Partners save 15% on every standard

Valid

GB/T 47569-2026Technical specification for steel bends (English PDF)

钢制弯管技术规范

Open the GB/T 47569-2026 preview as PDF

Preview — first pages of GB/T 47569-2026 (full document: 57 pages)

This is a limited preview

Buy now to download the full PDF (57 pages)

Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

April 30, 2026

Implementation date

November 1, 2026

Scope

GB/T 47569-2026 is the English-translated version of 钢制弯管技术规范.

GB/T 47569-2026 is the Chinese national standard covering the induction-formed or cold-bent pipe bend - the wall thinning on the outside of the bend and the ovality, the mechanical properties after the heat of forming, and the non-destructive examination of a component that carries the same pressure as the straight pipe with less wall. First edition, 19,000 words, in force since 1 November 2026. It was issued on 30 April 2026 and takes effect on 1 November 2026, as a first edition. The document is under the responsibility of the China Machinery Industry Federation. This page is published from the official record of the 2026 edition; the clause text of a standard this recent is not yet in circulation, and the figures, limits and tables it contains are those of the document itself, delivered in full with the English translation.

Document preview — GB/T 47569-2026

National Standard of the People's Republic of China

ICS: 23.040.60
Classification: J 15

Issued by: State Administration for Market Regulation; Standardization Administration of the PRC

1 Scope
2 Placement of longitudinal weld seam in bend pipe
6 Shape and basic dimensional parameters
7 Design
8 Materials
9 Manufacturing
10 Heat Treatment
11 Inspection and Testing
11.2 Dimensions and Tolerances
11.2.2 Wall thickness
11.4 Mechanical Properties
11.4.1 Mechanical property test specimens
11.4.2 Tensile Test
11.4.3 Impact Test
11.4.4 Hardness Test
11.5 Non-destructive testing
13 Surface Protection and Packaging

Foreword

The following symbols apply to this document. D. Outer diameter, in millimeters (mm); d. Inner diameter, in millimeters (mm); Dmax. The maximum outer diameter of the cross-section of the curved section, in millimeters (mm); Dmin. The minimum outer diameter of the cross-section of the curved section, in millimeters (mm); D2, D

4.Outer diameters of two adjacent crests in the curved section, in millimeters (mm); D

3.Outer diameter of the trough between two adjacent crests in the curved section, in millimeters (mm); Dn. A dimension designation related to the nominal size DN or NPS, in millimeters (mm); f. Wave spacing, in millimeters (mm); h. waviness, in millimeters (mm); L

1 Scope

2.Thickness of the outer arc sidewall, in millimeters (mm); U. Flatness of the bevel end, in millimeters (mm); Deltaa. Flatness of the bend, in millimeters (mm); alpha. Bending angle, in degrees (°); epsilon. forming strain rate,%.

5.Order details The purchaser shall provide the necessary information for procuring steel pipe bends (hereinafter referred to as "bends") in the order. The order shall include at least the following information.

---Material standards and grades;

---Nominal size (or outer diameter);

---Nominal wall thickness;

--- Bending radius;

--- Bending angle;

---Length of straight pipe section;

---Type (seamless or seamed);

---Document number;

---Additional requirements.

2 Placement of longitudinal weld seam in bend pipe

9.4 During the bending process, the steel pipe should not come into contact with corrosive media or low-melting-point metals.

9.5 When using hot bending to manufacture bent pipes, the bending process should be continuous, and the heating temperature, heating range, and cooling rate should be controlled.

9.6 When manufacturing bent pipes using cold bending forming methods, the dimensions of the steel pipe should match the mold, and there should be no gaps that could cause loosening, to avoid causing damage to the bent pipe. Any dimensional deviations or defects.

9.7 If the geometric dimensions of the bent pipe are out of tolerance after forming, the bent pipe can be cold-formed. Cold forming should be carried out before heat treatment.

9.8 Before formal production of bent pipes, the manufacturer shall conduct a bending process evaluation in accordance with the provisions of Appendix D, and mass production can only begin after the process is confirmed to be qualified.

6 Shape and basic dimensional parameters

6.1 Shape The shape of the bend is shown in Figure 1.

6.2 Basic Dimensional Parameters The outer diameter and end wall thickness of the bend should conform to the requirements of GB/T 28708.Commonly used dimensions are shown in Appendix A. The supplier and buyer can customize the dimensions according to design requirements. Please use dimensions other than those in Appendix A.

7 Design

7.1 The bend should be designed to have the same internal pressure resistance as the steel pipe of the same specification, material and wall thickness to which it is connected.

7.2 The design of bends shall be carried out according to one of the following methods.

a) Calculate the wall thickness according to GB/T 20801.1 or other relevant standards.

b) Conduct design verification tests as specified in Appendix B, and determine the wall thickness of the inner and outer arcs of the bend accordingly. If necessary, provide relevant documentation. The test reports and records are provided for verification.

