Quality Control

Formulate Production Processes

1. Determine product requirements: Clarify the specifications of the flange (such as size, thickness, aperture, etc.), material (choose suitable metal materials according to the usage environment), performance requirements (such as strength, toughness, corrosion resistance, etc.), and production quantity.

2. Choose forging method: Determine whether to use free forging or die forging based on the complexity of the product's shape, precision requirements, and production batch size. Free forging has strong flexibility and is suitable for single piece small batch or large flange production; Forging has high precision and fast efficiency, suitable for mass production.

3. Raw material preparation: Purchase raw materials that meet design requirements and inspect their chemical composition, hardness, and other indicators to ensure quality compliance. Calculate the weight and size specifications of the required raw materials based on the flange size, and cut and cut the material.

4. Heating process: Determine the appropriate heating equipment (such as a heating furnace), set the heating speed and temperature range based on the material characteristics, ensure that the billet is uniformly heated to the appropriate forging temperature, and avoid overheating or overburning.

5. Forging process: If it is free forging, establish the sequence and parameters for upsetting, stretching, punching and other operations; Die forging requires the design and manufacture of high-precision molds, as well as the determination of forging pressure, number of forging cycles, and other parameters to ensure good flange forming, while controlling the forging ratio to optimize the internal organizational structure.

6. Cooling and heat treatment: Select appropriate cooling methods (such as air cooling, furnace cooling, etc.) based on material and product performance requirements, and then carry out corresponding heat treatment processes (normalizing, tempering, quenching and tempering, etc.) to improve the mechanical properties of the material and eliminate residual stress.

7. Subsequent processing and handling: This includes surface cleaning of flanges (removal of oxide scale, etc.), mechanical processing (precise machining of sealing surfaces, bolt holes, etc.), and finally quality testing (non-destructive testing, dimensional accuracy testing, performance testing, etc.) to ensure that the product meets quality standards. Non conforming products are repaired or scrapped, and production process details are improved to continuously improve product quality and production efficiency.

Purchasing

Material selection: Select suitable metal materials such as carbon steel, alloy steel, stainless steel, etc. based on the usage requirements and performance characteristics of the ordered products, and ensure that the quality of the materials meets relevant standards and specifications.

Raw Material Entry Inspection

When raw materials enter the factory, strict inspections are required, including appearance, chemical composition analysis, mechanical property testing, metallographic structure inspection, etc., to ensure that the quality and performance of the materials meet the production requirements of customer orders.

Material Cutting

Cut the raw materials into suitable billet sizes according to the size and shape requirements of the ordered products. The cutting method can be sawing, shearing, flame cutting, etc.

Forging Production

Heating of raw materials:Place the cut billet into a heating furnace for heating to reach the appropriate forging temperature range. The heating temperature and holding time required for different metal materials and forging shapes vary.

Forging operation:Use forging equipment (such as clamp hammers, air hammers, ring mills, friction presses, hydraulic presses, etc.) to apply pressure to the heated billet, causing it to undergo plastic deformation, in order to obtain the desired forging shape and size. The forging method includes basic processes such as free forging, die forging, upsetting, stretching, bending, etc. The appropriate forging method can be selected according to the complexity of the forging and the production batch.

Forging ratio control:During the forging process, it is necessary to control the forging ratio, which is the ratio of the cross-sectional area of the billet before and after forging. A reasonable forging ratio can improve the microstructure and properties of metals, enhance the mechanical properties and quality stability of forgings.

Cooling after forging:After forging is completed, choose the appropriate cooling method based on the material and performance requirements of the forging, such as air cooling, air cooling, water cooling, pit cooling, etc. Different cooling methods can affect the microstructure and properties of forgings, such as hardness, strength, toughness, etc.

Rough Machining

Remove excess:Quickly remove most of the excess metal on the forging blank, making the shape and size of the forging close to the final product, leaving 0.5-1mm of machining allowance for subsequent precision machining, allowing the product performance and internal crystal structure to reach the optimal state during heat treatment, and greatly improving the efficiency of precision machining.

Defects discovered:During the rough machining process, it is possible to timely expose defects such as sand holes, air holes, cracks, etc. that may exist in the forging blank, which facilitates timely repair or decision to scrap, and avoids wasting more time and costs in subsequent processing.

Release stress:During the forging process, residual stress is generated in forgings. Rough machining can remove some of the material, release the stress to a certain extent, and reduce the risk of deformation and cracking caused by stress concentration during subsequent processing and use.

Heat Treatment

Select different heat treatment methods according to customer order technical requirements or corresponding material standards to achieve optimal mechanical performance of the product.There are several common heat treatment methods, including:

Normalization or Annealing:Generally, after forging, some factories choose normalizing, while some companies choose annealing, in order to refine grain size, achieve uniform structure, eliminate internal stress, improve the cutting and mechanical properties of forgings, and prepare for subsequent processing and handling.

