Heat resistant steel rod for valve material

Heat resistant steel rod for valve material

This scale defines the size, shape, technical requirements, test methods, acceptance rules, packaging marks and quality certification of heat-resistant steel rods (round steel, square steel, flat steel and hexagonal steel, hereinafter referred to as steel rods). The terms in the following documents become terms of this scale by reference to this scale. For dated citations, all subsequent amendments (excluding erratum) or revisions are not applicable to this scale, however, parties to agreements under this scale are encouraged to explore the availability of such editions.

1 range

This scale defines the size, shape, technical requirements, test methods, acceptance rules, packaging marks and quality certification of heat-resistant steel rods (round steel, square steel, flat steel and hexagonal steel, hereinafter referred to as steel rods).

This scale is applicable to hot rolled, forged or cold worked steel rods with dimensions (diameter, side length, thickness or opposite side spacing, hereinafter referred to as dimensions) not greater than 250mm. Hot rolled and forged steel rods with sizes greater than 250mm or cold worked steel rods with sizes greater than 120mm are also available upon negotiation between the parties.

2 Normative reference files

The terms in the following documents become terms of this scale by reference to this scale. For dated citations, all subsequent amendments (excluding erratum) or revisions are not applicable to this scale. However, parties to agreements under this scale are encouraged to investigate the availability of *** versions of these documents. For undated references, the  version is applicable to this scale.

4 Order Contents

Contracts or orders placed according to this scale shall include the following:

5 Classification

5. 1 Steel rods can be divided into four types according to their structure characteristics: Austenitic type, ferritic type, martensitic type and precipitation-hardened type.

5. 2 Steel rods are divided into the following two categories according to different processing methods. The use and processing method of the steel rod shall be indicated in the contract. If not, the supply shall be made of cutting steel.

Size, shape, weight and allowable deviation

6. 1 Size, shape and allowable deviation of hot rolled round and square copper

The dimensions, shapes and tolerances of hot rolled round and square steels shall conform to the specification of GB/T 702-2004, and the detailed requirements shall be stated in the contract. If not indicated, 2 groups of GB/T 702-2004 should be performed.

6. 2 Size, shape and allowable deviation of hot rolled flat steel

The dimensions, shapes and allowable deviations of the hot rolled flat steel shall conform to the specifications specified in GB/T 704-1988 and the detailed requirements shall be stated in the contract. If not indicated, the standard GB/T 704-1988 scale shall be applied.

6. 3 Dimensions, shapes and allowable deviations of hot rolled hexagon steel

The dimensions, shapes and tolerances of hot-rolled hexagonal steel shall conform to the specifications specified in GB/T 705-1985, and the detailed requirements shall be stated in the contract. Not indicated in GB/T 705-1985 scale 2 group execution.

6. 4 Forging round and square steel size, shape and tolerance

The dimensions, shapes and tolerances of forged round and square steels shall be in accordance with the specification of GB/T 908-1987, and the detailed requirements shall be stated in the contract. If not indicated, execute according to GB/T 908-1987 scale 2 group.

6. 5 Dimension, shape and allowable deviation of forged flat steel

The dimensions, shapes and tolerance deviations of forged flat steel shall conform to the delineation of GB/T 16761-1997, and the detailed requirements shall be stated in the contract. If not indicated, execute in 2 groups according to GB/T 16761-1997 scale.

6.6 Dimension, shape and tolerance deviation of cold working steel rod

6.6.1 Dimensions and allowable deviations

6.6.1.1 The size tolerance deviation of cold-worked steel rods shall conform to the demarcations in Table 1, and the level of tolerance deviation shall be indicated in the contract. If not, it shall be executed according to h11l. The applicable range of cold-worked steel rod tolerance deviation level can be selected according to Table 2.

6.6.1.2 For steel rods undergoing heat treatment and pickling after cold working, the allowable deviation shall be twice of the looser deviation listed in Table 2.

6. 6. 2 Shape and tolerance deviation

The bending degree and unroundness (square) or side length difference of cold working steel rod shall conform to the demarcation of Table 3. Steel for automatic cutting shall be specified in the contract.

Table 3 Bending degree, square degree or side length difference of cold working steel bar

6. 7 Weight

Steel rods are generally delivered by actual weight.

Steel rods can be delivered in the state of heat treatment or no heat treatment. When ordering, you can refer to 7.3.1~7.3.5 to select the state of delivery and indicate it in the contract. Delivery without heat treatment if not specified. See Table A.1 Table A.4 for the heat treatment rail system of various types of steel bars in Appendix A. Solid solution treatment or annealing treatment should be chosen for the precipitation hardening steel bars according to the microstructure of the steel. The annealing rail system shall be determined by negotiation between the supply and demand parties. In the case of no agreement, the annealing temperature is generally 650℃~680℃. As agreed by both parties, precipitation-hardened steel rods (except 05Cr17Ni4Cu4Nb) can not be treated.

Mounting: Heat resistant steel rod of valve material (1)

7 Technical Requirements

7.1 Brand and chemical composition

7.1.1 The grade of steel, the same number code and the chemical composition (smelting analysis) shall conform to the demarcations in Table 4-7.

7.1.2 The allowable deviation of the chemical composition of the steel rod shall be in accordance with GB/T222.

7.2 Smelting method

Unless otherwise specified in the contract, the process of initial steelmaking (water) and off-furnace refining shall be used.

7.3 Delivery status

Steel rods can be delivered in heat-treated or non-heat-treated state. When ordering, you can refer to 7.3.1~7.3.5 to select the delivery state and indicate it in the contract. Delivery without heat treatment if not specified. Heat treatment rail system for all types of steel bars

7.3.1 Austenitic steel rod for cutting shall be treated by solution or annealing, or may not be treated after negotiation by both parties. The steel rod for hot pressure processing shall not be treated by solution or annealing.