8 Materials

8.1 The raw materials used to manufacture pipe bends shall have quality certificates, and their chemical composition and mechanical properties shall conform to relevant material standards or design documents. The manufacturer shall conduct chemical composition analysis on the raw materials used according to the furnace number, and the analysis method shall comply with GB/T 223 (all parts). The chemical composition shall comply with GB/T 4336, GB/T 11170, etc., and the permissible deviation shall conform to the provisions of GB/T 222.

8.2 Commonly used raw materials for pipe bending are shown in Table

1.Materials other than those in Table 1 may also be selected through negotiation between the supplier and the buyer, but the materials used should meet the following requirements. In accordance with the requirements of GB/T 20801.1 or other relevant standards, and structural steel pipes should not be used to manufacture bends.

9 Manufacturing

9.1 The hot bending or cold bending forming method for pipe bending shall be determined according to factors such as material, specifications, and bending radius. Pipe bending shall not produce harmful defects.

9.2 The wall thickness of the straight pipe before bending can be selected with reference to the values given in Appendix C.

9.3 When straight seam welded pipe is used to manufacture bent pipe, the longitudinal weld should be placed within 10° from the neutral plane, as shown in Figure 2. Figure

10 Heat Treatment

10.1 Except as specified in 10.3, 10.4, and 10.5, the bending of pipes by hot bending and cold bending shall be based on factors such as material, wall thickness, forming process, and forming strain rate. Choose the appropriate heat treatment method. Table 2 shows the commonly used heat treatment methods and hardness requirements for pipe bending.

10.3 Carbon steel bends may not require heat treatment when the following conditions are met.

a) Hot-bent pipes with a final forming temperature of 750°C~950°C and a wall thickness not exceeding 20mm;

b) The pipe is formed by cold bending of raw materials that have been heat-treated at the factory, with a cold bending strain rate of less than 5%.

10.4 Unless otherwise specified, heat treatment is not required when the strain rate of cold bending of alloy steel pipe is less than 5%.

10.5 Austenitic stainless steel bends shall be solution treated as required by the technical documents; if the technical documents do not require such treatment, heat treatment is not required.

10.6 After the bent tubes are loaded into the furnace, a furnace loading layout diagram should be drawn. After the tubes are unloaded, the integrity of the markings should be checked. If any are damaged, they should be replaced in time.

10.7 During the heat treatment of bent pipes, the heating temperature inside the heat treatment furnace should be monitored. The heat treatment furnace should be equipped with an automatic temperature recording device. Complete records are available. During heat treatment, the furnace temperature difference in the effective heating zone should be controlled within ±14°C.

10.8 After the heat treatment of the bent pipe is completed, the heat treatment record should be organized and properly kept.

11 Inspection and Testing

11.1 Appearance Quality Each bent pipe should undergo surface quality inspection and should be free of cracks, scale, delamination, burrs, oxide scale, and other surface deposits. Surface zero The depth of defects such as scars, wrinkles, dents, and scratches on the star should not exceed 5% of the nominal wall thickness and should not exceed

0.8 mm. Defects exceeding these limits will result in defects in the star. Any defects should be repaired by grinding or other methods. The repaired area should have a smooth transition, and the wall thickness of all repaired areas should not be less than the specified thickness for that part of the bend. Minimum wall thickness.

11.2 Dimensions and Tolerances

11.2.1 Pipe end dimensions The tolerances for the outer and inner diameters of the bend pipe ends shall conform to the provisions of Table 3.

11.2.2 Wall thickness

11.2.2.1 The minimum wall thickness of the pipe body for the outer and inner arcs of the bend shall comply with the provisions of 7.2.

11.2.2.2 Unless otherwise specified by the purchaser, the wall thickness at the pipe end bevel shall not be less than 87.5% of the nominal wall thickness.

11.2.3 Out-of-roundness The out-of-roundness of the same cross-section of the bent section of the pipe is shown in Figure

3.The out-of-roundness µ of the bent pipe is calculated according to formula (3), and the out-of-roundness should conform to Table 4. Regulation.

11.2.4 Bending radius and bending angle The bending radius R and bending angle alpha of the pipe bend are shown in Figure

4.The allowable deviation of the bending radius is no greater than 1%R and no greater than... ±50mm, bending angle deviation not greater than ±1°.

11.2.5 Flatness The flatness of the bend is shown in Figure

5.The flatness Deltaa of the bend should conform to the specifications in Table 5.

11.2.6 Pipe end beveling Unless otherwise specified, the ends of bent pipes shall be beveled. The shape and dimensions of the bevel are shown in Figure

6.The bevel dimensions for pipe ends with different nominal wall thicknesses shall conform to the specified requirements. According to the provisions of Table 6.

