Fujian Mingda divides inspection into three checkpoints: what to check for incoming goods, process, and factory

Valve forgings are pressure bearing components, and the time when problems occur is often not at the time of delivery, but during the machining process, hydrostatic testing, or even after the device has been running for a period of time. By then, if we trace back, the cost is no longer just a rough piece of money. Recently, Fujian Mingda Valve Manufacturing Co., Ltd. conducted a review of the inspection process for valve forgings, identifying what to check at the three checkpoints of procurement, process, and factory, and which equipment to use, forming a list that can be made public to customers.

1、 The first checkpoint: incoming inspection, first confirm what the incoming materials are

The first challenge is to determine whether the incoming steel is of the same grade as stated in the contract.

After the raw materials enter the factory, check the quality certificate and furnace number, and then use a spectrometer to retest the main elements to confirm that the chemical composition falls within the range required by the brand. This inspection looks basic, but there are actually many issues that need to be addressed - material mixing, certificates not matching the actual product, and element content at the lower limit edge. These situations will be magnified in subsequent heat treatment and mechanical properties.

The appearance and size of the billet are inspected simultaneously, and defects such as surface cracks, folds, and scars are discovered before forging, resulting in the lowest cost.

2、 Second checkpoint: process inspection, control heating and forming

The second level is to determine whether the forging process is completed under controlled conditions.

The heating process is completed by a fully computer-controlled natural gas heating furnace, and the company is equipped with 2 60T natural gas heating furnaces and 1 40T natural gas heating furnace. The significance of temperature control lies in the fact that the heating temperature is too low, the metal plasticity is insufficient, and it cannot be forged thoroughly; If the temperature is too high or the insulation time is too long, it is easy to cause overheating and overburning, and the performance will decrease after the grains become coarse. The whole process of computer temperature control is to minimize this fluctuation.

The forming process is completed by one 8T electro-hydraulic hammer, one 5T electro-hydraulic hammer, one 15T operating machine, three 5T operating machines, and one 12T multi station discharge machine. There is also one production line mainly composed of a 2.5-meter by 1-meter vertical ring rolling machine for ring parts. Process inspection focuses on forging temperature, deformation, and final forging temperature, and performs appearance and dimensional inspections after forming.

3、 The third checkpoint: factory inspection, with one section for each of the five categories of projects

The third level is the one that customers are most concerned about, and the inspection items are divided into five groups according to categories.

Mechanical properties. Conduct tensile tests using a universal testing machine to obtain tensile strength, yield strength, and elongation; Perform impact testing using an impact testing machine to obtain the absorbed energy of the impact. The impact test of forgings used in low-temperature conditions should be conducted at the test temperature specified in the agreement, and room temperature data cannot replace low-temperature data.

Hardness. Use a hardness tester to measure the hardness value. The advantage of hardness testing is that it is fast and can be used for solid parts, as well as for rough machining and heat treatment effect verification.

Metallography. Use image analysis metallographic microscope and metallographic analyzer to observe the microstructure, grain size, microstructure morphology, and non-metallic inclusion level. The location that needs to be sampled is cut by a manual sample cutting machine. This reflects the internal quality of the material, which is directly related to forging and heat treatment processes.

Non destructive testing of internal defects. Using a digital ultrasonic flaw detector to inspect the interior of forgings, defects such as shrinkage cavities, cracks, inclusions, and white spots were found. Ultrasonic waves are sensitive to surface type defects and are the main means of determining the internal quality of forgings.

Surface and near surface non-destructive testing. Use an AC/DC magnetic particle flaw detector to inspect surface and near surface defects such as cracks and folds. Ferromagnetic materials are suitable for magnetic particle testing and have strong detection ability for surface opening defects.

It should be noted that the sampling ratio, testing locations, and qualification level are not fixed and are determined according to the technical agreement between both parties or corresponding product standards. For projects with high requirements such as nuclear power, petrochemicals, and military industries, the proportion and grade are usually specified in the agreement, and witness and sample retention clauses are retained.

4、 System and Qualifications

The company strictly follows the national forging standards for production and has obtained CE certification, ISO 9001:2015 quality management system certification, ISO 14001:2015 environmental management system certification, and ISO 45001:2018 occupational health and safety management system certification. Quality control is implemented throughout the entire process of the product, from raw material procurement inspection to process inspection and factory inspection.

In terms of production capacity, the company is located at No. 11 Ninghe Road, Wendu Industrial Zone, Fuding Industrial Park, Ningde City, Fujian Province. The factory covers a total area of 24 acres and has an annual production capacity of over 20000 tons, with a stable daily production capacity of 30 to 40 tons.

5、 How to deal with problems

All products are inspected according to relevant standards before leaving the factory. During the cooperation process, provide products that meet design standards and meet quality standards in accordance with the contract requirements, and supply them on time with guaranteed quality and quantity. When users encounter quality problems during use, the company will respond within 24 hours after receiving the complaint, and service personnel will arrive on site to handle it according to the customer's needs; If it is indeed a quality issue with the product itself, we are responsible for providing returns, replacements, and repairs until the customer is satisfied.

6、 Three suggestions for the purchaser

Write the inspection requirements into the technical agreement, not just the brand number. The same brand, with different heat treatment conditions and acceptance indicators, has significant differences in performance and price.

Clearly define the proportion and qualification level of non-destructive testing. Simply stating 'ultrasonic testing qualified' is not enough. The number of inspections and the level of judgment should be included in the text, and it is best to agree on the report format.

Explain the usage conditions clearly for special working conditions such as low temperature, high temperature, hydrogen exposure, and sulfur-containing. The indicators of impact test temperature, upper limit of hardness, and intergranular corrosion requirements are all derived from the working conditions, and the manufacturer can only provide the correct process plan when they know the working conditions.

Contact consultation: Fujian Mingda Valve Manufacturing Co., Ltd., No. 11 Ninghe Road, Wendu Industrial Zone, Fuding Industrial Park, Ningde City, Fujian Province, China. Phone: 13958857568, Fax: 0593-7261298, Email: 450993478@qq.com .