Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces TB/T 3012-2006 Specification of Cast Steel Bolster and Side Frame for Railway Freight Car. The following main technical changes have been made with respect to TB/T 3012-2006:
——The chemical composition and mechanical properties requirements of Grade B+ steel are added (see 3.2 and 3.3);
——The requirements for mechanical property of physical product are added (see 3.3.2);
——The requirements for the smelting process of electric arc furnace and refining furnace are added (see 3.5.1);
——The process requirements for residual aluminum and steel reducing slag (FeO) of steel are added (see 3.5.2);
——The process requirements for the killing of molten steel after tapping are added (see 3.5.3):
——The requirements for the automatic integral core setting process for bogie bolster and side frame with axle weight of 25t and above as well as the continuous heat treatment process of bogie bolster and side frame with axle weight of more than 25t are added (see 3.5.4):
——The requirements for heat treatment process of Grades B and B+ steels are modified (see 3.5.5; 3.5.3 of Edition 2006);
——The process requirement for shake-out and cleaning of castings are added (see 3.5.6);
——The process requirements for cleaning of castings after heat treatment are modified (see 3.5.7; 3.5.5, Edition 2006):
——The requirements for visual inspection are modified (see 3.6.1; 3.6.2, Edition 2006);
——The requirements for magnetic particle testing are modified (see 3.6.9; 3.10.1, Edition 2006);
——The requirements for compactness inspection are modified (see 3.7.1; 3.11, Edition 2006);
——The requirements for radiographic testing are modified (see 3.7.2; 3.10.2, Edition 2006);
——The requirements as to the preparation of the groove for repair welding after heat treatment are modified (see 3.8.3; 3.7.4, Edition 2006);
——The requirements for the welding environment are added (see 3.8.5);
——The processing method in case of casting temperature lower than 4°C and the requirements for repair welding of Grade C steel are added (see 3.8.6);
——The requirements for the quality of repair welding are modified (see 3.8.10; 3.7.8, Edition 2006);
——The requirements for the recommended temperature for repair welding and tempering of bolsters and side frames after heat treatment are added (see 3.9.1);
——The requirements for the repair welding of Parts A and B of bolster after heat treatment are modified (see 3.9.1.1; 3.8.1.1, Edition 2006):
——The requirements for the post heating repair welding treatment of the area 50mm around the bolster lever hole are modified (see 3.9.2.2; 3.8.1.2, Edition 2006);
——The requirements for repair welding of Part A of side frame after heat treatment are modified (see 3.9.3.1; 3.8.2.1, Edition 2006);
——The requirements for post-heating repair welding treatment of Part B on side frame are modified (see 3.9.3.2; 3.8.2.2, Edition 2006):
——The requirements for the post-heating repair welding treatment are added for the connection corner between the post of side frame central frame and the spring cushion cap as well as the area (R+45)mm around the corner (see 3.9.3.2; 3.8.2.3, Edition 2006);
——The requirements for static load and fatigue tests are modified (see 3.11; 3.12, Edition 2006);
——The requirements for specimen preparation are added (see 4.1);
——The methods for surface roughness inspection are added (see 4.5.1);
——The methods for internal quality inspection are added (see 4.6);
——The inspection method for geometric dimension of castings are added (see 4.7);
——The rules for type inspection, periodic inspection and end-of-manufacturing inspection are added (see 5.1, 5.2 and 5.3);
——The rules for mechanical property inspection of bolster and side frame in case of insufficient test rods are deleted (see 4.2.8, Edition 2006);
——The requirements for marking are modified (see 6.1; 5.1, Edition 2006);
——The requirements for quality certificate are modified (see 6.2; 5.2, Edition 2006);
——The division methods for Parts A and B of ZK7 bolster and side frame are added (see Annex A);
——The metallographic atlas for metallographic microstructure examination of Grade B cast steel (ZG25MnNi) and Grade C cast steel (ZG25MnCrNiMo) are deleted (see Annexes A and B, Edition 2006);
——The requirements for qualified level of Parts A and B of bolster and side frame upon radiographic testing are added (See Annex C);
——The schematic diagrams are added as to dissected part for compactness inspection of ZK7 bolster and side frame (see Annex E);
——The position requirements are added as to the thickness measurement points for important parts of the bolster and side frame are added (see Annex F).
