Qingdao KXD Steel Structure Co., Ltd

Quality Assurance&Control Policy, Quality Objectives

QA&QC Policy:

To establish a standardized steel structure manufacturing enterprise, pursue excellent quality, meet customer needs, and achieve continuous improvement.

QA&QC goal:

Product delivery pass rate ≥ 90%

Customer satisfaction ≥ 90%

QA&QC of all-round stage of steel structure fabrication:

I. RAW MATERIAL INSPECTION PRECEDURE

1.1 Steel plate acceptance

verify the mill certificate,heat/batch number, product name,quantity, spec, weight,quality, technical condition to see if they are up to the requirements；check the plate size, thickness,mark and surface quality；re-inspect the chemical composition and mechanical performance of the plates for each heat No.。When there is no rules for material inspection in the contract and technical condition,batch sampling should be conducted.The inspection quantity and steel should be up the requirements of design and JGJ81-2002 Technical specification for welding of steel structure of building. 

After the steel arriving at the factory, the material procurement department provides a list of materials arrival and inspection notice to the quality inspection department. After receiving the notice, the quality inspection department organizes the acceptance of steel item by item according to the inspection content, and the re-inspection of the steel is carried out in batches according to the batch number of the furnace.

1.2 Acceptance of steel tube,welding material and painting material

The steel pipe shall be inspected in batches for sampling and re-inspection of the incoming steel pipe inspection batch (same steel production, same quality grade, same delivery state, same edition number, same thickness specification). The steel pipe size, nozzle ovality, shape Allowable deviation, appearance quality of steel pipe surface, etc. shall be implemented in accordance with relevant national standards.

The type, specifications and performance of welding materials shall comply with the current national product standards and design requirements. The welding materials used in steel structure engineering shall be selected according to the design requirements, and the products shall meet the requirements of the corresponding national current standards.

The welding materials used in important steel structures shall be re-inspected by sampling, and the results of re-inspection shall comply with the current national product standards and design requirements. Since the quality of different production batches often has certain differences, the re-inspection of welding materials used for important steel structure engineering is clearly defined. The retest shall be a witness sampling and sample inspection project. “Importance”refers to：

①First- and second-level welds with a first-grade safety rating. ②Level 1 weld with a safety rating of 2.

1.3 Welding procedure qualification

In order to ensure the welding quality of the project, the company's technical process department will do a good job in welding process evaluation according to the JGJ81-2002 standard and the bidding documents in the "Technical Specifications for Welding of Steel Structures of Buildings", and formulate perfect and feasible welding process plans and measures which function as a process specification for guiding welding operations in engineering.

Welding procedure qualification rules

The following is the welding procedure qualification rules of JGJ81-2002 "Technical Regulations for Welding of Building Steel Structures".

In accordance with the provisions of the welding procedure qualification test of JGJ81-2002 of the Welding Procedures for Building Steel Structures, our company has done the corresponding welding evaluation for the conditions defined in the welding procedure qualifications to be considered in this project. The assessment covers all the welding evaluation requirements of the project. Therefore, in the implementation, we will submit the relevant information to the supervisory party for approval and the welding procedure qualification plan can be exempted.

1.4 Steel structure general production process measures

According to the structural characteristics and technical requirements of the engineering components, combined with the processing technology applicable to the processing of the engineering components, the general process of steel structure production is as follows：

According to the characteristics of the steel structure of this project, there are the following general-purpose processes, and acceptance is carried out according to the corresponding standard of GB50205-2001 "Code for Construction Quality Acceptance of Steel Structure Engineering".

1.5 Steel plate correction

The thickness of the steel plate of this project is 3~50mm. We will use the WC43-100x3000mm steel plate leveling machine, one of the company's superior equipment, to level the engineering sheet.

The machine can level the metal sheet with the material yield limit below 420Mpa in the cold state, which can ensure the precision of the board blanking and also effectively reduce the rolling stress of the board. Performance can be corrected for sheet thickness: 8-28mm, leveling roll width: 3000mm. Leveling accuracy: flatness ≤1.5mm.

Steel leveling is an important process measure to ensure component accuracy.

Since the unevenness of the steel plate manufacturing standard has different allowable ranges for different plates, it is not enough to ensure the manufacturing precision of the components; at the same time, deformation is easily caused during transportation, lifting and stacking, so the steel plate needs to be leveled.

In addition, during the cutting process, the cutting edge receives a large amount of heat and a fast cooling speed, so there is a large shrinkage stress at the cutting edge; therefore, before the processing and assembly, in order to ensure the assembly and welding quality, all the parts are used first. The leveling machine first performs leveling treatment so that the flatness of each part is controlled within 1 mm per square meter.

1.6 Stakeout and numbering

1）Steel tape measure, theodolite and other measuring tools used for stakeout, cutting, production, and acceptance must be inspected by the metrology unit at or above the municipal level. Measurements shall be based on a certified steel tape measure (100 m) with an errata size for verification with the supervisor and installation unit.

2）All components shall be computerized to verify the geometric dimensions of all components in accordance with the requirements of the detailed design drawings and manufacturing processes. If it is found that there are omissions or errors in the construction drawing, and other reasons need to change the construction drawing, the design change notice of the original design unit must be obtained, and it is not allowed to modify it without authorization; after the completion of the stakeout work, the enlarged sample and the sample rod and sample ( Or the blanking diagram) to carry out self-inspection, and report to the full-time inspection personnel for inspection after the error is confirmed. After the sampling inspection is passed, the necessary angles, notches, prototypes and frame samples can be made according to the process requirements.