11.2.8 Flatness of the bevel end The flatness of the bevel end is shown in Figure

8.The flatness U of the bevel end should conform to the specifications in Table 8.

11.2.9 Wavyness and Wavy Spacing of Bends The surface of the bent pipe should not have obvious wrinkles. The waviness of hot-bent pipes should not exceed 2% of the outer diameter, and the waviness of cold-bent pipes should not exceed [missing value]. The outer diameter is 3%, and the wave spacing f should not be less than 12h, as shown in Figure 9.

11.3 Chemical composition Chemical composition analysis was performed on the bent pipes according to the smelting furnace number, and the analytical methods were in accordance with GB/T 223 (all parts), GB/T 4336, and GB/T The chemical composition shall comply with the chemical composition requirements of the grade specified in the standard for raw materials used in bends, as stipulated in 11170, etc.

11.4.1 Mechanical property test specimens

11.4.1.1 Mechanical property test specimens for factory inspection of bent pipes should preferably be prepared from bent pipes after heat treatment (or after forming that does not require heat treatment), or they can be taken from... Impact test specimens should be taken from the same batch of bent pipes and heat-treated in the same furnace as the manufacturing process. The impact test specimens should be taken from the thickest bent pipe or sample in the same batch.

Note. A batch is defined as one using the same raw material grade, the same smelting furnace number, similar raw material specifications (thickness difference less than or equal to 6mm), and the same forming process. Bent pipes manufactured using the same heat treatment process. The same applies below.

11.4.1.2 The mechanical property test specimens for the evaluation of the bending process shall be prepared from the finished bending pipe in accordance with the provisions of Appendix D.

11.4.1.3 The weld axis of the tensile test specimen should be located at the midpoint of the specimen's length. Both circular and strip specimens can be used for tensile testing. Yes, small circular specimens can be taken when thickness is a limitation. When the shape and wall thickness of the bent pipe prevent the preparation of the aforementioned specimens, it is unnecessary to proceed. Tensile test.

11.4.1.4 The length direction of the weld impact test specimen should be perpendicular to the length direction of the weld, the axis of the notch should be perpendicular to the weld surface, and the notch should... Located in the middle of the weld. Impact testing should preferably use a standard 10mm × 10mm specimen; when the size and shape of the bend or blank are insufficient... When preparing standard specimens, the smallest possible specimen with the greatest possible thickness should be prepared; if it is insufficient to prepare the smallest possible specimen with the greatest possible thickness, then... Impact testing is mandatory.

11.4.2 Tensile Test

11.4.2.1 The tensile test of the bend shall be conducted in accordance with the provisions of GB/T 228.1, and the tensile test results of samples taken from relevant parts of the bend shall meet the relevant requirements. Material standards or design document requirements.

11.4.2.2 During factory inspection, a tensile test should be performed on each batch of bent pipes; for welded bent pipes, a tensile test should also be performed on the weld seam of each batch of bent pipes. Tensile test; for bends that do not require heat treatment, the tensile properties of the raw material can represent the tensile properties of the bend.

11.4.2.3 During process evaluation, tensile tests shall be conducted at the sampling locations specified in Table D.2.

11.4.2.4 If the tensile test results do not meet the requirements, two more tensile specimens may be taken for retesting. The test results shall be deemed qualified if they both meet the requirements.

11.4.2.5 Except as otherwise provided above, tensile tests may be conducted in accordance with the terms agreed upon by both the supplier and the buyer.

11.4.3 Impact Test

11.4.3.1 The impact test of the bend shall be conducted in accordance with GB/T 229, and the impact test results of samples taken from relevant parts of the bend shall conform to the relevant raw material specifications. Material standards or design document requirements.

11.4.3.2 During factory inspection, each batch of pipe bends made of steel suitable for low-temperature applications shall undergo an impact test; for welded pipe bends, each batch shall also undergo an impact test. An impact test should be conducted on the weld. Whether an impact test is required for bends made of other materials can be determined through negotiation between the supplier and the buyer.

11.4.3.3 During process evaluation, impact tests shall be conducted at the sampling locations specified in Table D.2.

11.4.4 Hardness Test

11.4.4.1 The hardness test of the bent pipe shall be conducted in accordance with GB/T 17394.1 or GB/T 231.1.The hardness value shall be obtained from at least three tests. The arithmetic mean of the raw materials and that meets the requirements of Table 2 or the relevant raw material standards.

11.4.4.2 Alloy steel and low-temperature steel bends shall be subjected to hardness testing on each piece. Bends of other material categories shall be tested for hardness on a per-heat-treatment-furnace basis. For each batch (excluding those requiring heat treatment), sampling shall be conducted, with a minimum of 10% and a minimum of one piece taken from each variety and specification. Hardness test; if one piece fails, the sampling should be doubled; if one piece still fails, all pieces should be tested.