This standard was proposed by and is under the jurisdiction of CRRC Qishuyan Locomotive & Rolling Stock Technology Research Institute Co., Ltd.
Previous editions of this standard are as follow: TB/T 3012-2001 and TB/T 3012-2006.
Cast Steel Bolster and Side Frame for Railway Freight Car
1 Scope
This standard specifies technical requirements, inspection methods, inspection rules, marking and quality certificate and records for Grade B steel (ZG25MnNi), Grade B+ steel (ZG25MnCrNi) and Grade C steel (ZG25MnCrNiMo) bolsters and side frames for railway freight car.
This standard is applicable to the manufacture and inspection of Grades B, B+ and C steel bolster and side frame for railway freight car.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 222 Permissible Tolerances for Chemical Composition of Steel Products
GB/T 223 Methods for Chemical Analysis of Iron, Steel and Alloy
GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature (GB/T 228.1-2010, ISO 6892-1: 2009 MOD)
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method (GB/T 229-2007, ISO 148-1: 2006, MOD)
GB/T 6394 Metal-methods for Estimating the Average Grain Size
GB/T 6414-1999 Castings - System of Dimensional Tolerances and Machining Allowances (eqv ISO 8062: 1994)
GB/T 15056 Evaluation Method on Cast Surface Roughness
JB/T 5105 Casting Form Pattern Draft
TB/T 1959 Static Load and Fatigue Test of Bolster and Side Frame for Railway Freight Car
TB/T 2451 Metallographic Inspection for Non-metallic Inclusion in Cast Steel
TB/T 2942 General Technical Specifications of Steel Castings for Rolling Stock
TB/T 3105.1 Nondestructive Testing of Cast Steel Bolster and Side Frame for Railway Freight Car - Part 1: Radiographic Testing
TB/T 3105.3 Nondestructive Testing of Cast Steel Bolsters and Side Frames for Railway Freight Car - Part 3: Magnetic Particle Testing
TB/T 3105.4-2014 Nondestructive Testing of Cast Steel Bolsters and Side Frames for Railway Freight Car - Part 4: Digital Radiography and Industrial Computed Tomography Testing
TB/T 3211 Imperfections of Radiographic Testing for Steel Castings for Rolling Stock
TB/T 3212.1 Metallographic Atlas for Metallographic Microstructure Examination of Low Alloy Cast Steel for Rolling Stock - Part 1: Grades B and B+ Cast Steel
TB/T 3212.2 Metallographic Atlas for Metallographic Microstructure Examination of Low Alloy Cast Steel for Rolling Stock - Part 2: Grades C Cast Steel
3 Technical Requirements
3.1 General requirements
3.1.1 The bolster and side frame shall be in accordance with this standard as well as those specified in the technical documents and product drawings approved via established procedures.
3.1.2 The two important parts, i.e., A and B, shall be determined according to the stress state of the bolster and side frame and then specified in the product drawing. See Annex A for the division of Parts A and B of bolster and side frame.
3.2 Chemical composition
The chemical composition of the steel shall be in accordance with those specified in Table 1.
Table 1 Chemical Composition
Grade Chemical composition (mass fraction)
%
C≤ Si≤ Mn≤ P≤ S≤ Cu≤ Ni≥ Cr≤ Mo≤
Grade B 0.28 0.40 1.00 0.030 0.030 0.30 0.30 — —
Grade B+ 0.29 0.50 1.00 0.030 0.030 0.30 0.20 0.50 —
Grade C 0.28 0.40 1.50 0.030 0.030 0.30 0.35 0.60 0.30
For Grades B and B+ steels, if the carbon content is lower than the maximum value specified, the manganese content is allowed to be 0.04% higher than the specified maximum value each time the carbon content is reduced by 0.01%, but the maximum manganese content shall not be greater than 1.20%.
