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GB/T 37681-2019 English PDF (GBT37681-2019)

GB/T 37681-2019 English PDF (GBT37681-2019)

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GB/T 37681-2019: Heavy steel castings -- General technical specification

This Standard specifies the ordering requirements, manufacturing process, technical requirements, inspection rules and test methods, acceptance and delivery, etc. of heavy steel castings. This Standard applies to heavy steel castings cast using the sand mold or casting mold with equivalent thermal conductivity as the sand mold.
GB/T 37681-2019
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.80
J 31
Heavy steel castings - General technical specification
ISSUED ON: JUNE 04, 2019
IMPLEMENTED ON: JUNE 04, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 6
4 Ordering requirements and documents ... 8
5 Manufacturing process ... 9
6 Technical requirements ... 12
7 Inspection rules and test methods ... 14
8 Acceptance and delivery ... 19
Appendix A (Informative) Commonly-used material standards for heavy steel castings ... 22
Heavy steel castings - General technical specification
1 Scope
This Standard specifies the ordering requirements, manufacturing process, technical requirements, inspection rules and test methods, acceptance and delivery, etc. of heavy steel castings (hereinafter referred to as ?€?castings?€?). This Standard applies to heavy steel castings cast using the sand mold or casting mold with equivalent thermal conductivity as the sand mold.
2 Normative references
The following documents are indispensable for the application of this document. For the dated references, only the editions with the dates indicated are applicable to this document. For the undated references, the latest edition (including all the amendments) are applicable to this document.
GB/T 222 Permissible Tolerances for Chemical Composition of Steel
Products
GB/T 223 (all parts) 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 228.2 Metallic materials - Tensile testing - Part 2: Method of test at elevated temperature
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method
GB/T 231.1 Metallic materials - Brinell hardness test - Part 1: Test method GB/T 232 Metallic materials - Bend test
GB/T 2039 Metallic materials - Uniaxial creep testing method in tension GB/T 3375-1994 Welding terminology
GB/T 4334 Corrosion of metals and alloys - Test methods for intergranular corrosion of stainless steels
GB/T 4336 Carbon and low-alloy steel - Determination of multi-element
contents - Spark discharge atomic emission spectrometric method (routine method)
GB/T 5611-2017 Foundry terminology
GB/T 5677 Castings - Radiographic testing
GB/T 5678 Sampling methods of spectrochemical analysis for cast alloys
GB/T 6394 Metal - Methods for estimating the average grain size
GB/T 6414-2017 Castings - Dimensional Tolerances and Geometrical
Tolerances and Machining Allowances
GB/T 6477-2008 Metal-cutting machine tools - Terminology
GB/T 7233.1 Steel castings - Ultrasonic examination - Part 1: Steel castings for general purposes
GB/T 7233.2 Steel castings - Ultrasonic examination - Part 2: Steel castings for highly stressed components
GB/T 9443 Penetrant testing for steel castings
GB/T 9444 Magnetic particle testing for steel castings
GB/T 9452 Testing method for working zone of heat treatment furnace
GB/T 11170 Stainless steel - Determination of multi-element contents - Spark discharge atomic emission spectrometric method (Routine method)
GB/T 11261 Steel and Iron - Determination of oxygen content - The pulse heating inert gas fusion-infra-red absorption method
GB/T 11351-2017 Mass tolerances of casting
GB/T 11352-2009 Carbon steel castings for general engineering purpose
GB/T 13298 Inspection methods of microstructure for metals
GB/T 13299 Steel - Determination of Microstructure
GB/T 15056 Casting surface roughness - Appraising method
GB/T 17505-2016 Steel and steel products - General technical delivery
requirements
GB/T 20066 Steel and Iron - Sampling and Preparation of Samples for the Determination of Chemical Composition
[GB/T 5611-2017, definition 3.1.21]
3.5 Test lug; cast-on sample
The test bar attached to the casting which does not damage the casting body after cutting.
Note: After the test lug is processed into a sample, it is used to inspect the chemical composition, metallographic structure, and mechanical properties, etc. of the casting. [GB/T 5611-2017, definition 3.1.22]
3.6 Welding groove for cast defect
The molded profile with a certain geometrical shape and a certain slope for the purpose of repair-welding deep cast defects. Generally, it may be formed by tools such as machining, carbon arc air gouging, and grinding wheel.
3.7 Melting
The process and operation in which the metal is converted from solid state to liquid state by heating, and then subjected to composition adjustment and refining to meet the requirements of purity, temperature, and composition. [GB/T 5611-2017, definition 3.5.1]
3.8 Pad
The excess metal which gradually thickens along the section of the casting toward the riser along the riser feeding distance in order to increase the feeding effect of the riser.
[GB/T 5611-2017, definition 5.2.26]
3.9 Dressing and finishing
The process and operation which make the surface quality or shape and
dimension of the casting meet the standard requirements by means of repair welding, carbon arc air gouging, grinding wheel grinding, shot blasting (sand blasting), etc.
Note: REWRITE GB/T 5611-2017, definition 8.3.7.