3）Lining tolerance requirements：

4）The baseline, centerline, and inspection control points should be indicated after marking. Do not use a tool such as a chisel when marking, a small amount of the marking should be no more than 0.5mm in depth, and no permanent markings should be left on the steel plate.

5）Before the material is confirmed, the material and familiarity with the process requirements should be confirmed, and then according to the layout drawing, the blanking processing list and the part sketch.。

6）The base material must be straight and free from damage and other defects, otherwise it should be corrected or eliminated first.。

7）The allowable deviation of the material is shown in the table below.

8）Marking-off quality control

1.7 Cutting

1）Selection of cutting tools

Because the thickness of this project is 3~50mm, combined with the company's factory equipment, flame cutting。

2）Before cutting, the oil, rust and moisture on the surface of the base metal should be removed; after cutting, the gas cutting surface should be smooth and free of cracks, the slag and gas sample should be removed, and the shearing edge should be polished.。

3）Consider the kerf compensation during the cutting process. The cutting allowance is shown in the table belows：

4）Gas cutting tolerance requirements：

5）The process parameters have a great influence on the quality of gas cutting. The relationship between common gas cutting section defects and process parameters is as follows.：

Defect type	Cause	Graphical description
Rough cut surface	a, cutting oxygen pressure is too high b, improper use of the cutting nozzle c, cutting speed is too fast d, preheating flame energy is too large
Cutting surface gap	a, the cutting process is interrupted, the re-starting is not good b, the surface of the steel plate has a thick scale, rust, etc. c, the cutting machine is not walking smoothly
Cut surface concave	a, cutting oxygen pressure is too high b, cutting speed is too fast
Cutting surface tilt	a, the torch and the board surface are not vertical b, the wind line is skewed c, cutting oxygen pressure is low or the mouth number is small
The surface of the cutting surface is beaded	a, the surface of the steel plate has oxide scale, rust b, the distance from the cutting nozzle to the steel plate is too small, the flame is too strong
Melting surface edge melting	a, preheating flame is too strong b, cutting speed is too slow c, the cutting nozzle is too close to the plate
Lower edge of the cutting surface	a, cutting speed is too fast or too slow b, the cutting mouth number is too small c, cutting oxygen pressure is too low

6）The cutting slag should be removed after cutting. For surfaces that cannot be finished after assembly, such as the inner surface of the curved lock, it should be treated before assembly. The right angle cut in the drawing should be a 15mm arc transition (such as a trabecular end wing web cut). If the H-beam is welded, the arc of R=15mm should be opened at the intersection of the wing webs to make the wing penetrate.

7）After the flame is cut, the size of the part must be self-checked, and then the work order number, component number, and part number of the part must be marked, and then the quality inspector will check the various indicators, and then pass the next process.

8）Milling parts are required, and 5 mm machining allowance is required for each milling edge；

9）Allowable deviation of planing

1.8 Welding H-shaped steel processing and manufacturing process

 

   

No.	Process	Craftsmanship
1	Pre-treatment, leveling and cutting of steel plates
		1) Pre-treatment of the steel sheet is required before cutting the steel sheet to remove the oxide layer on the surface of the steel sheet to improve the compactness of the surface of the steel sheet and ensure the welding quality. 2) Cutting steel plate cutting adopts precision numerical control flame steel plate cutting machine.
2	Steel plate Docking
		Semi-automatic precision cutting of steel plate butt joints, semi-automatic submerged arc welding of steel plate butt welding
3	T section production
		The T-shaped group is set up on the automatic forming machine of the H-shaped steel production line to ensure the verticality of the web and the flange plate of the T-shaped group to meet the design requirements. After the assembly, the temporary fixing is carried out, and the fixed method is fixed by the additional process plate method.
4	H section assemble
		The H-beam assembly is set up on the imported H-beam production line. Four hydraulic positioning systems are used to position the upper and lower flange plates and webs of the H-shaped steel members. The parallelism of the flange plates and the verticality of the wings and webs are adjusted. Degree and then fixed; fixed welding using CO2 gas shielded welding.
5	H section welding
		H-beam welding is carried out on the H-beam automatic production line for automatic submerged arc welding. The qualified H-shaped steel members are hung on the boat-shaped tire frame, the welding position is adjusted, and the welding is fixed. The welding is performed by symmetric welding sequence.
6	H-beam Correction
		After the four main welds of H-beam are welded, the heat generated by the welding is difficult to release at one time; however, the welding stress is deformed, so the parallelism of the flange plate is ensured after the components are welded. Correction of H-beam is required. Correction on the corrective machine on the H-beam automatic production line.
7	H-beam measuring
		H-beams need to be measured after forming. The measurement is mainly the parallelism of the flange plates, and the perpendicularity of the flange plates to the webs meets the design requirements.
8	H-beam drilling, end face machining
		The H-beam is drilled after forming, and the drilling is processed on the imported automatic three-dimensional CNC drilling machine to ensure that the hole spacing meets the design requirements; since the engineering structure is a high-rise steel structure, the end face machining is an important quality factor to ensure the steel structure docking. End face machining mainly performs milling on the end face milling machine. Make sure the parallelism of the faces on both ends.
9	Component shot blasting	After the component is finished, it will enter the shot blasting and embroidery process. The shot blasting and embroidery will mainly adopt the imported eight-head automatic shot blasting machine.
10	Component identification, storage	Mark the component number positioning mark and the like in the specified position according to the process regulations. When the rods are stored, care should be taken to protect them. The lower layer of sleepers should be used to pay attention to the deformation of the components when stacking.

1.9.Welding quality control content

According to the basic idea of TQC, we will do a good job in all aspects of quality management, and ensure the quality of the project.

Quality management content and defect relationships