3.3 Mechanical property
3.3.1 The mechanical property of steel test rod shall be in accordance with the relevant requirements of TB/T 2942.
3.3.2 Where the products are randomly inspected or it is required by the customer, the mechanical property of cast steel may be evaluated with a physical specimen of which the mechanical properties shall be in accordance with the relevant requirements of TB/T 2942.
3.4 Metallographic phase
The metallographic analysis of cast steel covers the evaluation of nonmetallic inclusion, grain size and metallographic structure. Non-metallic inclusions shall be evaluated according to TB/T 2451 and shall be in accordance with those specified in Table 2; the grain size of the product shall be evaluated according to GB/T 6394, and the conformity level shall be stricter than or equal to Grade 6; the metallographic structure of Grade B and B+ steels shall be evaluated in accordance with TB/T 3212.1, and that of Grade C steel shall be evaluated in accordance with TB/T 3212.2.
Table 2 Rating of Non-metallic Inclusions in Cast Steel
Inclusion classification Conformity level Rating chart
Type I (globular) inclusion Thin: Grades 1~3; thick: Grade 1 Third rating chart
Type II (point-net) inclusion Grade 1~Grade 2 Second rating chart
Type III (dotted) inclusion Thin: Grades 1~3; thick: Grades 1 Third rating chart
Type IV (aluminum oxide cluster) inclusion Grade 1 Fourth rating chart
3.5 Process requirements
3.5.1 The cast steel shall be smelted with electric arc furnace and refining furnace.
3.5.2 The residual aluminum in the steel shall be controlled within 0.020%~0.080%. The reducing slag (FeO) in at least one melting furnace shall be taken every week to measure the reducing slag (FeO) content which shall not be greater than 1.0%; the keel block of the steel in at least one furnace No. shall be taken to inspect the oxygen content of the steel, which shall not be greater than 0.0060%.The residual aluminum, reducing slag (FeO) and oxygen content in steel will not be used as the basis for product delivery.
3.5.3 After tapping (in the pouring pot), the molten steel shall be killed for at least 5min and the pouring temperature shall not exceed 1,585°C.
3.5.4 Automatic integral core setting process shall be adopted for bogie bolsters and side frames with axle weights of 25t and above. Continuous heat treating furnace process shall be adopted for bogie bolsters and side frames with axle weights of 25t and above.
3.5.5 The bolster and side frame shall be subjected to heat treatment. Bolster and side frame made of Grades B and B+ steels shall be subjected to normalizing or normalizing & tempering heat treatment, and those made of Grade C steel shall be subjected to normalizing and tempering heat treatment. Where re-heat treatment is necessary, the frequency of re-heat treatment shall not exceed two times (the frequency of tempering is unlimited).The heat treatment of bolster and side frame shall be in accordance with the relevant requirements of TB/T 2942.
3.5.6 Dry knockout shall be adopted for bolster and side frame. During shake-out, the temperature of the casting shall not be higher than 540°C, the method of sand removal and its cooling rate shall not impair the quality of the casting.
3.5.7 After final heat treatment, the bolster and side frame shall not be cleaned via thermal method.
3.5.8 The temperature for correcting the distorted bolster and side frame shall not exceed 850°C; the castings corrected after heat treatment shall be heat treated and inspected again.
3.6 Surface quality
3.6.1 The surface of bolster and side frame shall be free of cracks via visual inspection; and the sand burning that impedes use and inspection shall be removed.
3.6.2 Unless it is otherwise specified in the product drawing and technical documents, the surface roughness of castings shall be NMR Ra100.
3.6.3 As for the castings, the flying edge and burrs presenting on the outer edge and the edges of the holes shall be totally removed and the edges shall be rounded; the conspicuous raised surface on the casting shall be polished flat and smooth.
3.6.4 The residual casting head on non-machined surface shall not exceed 3mm and it shall be smoothly transitioned to the surrounding casting surface.
3.6.5 Parts A and B of the bolster and side frame shall be free from visible chipping marks or nicks; the depth of those chipping marks and nicks on other parts shall not be greater than 2mm;chipping marks and nicks produced during manufacturing are allowed to be removed by grinding and shall be smoothly transitioned to the surround part, but the wall thickness at the ground part shall not be less than the minimum allowable size.