3.10 Carbon equivalent
CONVERT the content of alloying elements in steel, according to their action, into the equivalent content of carbon, which is equal to the sum of the converted carbon content of the content of various alloying elements and the actual total process shall be recorded in detail. During the repair welding process, if defects such as cracks, incomplete fusion, and lack of penetration which affect the quality are found, measures shall be taken timely to remove the defects. The repair welding can be continued after confirming that the defects have been removed.
5.5.3 Post-weld heat treatment and inspection
5.5.3.1 Post-weld heat treatment
In principle, after the repair welding of the casting is completed, the repair welding zone shall be subjected to stress relief annealing (except for products with special materials or special requirements).
The post-weld stress relief annealing temperature shall be lower than the tempering temperature during the performance heat treatment. In special cases, if the post-weld stress relief annealing temperature is higher than the tempering temperature during the performance heat treatment, the performance test bar shall be subjected to stress relief annealing with the furnace and to mechanical property testing again. The stress relief annealing holding time shall be determined according to the depth of the repair welding for the defect and the wall thickness of the product. It is recommended to keep the heat for 2 h~4 h per 100 mm. The minimum holding time is 3 h.
5.5.3.2 Post-weld inspection
The repair welding position shall, according to the technical requirements of the product, be subjected to non-destructive testing and surface hardness
inspection. Unless otherwise specified, the inspection shall be carried out according to the non-destructive testing requirements of the casting body at the position where the repair welding zone is located. When the hardness
inspection of the repair welding position is required in the drawing or the ordering agreement, after the stress relief annealing, it shall carry out the surface hardness inspection.
5.6 Machining
5.6.1 Machining allowance
Unless otherwise specified, the machining allowance shall be selected by the manufacturer itself or in accordance with the provisions of GB/T 6414-2017. But it shall ensure that the dimensions of the casting product after machining comply with the drawings or agreements.
5.6.2 Stress relief annealing after machining
purchaser shall specify the sampling position and acceptance level of each inspection.
The sample for metallographic inspection shall be prepared from the test bar for mechanical properties. The preparation of the metallographic sample shall be not less than 6 mm from the surface of the test bar blank. If the purchaser requires inspection of the body metallography, the inspection position shall be agreed by both the supplier and the purchaser.
6.4 Non-destructive testing
The castings shall, after dressing and finishing and machining, be subjected to non-destructive testing. However, since the shape and structure of the castings have a great influence on the internal quality assurance, the requirements for the method, area, and acceptance level, etc. of the non-destructive testing shall be in accordance with the product design or use requirements. It shall be agreed by both the supplier and the purchaser.
6.5 Appearance, shape, dimensional tolerances, and mass tolerances
6.5.1 Appearance quality requirements
It shall clean up the burnt-on sand, sand inclusion, split edge, burr, and scale on the casting. The surface roughness of the casting shall be in accordance with the requirements of the drawings or the ordering agreement.
There shall be no defects affecting the use on the casting surface. If there are defects, repair welding may be carried out.
6.5.2 Dimensional tolerances
The dimensional tolerances of the castings shall comply with the provisions of the drawings or the ordering agreement. If there are no provisions in the drawings or the ordering agreement, the dimensional tolerances of the castings shall comply with the requirements of Grade DCTG13 to DCTG15 in GB/T
6414-2017.
6.5.3 Mass tolerances
When ordering, both the supplier and the purchaser may agree on the mass tolerances of the casting. If not required by the purchaser, the mass tolerances shall meet the requirements of Grade MT13 to MT15 in GB/T 11351-2017.
6.6 Requirements for special tests
When required by the purchaser, requirements for special tests (such as metallographic, tensile at elevated temperature, high-temperature short requests acceptance of the performance after the final heat treatment, it shall be specified in the ordering requirements.
7.1.4 Inspection lot
7.1.4.1 When the mass (net mass) of the casting is less than 3 t, according to the principle of double-same (same-furnace melting, same-furnace heat
treatment), a set of physical and chemical inspections are carried out. 7.1.4.2 When the mass (net mass) of the casting is greater than or equal to 3 t, each product shall be subjected to a set of physical and chemical inspections. 7.1.5 Processing of sample
The sample is taken from the test bar by machining, with a minimum distance of 6 mm from the casting surface and a minimum distance of 30 mm from the thermal cutting surface.
7.2 Provisions on invalid tests
When the test result does not meet the requirements, if the following conditions exist, the test will be invalid. When the test is invalid, double quantity of samples may be taken again from the same test portion or from the test portion near the adjacent position of the unqualified test bar for retest. The retest data is used as the test result.
a) Improper processing of sample (There are tool marks, no chamfers, etc.); b) Improper installation of sample or improper operation of testing machine; c) There are defects on the sample (There are obvious cast defects such as slag inclusion, pores, and shrinkage porosity at the fracture position); d) In the tensile test, it breaks at a position outside the gage point. 7.3 Chemical composition analysis
7.3.1 Provisions on sampling and sample preparation
Sampling and sample preparation for chemical composition analysis shall be carried out in accordance with the provisions of GB/T 20066 or GB/T 5678. 7.3.2 Melting analysis
The sample for chemical composition melting analysis of castings shall be sampled from the ladle during the casting process or before tapping. It shall take 1 sample per ladle. If a single casting is cast in multiple ladle, each ladle the supplier shall select at least 2 representative positions for testing. The surface roughness Ra of the test position shall be ???3.2 ??m. If the hardness test tool has provisions for the test surface of the casting, it shall meet the corresponding provisions.