Quenching and tempering treatment:For some forgings with high requirements, such as shafts, gears, etc., quenching and tempering treatment is usually required, that is, quenching and high-temperature tempering. Quenching and tempering treatment can improve the comprehensive mechanical properties of forgings, enhance their strength, toughness, and fatigue life.

Quenching and tempering:According to the specific requirements of the forging, quenching treatment is carried out to improve surface hardness and wear resistance, followed by tempering treatment to eliminate quenching stress, stabilize the structure and properties, and prevent deformation and cracking of the forging during use.

Sampling & Testing

1、 Sampling of test bars from the same furnace:

Sampling of test bars from the same furnace is a key step in the quality control process of metal materials, used to ensure that the quality performance of the entire furnace of metal products meets the expected standards.

Sampling purpose:

Ingredient verification: Verify whether the chemical composition of the metal melt accurately meets the design formula requirements. Taking alloy steel as an example, it contains multiple alloying elements. Sampling and analysis of the same furnace test bar can confirm the proportion of each element, avoiding the scrap of the entire furnace product due to ingredient errors.
Performance estimation: By conducting mechanical performance tests on test bars, such as tensile, impact, and hardness tests, the performance of actual production parts in the same furnace can be inferred in advance. For example, the mechanical properties of engine cylinder block castings can be estimated based on yield strength, tensile strength, and other data obtained from bar tensile tests.
Quality traceability: Fully retain the same furnace test bar samples and corresponding testing data. Once there is a quality problem with the finished product, it can be traced back to find the cause, whether it is due to melting, casting, or subsequent processing errors.

Sampling location and quantity:

Location: For casting processes, samples are often taken at the middle and lower parts of the ladle, where the metal liquid is relatively evenly mixed and can represent the composition of the entire furnace; During forging, samples should be taken from both the head and tail ends of the billet, as there are differences in the degree of deformation and temperature distribution at both ends during the forging process. Sampling from multiple locations can provide comprehensive coverage. If continuous casting is used, samples will be taken from the starting, middle, and ending sections to monitor the quality of the entire process.
Quantity: Generally, for small melting furnaces, at least 3 test bars are taken from each furnace, while for large industrial furnaces, the number is correspondingly increased. Taking multiple test bars is not only to reduce errors in parallel testing, but also to ensure smooth testing in case of any processing errors in one of the test bars.

Sampling method:

Casting method: Directly pour the molten metal into a specially designed test bar mold and let it cool and solidify into shape. This method is simple and direct, and can restore the original state of the melt to the greatest extent possible. However, the mold needs to be preheated and coated with release agent in advance to prevent defects such as porosity and mold sticking in the test bar.
Cutting method: For already formed castings and forgings, cutting equipment such as band saws and grinding wheel cutting machines are used to cut suitable sized test bar blanks from the matrix. When cutting, the cutting speed and feed rate should be controlled to avoid overheating affecting the microstructure of the test bar, and then polished to standard dimensions.

Test bar processing:

Dimensional accuracy: Processing raw test bars to precise standard dimensions, such as tensile test bars, with strict tolerance requirements for the diameter and length of the gauge length section. Any deviation will interfere with the mechanical performance test results. High precision equipment such as CNC lathes are commonly used during processing, which are monitored in real-time with measuring tools such as micrometers and vernier calipers.
Surface quality: The surface of the test bar should be flat and smooth, without obvious scratches or sand holes. Surface defects not only interfere with testing accuracy, but may also become stress concentration points, leading to premature failure of the test. So, after processing, it is often necessary to go through processes such as sanding and polishing with sandpaper.

Marking and recording:

Marking: Clearly mark key information such as furnace number, sampling location, and sampling time on the test rod, usually using steel seal marking and electrochemical corrosion marking to ensure that the marking is firm and durable, and not eroded by subsequent testing processes.
Record: Establish a detailed sampling record file synchronously, covering the above marked information, as well as details of melt ingredients, sampling operators, processing parameters, etc., to facilitate subsequent traceability, query, and data analysis.

2、 Maternal sampling:

Sampling principle:

Representativeness: The sample taken should be able to represent the overall quality condition of the forging matrix, including its microstructure, mechanical properties, etc. For example, to test the overall strength of forgings, it is necessary to avoid sampling only from the edges or local defects of the forgings, and instead select parts that can reflect the average performance of the forgings.
Randomness: On the basis of ensuring representativeness, sampling should have a certain degree of randomness to avoid the influence of human factors on the results and ensure the objectivity and reliability of the test results.
Feasibility: The sampling method and location should be determined based on the actual shape, size, and processing technology of the forging to ensure the operability of the sampling process and minimize damage to the forging matrix.