3.6.6 The non-machined casting surface within a radius of 25mm around the center of bolt (rivet) hole shall be flat and smooth.
3.6.7 The following defects are allowed to be left on the bolster without repair:
a) Local dent with a casting wall thickness no less than the minimum allowable value specified in the drawing and a depth less than or equal to 2mm after cleaning, which shall be so finished as to transition smoothly to the surrounding casting surface;
b) Local protrusions which are less than or equal to 2mm in height and have no influence on processing and assembly;
c) Gas holes scattered on the bolster surface (excluding Part A), which are less than or equal to 2mm, 5mm and 3pcs/cm2 in diameter, depth and density.
3.6.8 The following defects are allowed to be left on the side frames without repair:
a) Local dents spaced less than 100mm on Part A, of which the casting wall thickness is no less than the minimum allowable value specified in the drawing, the depth is less than or equal to 2mm, and the maximum dimension is less than or equal to 10mm after cleaning; such dents shall be so finished as to transition smoothly to the surrounding casting surface;
b) Local dent presenting on other parts with a casting wall thickness no less than the minimum allowable value specified in the drawing and a depth less than or equal to 3mm after cleaning, which shall be so finished as to transition smoothly to the surrounding casting surface;
c) Local protrusions which are less than or equal to 2mm in height and have no influence on processing and assembly;
d) Gas holes scattered on the side frame surface (excluding Part A), which are less than or equal to 2mm, 5mm and 3pcs/cm2 in diameter, depth and density respectively.
3.6.9 The magnetic particle testing of the surface shall be in accordance with the following requirements:
a) magnetic particle testing shall be performed on Parts A and B of the bolsters and side frames as well as other parts required to be tested in the drawing. The parts to be tested shall be free of cracks or transverse linear magnetic trace of defects;
b) for the bolster, the length of magnetic particle indication for a single longitudinal linear defect is allowed to be no larger than 5mm; the accumulative length of magnetic particle indication for dispersed defects with length greater than or equal to 3mm and less than 5mm is allowed to be no larger than 30mm within a rectangular area (with the long side no larger than 150mm) of 2,500mm2;
c) for the side frame, the length of magnetic particle indication for a single longitudinal linear defect is allowed to be no larger than 5mm; the accumulative length of magnetic particle indication for dispersed defects with length greater than or equal to 3mm and less than 5mm is allowed to be no larger than 24mm within a rectangular area (with the long side no larger than 150mm) of 2,500mm2;
3.6.10 In case of any of the following defects, the bolster shall be discarded:
a) transverse penetrating cracks on Parts A and B;
b) other penetrating casting defects presenting on Parts A and B with a single area exceeding 30 cm2 or a total area exceeding 60 cm2.
3.6.11 In case of any of the following defects, the side frame shall be discarded:
a) transverse penetrating cracks on Parts A and B;
b) the following defects presenting on Part A: other penetrating cracks with a length exceeding 50mm; or a single penetrating defect of other type with the area exceeding 20cm2, or more than one penetrating defects of other type with the area exceeding 20cm2;
c) the following defects presenting on Part B: other penetrating cracks with a length exceeding 50mm; or a single penetrating defect of other type with the area exceeding 25cm2, or more than one penetrating defects of other type with the area exceeding 50cm2;
Foreword i
1 Scope
2 Normative References
3 Technical Requirements
4 Inspection Method
5 Inspection Rules
6 Marking and Quality Certificate
7 Record
Annex A (Normative) Partitioning Methods for Part A and Part B of Bolsters and Side Frames
Annex B (Normative) Bolster and Side Frame Compactness Standard Picture
Annex C (Normative) Radiography Qualification Grades for Part A and Part B of Bolster and Side Frame
Annex D (Normative) Measuring Basis of Bolster and Side Frame
Annex E (Normative) Bolster and Side Frame Compactness Inspection and Dissection Positions
Annex F (Normative) Location of Thickness Measuring Points for Important Parts of Bolster and Side Frame