11.4.4.3 When the supplier and the buyer have any objection to the hardness test results, arbitration shall be conducted in accordance with the test method specified in GB/T 231.1.

11.5 Non-destructive testing

11.5.1 For all types of pipe bends made of various materials, magnetic particle testing shall be performed according to NB/T 47013.4 or relevant standards, depending on the suitability of the material. Penetrant testing shall be conducted in accordance with NB/T 47013.5 or relevant standards, and Level I is considered (qualified).

11.5.2 For all types of pipe bends, ultrasonic testing may be performed upon negotiation between the supplier and the buyer. The testing shall be conducted in accordance with NB/T 47013.3 or... The relevant standards will be followed, and the testing ratio and acceptance standards will be negotiated between the supplier and the buyer.

11.5.3 For bends manufactured from welded steel pipes, if the weld seam has been 100% radiographically inspected and passed by the steel pipe manufacturer, the bend... Pipe welds are not required to undergo radiographic testing, unless otherwise specified. If the pipe welds are not 100% radiographically inspected by the pipe manufacturer, then... Pipe bend manufacturers should conduct radiographic testing on the entire length of the bend weld in accordance with NB/T 47013.2 or relevant standards, with Level II being acceptable.

11.5.4 In addition to the above provisions, non-destructive testing may be carried out according to the content agreed upon by the supplier and the buyer.

11.5.5 Personnel engaged in non-destructive testing should obtain the corresponding qualifications.

11.6 Metallographic Examination Alloy steel bends should undergo metallographic examination according to GB/T 13298.They should not exhibit overheated structures, and the metallographic structure should be at least 100 times the strength of the metal... Microcracks should not be present in the phase structure photograph.

11.7 Grain size detection Each batch of high-carbon austenitic stainless steel bends should undergo a grain size test, according to the specifications in GB/T 6394.Delivery condition... The grain size of the lower bend should be grade 7 or coarser.

11.8 Ferrite Detection For each batch of austenitic-ferritic duplex stainless steel bends, a ferrite test should be performed, and the test method should comply with GB/T 13305. Or as specified in relevant standards. When using the ferrite analyzer method, ferrite testing should be performed at least three times on the outer arc side of the bending zone. Delivery condition. The ferrite content of the downward-bent pipe body should be 40% to 60%. The ferrite content in the weld area shall be negotiated between the supplier and the buyer.

11.9 Hydrostatic Test This document does not require separate hydrostatic testing for bends. All bends should be able to withstand pressure tests equivalent to those of steel pipes of the same material, diameter, and wall thickness. The water pressure test pressure required by the applicable piping specifications shall not be present, and there shall be no leakage or defects that would impair its performance.

11.10 Other Other inspection and testing items and requirements for pipe bends shall be determined through negotiation between the supplier and the buyer.

11.11 Factory Inspection and Testing Table 9 summarizes the factory inspection and testing of the bent pipes. 12 signs

12.1 Marks should be made on the outer surface of the bend, and the distance between the mark and the end of the pipe should not be less than 150mm.

12.2 The lettering of the sign should be clear and durable, and the sign should not be made by hammering or stamping lettering.

12.3 The sign shall include at least the following.

13 Surface Protection and Packaging

13.1 The outer surface of carbon steel and alloy steel bends should preferably be treated with sandblasting, shot blasting, or surface coating with anti-rust paint; the surface of stainless steel bends should be acid-treated. Washing and passivation treatment; or as required by the purchaser.

13.2 Products should be stored and packaged according to different material types, and attention should be paid to moisture prevention.

14.Product Quality Certificate A product quality certificate should be provided for the bend, and the product quality certificate should include at least the following.

a) The manufacturer's name and address;

b) Product name and type (seamless or seamed);

c) The grade, batch number, and standard number of the raw materials;

d) Nominal dimensions or outer diameter and wall thickness;

e) Bending radius, bending angle; quantity and product number;

f) This document number;

g) Chemical composition;

h) Non-destructive testing;

i) Mechanical properties;

j) Delivery status;

k) Inspection test results and other inspection test results specified in the order;

......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 57 pages — is available in the English PDF.

How to Buy GB/T 47569-2026

1Add to cart. Click the "Buy GB/T 47569-2026" button on this page. You can add more standards before checkout.
2Checkout. Enter your email and billing details. Payment is processed securely by Stripe (cards, Apple Pay, Google Pay supported).
3Instant delivery (0–9 sec). Delivery is automatic: within seconds of payment you'll receive an email with a secure download link. The link stays valid for 72 hours.
4Invoice included. A tax invoice is attached to the confirmation email. Need a custom invoice? Contact us.