Sampling location:

Consider defect distribution: If it is known that the forging may have certain defects, such as sand holes, pores, cracks, etc., samples should be taken at and near the locations where the defects may occur in order to accurately detect the nature and degree of the defects. At the same time, samples should also be taken from defect free areas for comparison
According to the processing technology, the sampling location may vary for forgings that have undergone different processing techniques. For example, in order to study the distribution of metal flow lines in forgings that have undergone forging deformation, samples should be taken at specific locations related to the forging direction, such as cross-sections parallel or perpendicular to the forging direction; For forgings that have undergone heat treatment, it is necessary to consider the effect of heat treatment on the microstructure and properties. Samples should be taken at different locations such as the surface and core to comprehensively evaluate the heat treatment effect.
Refer to product usage requirements: Select key parts for sampling based on the stress situation and importance of the forging in actual use. For example, sampling and testing the mechanical properties of parts subjected to high stress can ensure the safety and reliability of forgings during use.

Sampling method:

Cutting and Sampling: Using cutting equipment such as grinding wheel cutting machines, wire cutting machines, etc., the forging matrix is cut into the desired sample shape and size. This method is applicable to forgings of various shapes and sizes, but it should be noted that the heat generated during the cutting process may affect the microstructure and properties of the specimen, so appropriate cooling measures such as water spray cooling should be taken
Drilling and sampling: Use a drill bit to drill cylindrical specimens on the forging matrix. When drilling, attention should be paid to maintaining the verticality and feed rate of the drill bit to avoid excessive stress and deformation of the sample. Drilling sampling is suitable for local inspection of the internal structure of forgings, but the size of the sample taken is relatively small and may not fully reflect the overall performance of the forging
Planing and sampling: Using a planer to plane the forging matrix and obtain a sample with a certain thickness and size. Planing and sampling can obtain larger samples, but the damage to the forging matrix is relatively large and the efficiency is low. It is generally suitable for forgings with regular shapes and larger sizes.

Sampling quantity:

According to the testing items: Different testing items have different requirements for the number of samples. For example, when conducting chemical composition analysis, it is generally only necessary to take a small amount of sample; To conduct mechanical performance tests such as tensile, impact, hardness, etc., multiple samples need to be taken according to relevant standards and requirements to ensure the accuracy and reliability of the test results.
Consider batch size: For forgings produced in bulk, the sampling quantity should be determined based on the batch size. Usually, the larger the batch size, the more samples are taken to better reflect the quality condition of the batch of forgings. Generally, samples can be taken according to a certain sampling ratio, such as 5% -10% of each batch of forgings, but the specific ratio should be determined based on product standards and customer requirements.

Sample size and shape:

Size requirements: The size of the sample should be determined according to the testing items and relevant standards. For example, the dimensions such as gauge length and diameter of the specimen subjected to tensile testing must comply with the corresponding national or industry standards; The sample for metallographic analysis is generally a cylinder with a diameter of 15-20mm and a height of 15-20mm, or a cube with a side length of 15-20mm.
Shape requirement: The shape of the sample should be easy to process, clamp, and test. Common shapes include cylindrical, rectangular, plate-shaped, etc. For some special testing projects, such as fatigue testing, it may be necessary to prepare specimens of specific shapes.

Marking, packaging, and preservation:

Marking: After sampling, the forging number, sampling location, sampling direction, and other information should be clearly marked on the sample for subsequent traceability and identification.
Packaging: Pack the sample with appropriate packaging materials to prevent damage, contamination, or oxidation during transportation and storage. Common packaging materials include plastic bags, paper boxes, rust proof paper, etc.
Storage: The samples should be stored in a dry, ventilated, and non corrosive gas environment, and classified according to the testing items and time requirements. For some samples that require long-term preservation, such as metallographic samples, moisture-proof and rust proof measures should be taken to ensure that the quality and performance of the samples are not affected.

Fine Processing

Precision machining:Use high-precision lathes to perform precision machining on the outer circle, end face, inner hole, and other parts of forgings to ensure dimensional accuracy and surface roughness meet design requirements. During precision machining, appropriate cutting parameters and tools should be used to achieve good machining quality

Precision milling processing:For forgings with complex shapes, such as gears, molds, etc., CNC milling machines or machining centers are used for precision milling to ensure shape accuracy and dimensional accuracy. Precision milling can use high-speed cutting technology to improve machining efficiency and surface quality.

Grinding processing:For forgings that require high surface roughness and dimensional accuracy, such as shafts and sleeves, grinding is used for final precision machining. Grinding processing can remove a small amount of excess, improve the surface quality and dimensional accuracy of forgings, and meet design requirements

Honing processing:For forgings with extremely high surface quality requirements for inner holes, such as engine cylinder blocks, hydraulic components, etc., honing can be used for ultra precision machining. Honing can further improve the dimensional accuracy, shape accuracy, and surface roughness of the inner hole, achieving a mirror effect.