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces TB/T 3012-2006 Specification of Cast Steel Bolster and Side Frame for Railway Freight Car. The following main technical changes have been made with respect to TB/T 3012-2006:
——The chemical composition and mechanical properties requirements of Grade B+ steel are added (see 3.2 and 3.3);
——The requirements for mechanical property of physical product are added (see 3.3.2);
——The requirements for the smelting process of electric arc furnace and refining furnace are added (see 3.5.1);
——The process requirements for residual aluminum and steel reducing slag (FeO) of steel are added (see 3.5.2);
——The process requirements for the killing of molten steel after tapping are added (see 3.5.3):
——The requirements for the automatic integral core setting process for bogie bolster and side frame with axle weight of 25t and above as well as the continuous heat treatment process of bogie bolster and side frame with axle weight of more than 25t are added (see 3.5.4):
——The requirements for heat treatment process of Grades B and B+ steels are modified (see 3.5.5; 3.5.3 of Edition 2006);
——The process requirement for shake-out and cleaning of castings are added (see 3.5.6);
——The process requirements for cleaning of castings after heat treatment are modified (see 3.5.7; 3.5.5, Edition 2006):
——The requirements for visual inspection are modified (see 3.6.1; 3.6.2, Edition 2006);
——The requirements for magnetic particle testing are modified (see 3.6.9; 3.10.1, Edition 2006);
——The requirements for compactness inspection are modified (see 3.7.1; 3.11, Edition 2006);
——The requirements for radiographic testing are modified (see 3.7.2; 3.10.2, Edition 2006);
——The requirements as to the preparation of the groove for repair welding after heat treatment are modified (see 3.8.3; 3.7.4, Edition 2006);
——The requirements for the welding environment are added (see 3.8.5);
——The processing method in case of casting temperature lower than 4°C and the requirements for repair welding of Grade C steel are added (see 3.8.6);
——The requirements for the quality of repair welding are modified (see 3.8.10; 3.7.8, Edition 2006);
——The requirements for the recommended temperature for repair welding and tempering of bolsters and side frames after heat treatment are added (see 3.9.1);
——The requirements for the repair welding of Parts A and B of bolster after heat treatment are modified (see 3.9.1.1; 3.8.1.1, Edition 2006):
——The requirements for the post heating repair welding treatment of the area 50mm around the bolster lever hole are modified (see 3.9.2.2; 3.8.1.2, Edition 2006);
——The requirements for repair welding of Part A of side frame after heat treatment are modified (see 3.9.3.1; 3.8.2.1, Edition 2006);
——The requirements for post-heating repair welding treatment of Part B on side frame are modified (see 3.9.3.2; 3.8.2.2, Edition 2006):
——The requirements for the post-heating repair welding treatment are added for the connection corner between the post of side frame central frame and the spring cushion cap as well as the area (R+45)mm around the corner (see 3.9.3.2; 3.8.2.3, Edition 2006);
——The requirements for static load and fatigue tests are modified (see 3.11; 3.12, Edition 2006);
——The requirements for specimen preparation are added (see 4.1);
——The methods for surface roughness inspection are added (see 4.5.1);
——The methods for internal quality inspection are added (see 4.6);
——The inspection method for geometric dimension of castings are added (see 4.7);
——The rules for type inspection, periodic inspection and end-of-manufacturing inspection are added (see 5.1, 5.2 and 5.3);
——The rules for mechanical property inspection of bolster and side frame in case of insufficient test rods are deleted (see 4.2.8, Edition 2006);
——The requirements for marking are modified (see 6.1; 5.1, Edition 2006);
——The requirements for quality certificate are modified (see 6.2; 5.2, Edition 2006);
——The division methods for Parts A and B of ZK7 bolster and side frame are added (see Annex A);
——The metallographic atlas for metallographic microstructure examination of Grade B cast steel (ZG25MnNi) and Grade C cast steel (ZG25MnCrNiMo) are deleted (see Annexes A and B, Edition 2006);
——The requirements for qualified level of Parts A and B of bolster and side frame upon radiographic testing are added (See Annex C);
——The schematic diagrams are added as to dissected part for compactness inspection of ZK7 bolster and side frame (see Annex E);
——The position requirements are added as to the thickness measurement points for important parts of the bolster and side frame are added (see Annex F).
