Production Technical Specifications for Medium and Low Pressure Fittings

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Preface: This standard is primarily formulated with reference to the GD87 standard and other standards related to steel pipe production, taking into account the characteristics of the pipe fitting industry. This standard is being developed for the first time. This standard was proposed by the Technical Center of Hebei Beihai Pipeline Manufacturing Co., Ltd. This standard was drafted and interpreted by the Technical Department of Hebei Beihai Pipeline Manufacturing Co., Ltd. The main drafter of this standard: Gao Wentong. Table of Contents 1 General Provisions…………………………………………………………………………………………………………12 Basis for Preparation……………………………………………………………………………………………………13 Inspection Procedures for Pipes………………………………………………………………………………………………14 Inspection Requirements for Seamless Fittings…………………………………………………………………………24.1 General Provisions………………………………………………………………………………………………24.2 Specific Provisions…………………………………………………………………25 Heat Treatment of Fittings…………………………………………………………………36 Marking…………………………………………………………………………………………………………47 Storage upon Arrival…………………………………………………………………………………………………5 1 Pressed Fittings Section 1.1 Materials: 1) The materials used shall be seamless steel pipes and steel plates made of 20# steel as specified in GB3087, GB5310, and GB713, seamless steel pipes made of 12Cr1MoV steel, as well as seamless steel pipes and steel plates of other suitable steel grades, which will serve as the raw materials. 2) Steel pipes with a positive deviation and steel plates of greater thickness are used as the blanks for pipe fittings. Since the wall thickness of the pipe fittings specified in the standards corresponds to the actual wall thickness required for the finished products, the blank thickness must be determined by the company after applying an appropriate reduction based on the processing method, and the technical documents accompanying the steel materials must also be reviewed. 1. 1.2 Manufacturing 1) The inner and outer surfaces of the steel pipe must be cleaned thoroughly, and inspections of both the inner and outer surfaces shall be carried out after cleaning ； 2) The inner and outer surfaces of the steel pipe must be free from defects such as cracks, scars, tears, delamination, and folds. Such defects must be completely removed, and removing them must not result in a wall thickness reduction exceeding the specified tolerance values ； 3) The steel pipe can be spun on a machine tool or cut into tube blanks using an oxy-acetylene flame, and all burrs and uneven edges must be removed by mechanical means ； 4) Tube billet heating method and heating temperature: 4.1) For 12Cr1MoV steel, the upper heating limit is 1050–1100, with the final rolling temperature above 850 ； 4.2) For 20# steel, the upper heating temperature is 1050–1100, with the final cooling temperature above 800 ； 4.3) Other steel grades shall be processed at their specified hot working temperatures and final rolling temperatures ； 4.4) For alloy steel grades, if the final rolling temperature is used in place of normalizing, this temperature is determined by the company based on the characteristics of the steel grade. 5) The heat treatment procedures for pipe fittings are as follows:
For steel grades:
20#: Normalizing at 870–900°C for 15 minutes.
10CrMo9: Quenching at 900–960°C, followed by air cooling or oil cooling; then tempering at 700–750°C with air cooling.