7.3.2 Ferritic steel bars shall be annealed and may not be treated after negotiation by both parties.

7.3.3 Mahalanobsidian steel rod shall be annealed.

7.3.4 Precipitation hardening steel rods should be treated with solution or annealing according to the structure of the steel. The annealing rail system shall be determined by negotiation between the supply and demand parties. In the case of no agreement, the annealing temperature is generally 650℃~680℃. As agreed by both parties, precipitation-hardened steel rods (except 05Cr17Ni4Cu4Nb) can not be treated.

7.3.5 Cold-worked steel rods that have been cold-drawn, polished, cut or made by a combination of these methods may be delivered after heat treatment and pickling as required by the demander.

7.4 Mechanical function

7.4.1 The heat treatment rail system of various types of steel bars or samples shall be defined according to Tables A.1~ A.4 in Appendix A. The size of sample blank for heat treatment is generally 25mm. When the size of steel rod is less than 25mm, the original size steel rod is used for heat treatment. The mechanical function of the steel bar without heat treatment after cold drawing shall be determined by negotiation between the supply and demand parties.

7.4.2 After heat treatment of steel rods (except martensitic steel annealing), the sample shall not be subjected to heat treatment, and its mechanical functions shall be in accordance with each other

7.4.3 For steel bars without heat treatment, the mechanical properties of the sample blank after heat treatment shall conform to the demarcation of Table 8-11 respectively.

7.4.4 The mechanical function of precipitate-hardened steel bars shall indicate the heat treatment group in the contract. If not, it shall be executed as Group 1.

7.4.5 If the supplier can ensure that the mechanical function is qualified, the mechanical function test of all departments or departments can be omitted.

7.5 Low-power tissue

7.5.1 Visually visible shrinkage holes, bubbles, cracks, inclusions, peeling and white spots shall not be allowed on the acid leaching low-power test piece of the steel bar in cross section. The steel bar for cutting shall have defects such as subcutaneous inclusions with a depth not more than half of the nominal dimensional tolerance.

7.5.2 The qualification level of acid leached low-growth tissue shall conform to the demarcation in Table 12. When the demander requires 1 set, it shall be indicated in the contract. For steel rods larger than 200mm, the qualification level of lower size microstructure shall be determined by both parties through negotiation.

7.5.3 If the Supplier can guarantee, it agrees to use ultrasonic inspection or other non-destructive inspection methods instead of low-power inspection.

Table 12 Lower tissue qualification level

7.6 Hot top forging

7.6.1 The steel used for hot top forging (as indicated in the contract) shall be subjected to hot top forging test. The height of the sample after hot top forging shall be one third of the height of the original sample. There shall be no cracks or cracks in the sample after top forging.

7.6.2 For steel rods larger than 80mm, if the supplier can ensure that the top forging test is qualified, the test may not be carried out.

7.7 Surface quality

7.7.1 The surface of the steel rod for pressure processing shall not have cracks, scars, folds or inclusions. If the above defects are necessary, the depth shall conform to the demarcations in Table 13, the width shall not be less than 5 times of the depth, and the unified section shall not be more than one deep. Individual fine scratches, indentation, pitting and small cracks with depth not exceeding 0.20mm are allowed from the actual size not exceeding half of the nominal size tolerance. Round steel rod for pressure processing, the surface can be turned or peeled according to the agreement between the parties.

Table 13 Allowable depth of steel rod surface defects for pressure processing

7.7.2 Steel rods for machining shall be permitted to have local defects not exceeding those specified in Table 14 from their nominal dimensions.
7.7.3 The surface of the cold-worked steel rod shall be clean and smooth, and no cracks, scars, folds, inclusions, cracks or oxide skin shall be allowed. Steel rods delivered in heat treatment condition are allowed to have oxidation color. In the absence of special requirements, the surface of the steel rod is allowed to have individual scratches, scratches, dark spots, pitting and other defects whose depth from the actual size does not exceed the nominal dimensional tolerance.

7.7.4 The surface of the steel rod that has been turned or peeled, polished or polished shall not have defects affecting the use.

7.7.5 After negotiation by both parties and indicated in the contract, pickling, turning and other methods may be used to remove the black skin generated by heat treatment.

7.8 Special Requirements

According to the requirements of the demander and by agreement between the two parties, the following special requirements of steel rods can be supplied.

8 Test method

The inspection items and test methods of each batch of steel rods shall conform to the delineation in Table 15.

9 Maintenance Rules

9.1 Inspection and acceptance

The inspection and acceptance of steel rods shall be carried out by the technical quality monitoring section of the supplier.

9.2 Batch Rules

Steel rods shall be inspected and accepted by lot. Each batch is composed of steel rods with unified grade, furnace number, processing method, size and delivery status (unified heat treatment furnace times). For steel smelted by electroslag remelting, under the premise that the process is not chaotic and the technical requirements of this scale can be guaranteed, it is agreed to deliver the steel in batch with the smelting master furnace number of consumable electrode, and it is indicated in the quality certificate.

9.3 Sampling site and sampling POTS

The sampling location and number of each batch of steel rod inspection shall conform to the delineation in Table 15.

Table 15 Maintenance items, number of samples, sampling location and test method of steel rod

9.4 Reinspection and judgment rules

9.4.1 Rules for reinspection and judgment shall be delimited according to GB/T 17505.

9.4.2 If the supplier can ensure that the steel rods are qualified, the supplier agrees to use the billet as a substitute for the billet and large instead of small for the inspection results of the mechanical function, low microstructure and non-metallic inclusions of the steel rods or billets with the same furnace number.

Packing, marking and quality certificate

The packaging, marking and quality certificate of steel rods shall conform to the relevant specification in GB/T 2101.