This standard was proposed by and is under the jurisdiction of CRRC Qishuyan Locomotive & Rolling Stock Technology Research Institute Co., Ltd.
Previous editions of this standard are as follow: TB/T 3012-2001 and TB/T 3012-2006.
Cast Steel Bolster and Side Frame for Railway Freight Car
1 Scope
This standard specifies technical requirements, inspection methods, inspection rules, marking and quality certificate and records for Grade B steel (ZG25MnNi), Grade B+ steel (ZG25MnCrNi) and Grade C steel (ZG25MnCrNiMo) bolsters and side frames for railway freight car.
This standard is applicable to the manufacture and inspection of Grades B, B+ and C steel bolster and side frame for railway freight car.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 222 Permissible Tolerances for Chemical Composition of Steel Products
GB/T 223 Methods for Chemical Analysis of Iron, Steel and Alloy
GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature (GB/T 228.1-2010, ISO 6892-1: 2009 MOD)
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method (GB/T 229-2007, ISO 148-1: 2006, MOD)
GB/T 6394 Metal-methods for Estimating the Average Grain Size
GB/T 6414-1999 Castings - System of Dimensional Tolerances and Machining Allowances (eqv ISO 8062: 1994)
GB/T 15056 Evaluation Method on Cast Surface Roughness
JB/T 5105 Casting Form Pattern Draft
TB/T 1959 Static Load and Fatigue Test of Bolster and Side Frame for Railway Freight Car
TB/T 2451 Metallographic Inspection for Non-metallic Inclusion in Cast Steel
TB/T 2942 General Technical Specifications of Steel Castings for Rolling Stock
TB/T 3105.1 Nondestructive Testing of Cast Steel Bolster and Side Frame for Railway Freight Car - Part 1: Radiographic Testing
TB/T 3105.3 Nondestructive Testing of Cast Steel Bolsters and Side Frames for Railway Freight Car - Part 3: Magnetic Particle Testing
TB/T 3105.4-2014 Nondestructive Testing of Cast Steel Bolsters and Side Frames for Railway Freight Car - Part 4: Digital Radiography and Industrial Computed Tomography Testing
TB/T 3211 Imperfections of Radiographic Testing for Steel Castings for Rolling Stock
TB/T 3212.1 Metallographic Atlas for Metallographic Microstructure Examination of Low Alloy Cast Steel for Rolling Stock - Part 1: Grades B and B+ Cast Steel
TB/T 3212.2 Metallographic Atlas for Metallographic Microstructure Examination of Low Alloy Cast Steel for Rolling Stock - Part 2: Grades C Cast Steel
3 Technical Requirements
3.1 General requirements
3.1.1 The bolster and side frame shall be in accordance with this standard as well as those specified in the technical documents and product drawings approved via established procedures.
3.1.2 The two important parts, i.e., A and B, shall be determined according to the stress state of the bolster and side frame and then specified in the product drawing. See Annex A for the division of Parts A and B of bolster and side frame.
3.2 Chemical composition
The chemical composition of the steel shall be in accordance with those specified in Table 1.
Table 1 Chemical Composition
Grade Chemical composition (mass fraction)
%
C≤ Si≤ Mn≤ P≤ S≤ Cu≤ Ni≥ Cr≤ Mo≤
Grade B 0.28 0.40 1.00 0.030 0.030 0.30 0.30 — —
Grade B+ 0.29 0.50 1.00 0.030 0.030 0.30 0.20 0.50 —
Grade C 0.28 0.40 1.50 0.030 0.030 0.30 0.35 0.60 0.30
For Grades B and B+ steels, if the carbon content is lower than the maximum value specified, the manganese content is allowed to be 0.04% higher than the specified maximum value each time the carbon content is reduced by 0.01%, but the maximum manganese content shall not be greater than 1.20%.