12Cr1MoV: If δ ≤ 40, normalizing at 1000–1020°C for 30 minutes followed by air cooling; tempering at 720–760°C with a holding time of 3 hours. If δ > 40, normalizing at 1000–1020°C for 30 minutes, followed by oil cooling or forced air cooling; tempering at 720–760°C with a holding time of 3 hours. The holding time for normalizing is determined at 1 minute per mm, while the holding time for tempering is determined at 2 minutes per mm. For other steel grades, our company can decide on the appropriate procedures based on specific conditions. 6) Our company measures the wall thickness reduction for the fittings of each parameter, and conducts random pressure tests on batches of fittings. 2. Dimensions and tolerances: Strictly comply with the requirements of GD87 standard ； 3. Inspection and acceptance: 1) Our company’s quality control department conducts inspections in the following order: a. Check the quality of raw materials based on the purchasing conditions ； b. Check the external dimensions ； c. Use an ultrasonic thickness gauge to measure the wall thickness of the high-pressure pipe fittings and keep a record of it ； d. Perform non-destructive testing on the high-pressure fittings to determine whether there are any cracks or other defects, and measure the hardness value after heat treatment ； e. Check the markings and paint on the pipe fittings, etc. 2) After each fitting is inspected, a stamp from the quality control department indicating that the inspection is complete is applied to it ； 3) The data and inspection results related to the pipe fittings are included in the factory technical documents. 4. Packaging markings and documents: 1) Pipe fittings should be painted or coated with grease to prevent rusting during storage and transportation ； 2) Mark the label at the designated position of each fitting ； 3) The pipe fittings are supplied with factory technical documents in a format specified by the company at the time of shipment. 1.2 Forged Fittings – Section 1: Materials: 1) The materials used are 20# steel produced by electric furnaces, open-hearth furnaces, or pure oxygen top-blown converters, high-quality deoxidized steel such as 12Cr1MoV, or ingots and bars of the same steel grade; other steel grades that meet the required specifications may also be used. 2) The steel ingots or steel materials used must come with certification documents; those without such documents must undergo additional testing before they can be used ； Random inspections are conducted on those with certificates of conformity. The inspection items include: a. Grain size of the material: 4–8 grade for 20# steel, 4–5 grade for 12Cr1MoV steel ； b. The macrostructure and internal defects of the steel, as shown in the grading diagrams, shall be within the following categories: central porosity: grade 2 ； General looseness: Grade 2 ； Segregation: Grade 2 ； White spots: Level 0 ； Stomata: Grade 2, stomatal depth not exceeding 2 mm ； c. The purity of non-metallic inclusions shall not exceed the following categories: Oxides: Grade 4 ； Sulfides: Grade 4 ； 3) The chemical composition of the material shall meet the following standards: 20# steel: GB699 ； 12Cr1MoV steel: GB222 ； When other steel materials are used, relevant regulations shall be complied with ； 2. Manufacturing 1) Before manufacturing, remove the defective parts (upper and lower sections) from the steel ingots (rods); it is necessary to ensure that there are no visually visible defects such as shrinkages, pores, porosity, cracks, or non-metallic inclusions at the ends ； 2) When manufactured directly from ingots, the forging ratio (the ratio of the cross-sectional area before to that after forging), calculated based on the main cross-section or based on the flanges or other protruding parts, shall be not less than 1.5 ； 3) Control the heating, cooling, initial forging, and final forging temperatures of the forging blank to ensure excellent quality of the forging and minimal internal stresses, while preventing localized heating of the forging to the forging temperature without actual forging taking place ； 4) There should be no sharp corners at the joints of the forged parts ； 5) The surface of the forged part shall be free of local defects such as cracks, laminations, folds, forging defects, scars, and inclusions. When such local defects are found, they shall be removed by grinding, and the depth of grinding shall comply with the following requirements: a) On surfaces that do not require machining, the depth of removal shall not exceed the negative tolerance of the dimensions of that part ； b. On the surfaces that require machining, it shall not exceed 75% of the unilateral machining allowance at that location ； 6) No white spots, nor any visibly visible cracks, non-metallic inclusions, or other defects should be present in any part of the forgings. The inspection for white spots shall be carried out in accordance with the process documents or the technical requirements specified in the order; if white spots are found in a batch of forgings, each forging in that batch must be inspected individually ； 7) The heat treatment procedures for pipe fittings are as follows: For steel grades, the heat treatment procedures are as follows – For 20#: normalizing at 900~930°C for 15 minutes; for 12Cr1MoV: if δ ≤ 40, normalizing at 1000~1020°C followed by tempering at 720~760°C (with a holding time of 3 hours); if δ > 40, normalizing at 1000~1020°C followed by oil cooling or forced air cooling, then tempering at 720~760°C (with a holding time of 3 hours). The holding time during normalizing is determined based on 1 minute per mm, but it must not be less than 30 minutes. Note: When it is possible to control the final forging temperature at 900°C or above, 20# steel forgings can be delivered in their final forged state, while 12Cr1MoV steel forgings can be delivered in their final forged state after tempering (at the same tempering temperature). However, the properties of the forgings must meet all the requirements specified in the technical specifications.