Non-Destructive Testing

1、 What is non-destructive testing:

Non destructive testing (NDT) refers to the method of inspecting and testing the structure, state, type, quantity, shape, properties, position, size, distribution, and changes of defects inside and on the surface of a specimen through physical or chemical methods, with the help of modern technology and equipment, without damaging or affecting the performance of the tested object, using changes in thermal, acoustic, optical, electrical, magnetic, and other reactions caused by internal structural abnormalities or defects in the material.

2、 The non-destructive testing techniques commonly used in our company include:

1. Visual Inspection (VT):

Visual inspection is the act of collecting visual data on the state of materials. Visual inspection is the most fundamental method of examining materials or objects without altering them. Mainly includes:
Dimensional measurement: By using high-precision industrial cameras to capture flanges from different angles, and utilizing visual algorithms to accurately measure key dimensions such as outer diameter, inner diameter, thickness, bolt hole spacing, and aperture, the accuracy can reach millimeter or even micrometer level, far exceeding manual measurement, and can quickly screen out products with dimensional deviations exceeding the standard.
Surface defect detection: capable of keenly capturing scratches, sand holes, pores, cracks, rust and other defects on the flange surface. For example, fine scratches may have grayscale differences between the imaged image and the intact area under a specific light source, and the system can accurately locate them based on this; For internal sand holes, an X-ray vision inspection system is used to penetrate the flange and identify the shadow areas in the imaging.
Shape detection: Determine whether the overall shape of the flange is regular, such as checking the roundness of circular flanges and checking the geometric parameters such as straightness and perpendicularity of each side of square flanges to ensure that the product meets the design standards.
Bolt hole inspection: Carefully check the quantity, positional accuracy, and thread condition of bolt holes. Once the position deviation of the bolt hole is too large, it will be difficult to smoothly screw in the bolt during subsequent assembly. Visual inspection can avoid such problems in advance.

2. Ultrasonic testing (UT):

Ultrasonic non-destructive testing is the process of transmitting high-frequency sound waves into materials to identify changes in material properties. Ultrasonic testing uses sound waves to detect defects or imperfections on the surface of materials. One of the most common ultrasonic testing methods is pulse echo. Using this technology, inspectors introduce sound into the material and measure it when the echo (or sound reflection) generated by surface defects on the material returns to the receiver.

3. Radiographic testing (RT):

Radiographic testing involves the radiation of radioactive isotopes or X-ray generators passing through the tested material and shining onto film or other types of detectors. The readings from the detector create a shadow map that reveals potential aspects of the material being inspected. Radiographic testing can reveal aspects of materials that are difficult to detect with the naked eye, such as changes in their density.

4. Magnetic Particle Testing (MT):

Magnetic particle non-destructive testing is the behavior of identifying material defects by examining the interruption of magnetic field flow inside the material. To use magnetic particle testing, the testing personnel first induce a magnetic field in materials that are susceptible to magnetization. After inducing a magnetic field, the surface of the material will be covered by iron particles, indicating the interruption of magnetic field flow. These interruptions create visual indicators for the location of internal defects in the material.

5. Dye penetration test (PT):

Dye penetrant non-destructive testing (also known as liquid penetrant testing) refers to the process of using liquid coating materials and then searching for cracks in the liquid to identify defects in the material. The inspector conducting penetrant testing will first coat the tested material with a solution containing visible or fluorescent dyes. Then, the inspector will remove any excess solution from the surface of the material while leaving the solution in the defects that "destroy" the surface of the material. Afterwards, the inspector used a developer to extract the solution from the defect and then displayed the defect using ultraviolet light (for fluorescent dyes). For conventional dyes, the color is displayed in the contrast between the penetrant and the developer.

Surface Treatment

Typing:Perform laser coding, computer typing, or conventional typewriter engraving on products according to customer order technical document requirements or standards.

clean:Clean and dry the surface stains, impurities, iron filings, etc. of the product to lay the foundation for surface treatment.

Surface treatment:Based on decades of experience serving customers in the factory, conventional surface treatments can be divided into rust proof oil, galvanizing, painting (yellow paint, glossy black paint, matte black paint, blue paint), spray coating, etc; Surface treatment according to customer requirements.

Packaging & Shipping

packing:Pack the products that have passed the inspection using appropriate packaging materials and methods, such as plywood wooden boxes, pallets, etc., to protect the products and prevent damage during long-distance transportation and storage.

Identification mark:The product name, specifications, quantity, material, contract number and other information should be indicated on the outer packaging for easy identification and traceability.

Shipping:Ship to the port or designated location according to the customer's order requirements.