3.3 Mechanical property
3.3.1 The mechanical property of steel test rod shall be in accordance with the relevant requirements of TB/T 2942.
3.3.2 Where the products are randomly inspected or it is required by the customer, the mechanical property of cast steel may be evaluated with a physical specimen of which the mechanical properties shall be in accordance with the relevant requirements of TB/T 2942.
3.4 Metallographic phase
The metallographic analysis of cast steel covers the evaluation of nonmetallic inclusion, grain size and metallographic structure. Non-metallic inclusions shall be evaluated according to TB/T 2451 and shall be in accordance with those specified in Table 2; the grain size of the product shall be evaluated according to GB/T 6394, and the conformity level shall be stricter than or equal to Grade 6; the metallographic structure of Grade B and B+ steels shall be evaluated in accordance with TB/T 3212.1, and that of Grade C steel shall be evaluated in accordance with TB/T 3212.2.
Table 2 Rating of Non-metallic Inclusions in Cast Steel
Inclusion classification Conformity level Rating chart
Type I (globular) inclusion Thin: Grades 1~3; thick: Grade 1 Third rating chart
Type II (point-net) inclusion Grade 1~Grade 2 Second rating chart
Type III (dotted) inclusion Thin: Grades 1~3; thick: Grades 1 Third rating chart
Type IV (aluminum oxide cluster) inclusion Grade 1 Fourth rating chart
3.5 Process requirements
3.5.1 The cast steel shall be smelted with electric arc furnace and refining furnace.
3.5.2 The residual aluminum in the steel shall be controlled within 0.020%~0.080%. The reducing slag (FeO) in at least one melting furnace shall be taken every week to measure the reducing slag (FeO) content which shall not be greater than 1.0%; the keel block of the steel in at least one furnace No. shall be taken to inspect the oxygen content of the steel, which shall not be greater than 0.0060%.The residual aluminum, reducing slag (FeO) and oxygen content in steel will not be used as the basis for product delivery.
3.5.3 After tapping (in the pouring pot), the molten steel shall be killed for at least 5min and the pouring temperature shall not exceed 1,585°C.
3.5.4 Automatic integral core setting process shall be adopted for bogie bolsters and side frames with axle weights of 25t and above. Continuous heat treating furnace process shall be adopted for bogie bolsters and side frames with axle weights of 25t and above.
3.5.5 The bolster and side frame shall be subjected to heat treatment. Bolster and side frame made of Grades B and B+ steels shall be subjected to normalizing or normalizing & tempering heat treatment, and those made of Grade C steel shall be subjected to normalizing and tempering heat treatment. Where re-heat treatment is necessary, the frequency of re-heat treatment shall not exceed two times (the frequency of tempering is unlimited).The heat treatment of bolster and side frame shall be in accordance with the relevant requirements of TB/T 2942.
3.5.6 Dry knockout shall be adopted for bolster and side frame. During shake-out, the temperature of the casting shall not be higher than 540°C, the method of sand removal and its cooling rate shall not impair the quality of the casting.
3.5.7 After final heat treatment, the bolster and side frame shall not be cleaned via thermal method.
3.5.8 The temperature for correcting the distorted bolster and side frame shall not exceed 850°C; the castings corrected after heat treatment shall be heat treated and inspected again.
3.6 Surface quality
3.6.1 The surface of bolster and side frame shall be free of cracks via visual inspection; and the sand burning that impedes use and inspection shall be removed.
3.6.2 Unless it is otherwise specified in the product drawing and technical documents, the surface roughness of castings shall be NMR Ra100.
3.6.3 As for the castings, the flying edge and burrs presenting on the outer edge and the edges of the holes shall be totally removed and the edges shall be rounded; the conspicuous raised surface on the casting shall be polished flat and smooth.
3.6.4 The residual casting head on non-machined surface shall not exceed 3mm and it shall be smoothly transitioned to the surrounding casting surface.
3.6.5 Parts A and B of the bolster and side frame shall be free from visible chipping marks or nicks; the depth of those chipping marks and nicks on other parts shall not be greater than 2mm;chipping marks and nicks produced during manufacturing are allowed to be removed by grinding and shall be smoothly transitioned to the surround part, but the wall thickness at the ground part shall not be less than the minimum allowable size.
