temperature in summer and 15℃ to 25℃ in winter. The technician should adjust the temperature of the solution by closing the vapor or increasing the vapor pressure. The analyst shall test the acid salt and ferrous ion in acid liquor per shift, 4% to 31% concentration of hydrochloric acid is normal, and if the ferrous ion concentration in hydrochloric acid is within 200%, it means the normal level. The testing results shall be filled out in On-site Testing Report of Galvanizing Solution; it shall be classified into three categories according to the different corrosion degree of the workpiece. 

①Serious corrosion 

The hammer is used to knock off the workpiece, the rust layer is obviously peeled off and the surface is uneven. If you touch the workpiece by hand, the hands will be stained with brown powder. The acid cleaning time is 2 to 4 hours. 

②Normal corrosion 

The workpiece has no obvious peeling when it is knocked off by a hammer. If you touch the workpiece by hand, the hands will be stained with brown powder. The acid cleaning time is 1 to 2 hours. 

③Mild corrosion 

The workpiece surface is smooth and offwhite, the general acid cleaning time is 30 to 60 minutes. In acid cleaning, it is required to shake the pool in every 20 minutes (shake by crane hanger in the pool for 2 to 3 times), in order to speed up the acid cleaning of the workpiece. At the same time, the acid cleaning condition shall be checked to avoid over-acid cleaning. Offwhite workpiece surface means the acid cleaning is qualified. 

Water cleaning 

The workpiece shall be washed in the water tank after the acid cleaning is qualified, it shall be put into 2# tank after being washed in 3# tank. During cleaning, the crane workpiece shall move in each pool for 2 to 3 times and the residual acid cleaning on the workpiece surface shall be fully washed off. The tank solution is kept at room temperature and the solution in each tank is required to change once a day. 

Plating assistant (1#) 

The help bath temperature is controlled between 55℃ to 75℃, and the temperature of the solution is controlled by the technician by reducing and increasing the vapor pressure. The analyst is required to test the content of NH4CL, ZnCL2 and ferrous iron in plating groove one time each shift, the content of NH4CL shall be generally controlled between 120 to 180g/L, the content of ZnCL2 shall be controlled between 70 to 120g/L, and the testing results shall be filled out in On-site Testing Report of Galvanizing Solution and Galvanizing Infiltration Record. The NH4CL and ZnCL2 solution in it shall be adjusted by technologist by adding NH4CL, ZnCL2 and water in accordance with testing results, German formula is adopted in the solution. 

Hanging 

After plating, the workpiece shall be hanged again. During hanging, the workpiece cannot be attached to each other. The cage width of the workpiece shall be about 1.5 m, gas deduction and zinc leakage are not allowed. In hanging, the selection of hanging points shall be noticed. For longer workpieces, there should be more hangs at 1/4 of both ends to prevent the deformation when putted into the pot.

Furnace drying

The drying furnace temperature shall be controlled in 100℃ to 200℃, the dryer worker shall control the furnace temperature by opening or reducing the flue valve, the drying time is 10 to 20 minutes. 

Zinc galvanizing 

In normal production, the zinc temperature is generally between 440℃ to 460℃ and it is controlled by the gas automatic control system. When the workpiece is entering the zinc liquor, the boiler can scrap the zinc ash on the zinc liquor surface. After the workpiece is in the zinc liquor, the boiler shall shake it with a hand hook. The zinc immersion time shall be controlled according to different thickness and width of the workpiece: 80 s to 240 s zinc immersion time for workpiece with thickness greater than 5mm, 70 s to 120 s zinc immersion time for workpiece with thickness smaller than 5mm, so that the zinc thickness of the workpiece can reach national standard. 

Cooling (11#) 

After the galvanizing treatment, the workpiece shall be cooled in water, the water temperature in tank shall be lower than 60℃, and the technologist shall reduce the temperature by circulation water. The cooling time of normal workpiece is about 2 min, and for large-sized workpiece, it can be appropriately extended for 20 s to 30 s so that the zinc can be completely cooled. 

Passivation

Passivation is needed in workpiece cooling, the duty analyst is required to test the content of CaO3 in the passivation solution, and the content of CaO3 in 3 to 5g/L is qualified. The testing results shall be filled in Record Report on On-site Galvanizing Testing, the concentration of the solution is controlled by the analyst by adding water or CaO3, and the passivation time of the workpiece is 60 s to 100 s. 

Poaching

The workpiece shall be rinsed after passivation, the crane hanger shall move up and down for two times in the pool so as to clean the CrO3 residue on the workpiece, the rinse water shall be replaced once a week. 

Sorting

The operator shall smooth the end lutetium and zinc tip with an iron file to ensure the surface of zinc workpiece is practically smooth. The quality inspector shall carry out quality inspection on the plating according to GB2694-81. 

① Galvanized adhesion and zinc layer thickness - the wall thickness of plating shall be less than 5 mm, zinc adhesion should not be less than 460 g/m2, that is, the zinc layer thickness shall not be less than 65 μm; if the zinc workpiece thickness is bigger than 5mm, zinc adhesion is no less than 650g/ m2, that is the zinc layer thickness shall be no less than 90 μm, under special circumstances, the thickness of the zinc layer shall be determined according to the requirements. 

② Uniformity: the zinc layer of the plating shall be etched for four times with copper sulfate solution and without iron exposure. 

③ Adhesiveness: galvanized zinc layer should be combined with the base metal firmly for hammer test, the zinc layer does not peel off or raise.