7.4.3.3 Brinell hardness test is carried out in accordance with the provisions of GB/T 231.1.
7.4.3.4 Unless otherwise specified, for the hardness of the same area of the same sample or body, it shall measure 3 hardness values. The average of the 3 hardness values shall comply with the regulations.
7.5 Non-destructive testing
7.5.1 Penetrant testing
The casting surface may be subjected to penetrant testing, to detect the surface defects. Penetrant testing is carried out in accordance with the provisions of GB/T 9443.
7.5.2 Magnetic particle testing
The casting may be subjected to magnetic particle testing, to detect the surface or near-surface defects of the casting. Magnetic particle testing is carried out in accordance with the provisions of GB/T 9444.
7.5.3 Ultrasonic testing
The internal defects of the casting may be subjected to ultrasonic testing. Ultrasonic testing is carried out according to the provisions of GB/T 7233.1 or GB/T 7233.2.
7.5.4 Radiographic testing
The internal defects of the casting may be also subjected to radiographic testing. Radiographic testing is carried out in accordance with the provisions of GB/T 5677.
7.6 Surface quality, shape, dimension, and mass inspection
7.6.1 Surface quality inspection
The casting surface is visually inspected. The surface roughness is evaluated in accordance with the provisions of GB/T 15056.
7.6.2 Shape and dimension inspection
7.8.2 When the tensile test fails, samples may be taken from a test bar near the adjacent position of the unqualified test bar for double retest. If the 2 test results comply with the requirements of the purchaser, the tensile properties of this lot are qualified; otherwise the supplier may handle as specified in 7.9.
7.8.3 When the impact test fails, samples may be taken from a test bar near the adjacent position of the unqualified test bar for double retest. If the arithmetic mean of the test results of the retested 6 impact samples reaches the mean specified by the purchaser, and only the test results of 2 samples are allowed to be lower than the specified mean but each shall not be lower than 70% of the specified value, otherwise the supplier may handle as specified in 7.9. 7.8.4 When the hardness is unqualified, samples may be taken from a test bar near the adjacent position of the unqualified test bar for double retest. If the arithmetic mean of the retest results meets the requirements of the purchaser, the hardness of this lot is qualified; otherwise the supplier may handle as specified in 7.9.
7.8.5 If the special test fails, a retest may be conducted. The retest rules shall be agreed by the supplier and the purchaser.
7.8.6 When the retested unqualified object is a spot-check sample, and the test unit represented by the spot-check sample is composed of the same type of castings of non-double-same (same melting, same heat treatment) heat and lot, samples may be taken again from the remaining products of the unit for
inspection. The sampling position and quantity shall be agreed by the supplier and the purchaser. If the test results of the re-sampling comply with the requirements of the purchaser, the performance of the remaining products of this unit shall be qualified; otherwise the supplier may handle as specified in 7.9. Samples which fail the first spot-check shall be disposed of in accordance with 7.9.
7.9 Reheat treatment
When the retest result still does not meet the requirements, the casting and the test bar may be heat treated again. Without the consent of the purchaser, the reheat treatment shall not exceed 2 times (The number of tempering is not limited). After reheat treatment, it shall, according to the provisions of 7.4~7.8, carry out the testing again. The testing content and the number of samples are the same as the original regulations.
8 Acceptance and delivery
8.1 Acceptance
Appendix A
(Informative)
Commonly-used material standards for heavy steel castings
This appendix gives a list of commonly-used material standards for heavy steel castings. For a specific product, it may also involve other standards than those listed.
GB/T 7659 Steel casting suitable for welded structure
GB/T 11352 Carbon steel castings for general engineering purpose
JB/T 3735 Steel Castings for Francis Runner
JB/T 6402 Heavy low alloy steel castings - Technical specification
JB/T 6403 Heavy heat-resisting steel castings - Technical specification JB/T 6404 Heavy high manganese steel castings - Technical specification JB/T 6405 Heavy stainless steel castings - Technical specification
JB/T 7024 Steel casting for 300MW and above turbine casing - Technical
specification
JB/T 7031 Steel castings for the end cover of the large grinding machines - Technical specification
JB/T 7349 Stainless steel blade castings for hydraulic turbines
JB/T 8709 The steel castings for the heavy rolling mill housing - Technical specification
JB/T 10264 Crown and band castings for Francis turbine welded runner
JB/T 11018 Specification for Cr10 stainless steel casting of steam turbine for supercritical and ultra-supercritical units
JB/T 11022 Specification for heavy hot-rolling work roll made of high
chromium cast steel
JB/T 11025 Specification of steel castings used for steam turbine of large nuclear generator units

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