3.6.6 The non-machined casting surface within a radius of 25mm around the center of bolt (rivet) hole shall be flat and smooth.
3.6.7 The following defects are allowed to be left on the bolster without repair:
a) Local dent with a casting wall thickness no less than the minimum allowable value specified in the drawing and a depth less than or equal to 2mm after cleaning, which shall be so finished as to transition smoothly to the surrounding casting surface;
b) Local protrusions which are less than or equal to 2mm in height and have no influence on processing and assembly;
c) Gas holes scattered on the bolster surface (excluding Part A), which are less than or equal to 2mm, 5mm and 3pcs/cm2 in diameter, depth and density.
3.6.8 The following defects are allowed to be left on the side frames without repair:
a) Local dents spaced less than 100mm on Part A, of which the casting wall thickness is no less than the minimum allowable value specified in the drawing, the depth is less than or equal to 2mm, and the maximum dimension is less than or equal to 10mm after cleaning; such dents shall be so finished as to transition smoothly to the surrounding casting surface;
b) Local dent presenting on other parts with a casting wall thickness no less than the minimum allowable value specified in the drawing and a depth less than or equal to 3mm after cleaning, which shall be so finished as to transition smoothly to the surrounding casting surface;
c) Local protrusions which are less than or equal to 2mm in height and have no influence on processing and assembly;
d) Gas holes scattered on the side frame surface (excluding Part A), which are less than or equal to 2mm, 5mm and 3pcs/cm2 in diameter, depth and density respectively.
3.6.9 The magnetic particle testing of the surface shall be in accordance with the following requirements:
a) magnetic particle testing shall be performed on Parts A and B of the bolsters and side frames as well as other parts required to be tested in the drawing. The parts to be tested shall be free of cracks or transverse linear magnetic trace of defects;
b) for the bolster, the length of magnetic particle indication for a single longitudinal linear defect is allowed to be no larger than 5mm; the accumulative length of magnetic particle indication for dispersed defects with length greater than or equal to 3mm and less than 5mm is allowed to be no larger than 30mm within a rectangular area (with the long side no larger than 150mm) of 2,500mm2;
c) for the side frame, the length of magnetic particle indication for a single longitudinal linear defect is allowed to be no larger than 5mm; the accumulative length of magnetic particle indication for dispersed defects with length greater than or equal to 3mm and less than 5mm is allowed to be no larger than 24mm within a rectangular area (with the long side no larger than 150mm) of 2,500mm2;
3.6.10 In case of any of the following defects, the bolster shall be discarded:
a) transverse penetrating cracks on Parts A and B;
b) other penetrating casting defects presenting on Parts A and B with a single area exceeding 30 cm2 or a total area exceeding 60 cm2.
3.6.11 In case of any of the following defects, the side frame shall be discarded:
a) transverse penetrating cracks on Parts A and B;
b) the following defects presenting on Part A: other penetrating cracks with a length exceeding 50mm; or a single penetrating defect of other type with the area exceeding 20cm2, or more than one penetrating defects of other type with the area exceeding 20cm2;
c) the following defects presenting on Part B: other penetrating cracks with a length exceeding 50mm; or a single penetrating defect of other type with the area exceeding 25cm2, or more than one penetrating defects of other type with the area exceeding 50cm2;
Contents of TB/T 3012-2016
Foreword i
1 Scope
2 Normative References
3 Technical Requirements
4 Inspection Method
5 Inspection Rules
6 Marking and Quality Certificate
7 Record
Annex A (Normative) Partitioning Methods for Part A and Part B of Bolsters and Side Frames
Annex B (Normative) Bolster and Side Frame Compactness Standard Picture
Annex C (Normative) Radiography Qualification Grades for Part A and Part B of Bolster and Side Frame
Annex D (Normative) Measuring Basis of Bolster and Side Frame
Annex E (Normative) Bolster and Side Frame Compactness Inspection and Dissection Positions
Annex F (Normative) Location of Thickness Measuring Points for Important Parts of Bolster and Side Frame
