GB/T 28415-2023Fire-resistant structural steel plate, sheet and strip (English PDF)

Foreword

This document was issued on 6 August 2023 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 March 2024.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

1 Scope

GB/T 28415-2023 covers steel plate, sheet and strip intended to hold its strength in a fire — the way the designation is composed, the ordering content, the size, shape and weight, the technical requirements, the test methods, the inspection rules, and the packaging, marking and quality certificate. Fire-resistant structural steel is defined here as steel to which a certain content of alloying elements such as molybdenum and chromium has been added, and the designation is assembled from the letter Q for yield strength, the specified lower limit of the upper yield strength, and the letters FR for fire resistance, so the grade mark itself tells a fabricator what the material is meant to do rather than leaving it to the mill certificate. That matters because ordinary structural steel gives up strength as it heats, and the usual answer — coating, encasement, sprayed protection — costs money on every member and has to survive the life of the building; a steel that keeps a defined part of its strength at elevated temperature changes that calculation. Inspection and acceptance are carried out by the supplier's quality inspection department. Used by steel mills, structural fabricators, and the designers and checking engineers who set fire protection for steel frames.

This document specifies designation expression method, ordering content, size, shape,

weight, technical requirements, test methods, inspection rules, packaging, marking and

quality certificates of fire-resistant structural steel plates, sheets and strips.

This document applies to steel plates with a thickness of no more than 150 mm and

steel sheets and strips with a thickness of no more than 25.4 mm and sheared steel plates

(hereinafter referred to as steel plates, sheets and strips) that are mainly used to

manufacture general structures and engineering structures with fire resistance.

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 223.3, Methods for chemical analysis of iron, steel and alloy. The diantipyryl

methane phosphomolybdate gravimetric method for the determination of

phosphorus content

GB/T 223.9, Iron, steel and alloy -- Determination of aluminium content -- Chrome

azurol S photometric method

GB/T 223.11, Iron, steel and alloy -- Determination of chromium content -- Visual

titration or potentiometric titration method

GB/T 223.14, Methods for chemical analysis of iron, steel and alloy. The N-benzoyl-

N-phenylhydroxylamine extraction photometric method for the determination of

vanadium content

GB/T 223.17, Methods for chemical analysis of iron, steel and alloy -- The

diantipyrylmethane photometric method for the determination of titanium content

GB/T 223.18, Methods for chemical analysis of iron steel and alloy -- The sodium

thiosulfate separation iodometric method for the determination of copper content

GB/T 223.23, Iron, steel and alloy -- Determination of nickel content -- The

dimethylglyoxime spectrophotometric method

GB/T 223.26, Iron, steel and alloy -- Determination of molybdenum content -- The

thiocyanate spectrophotometric method

GB/T 223.40, Iron, steel and alloy -- Determination of niobium content by the

sulphochlorophenol S spectrophotometric method

GB/T 223.60, Methods for chemical analysis of iron, steel and alloy -- The

perchloric acid dehydration gravimetric method for the determination of silicon

content

GB/T 223.63, Iron, steel and alloy -- Determination of manganese content -- Sodium

(potassium) periodate spectrophotometric method

GB/T 223.68, Methods for chemical analysis of iron, steel and alloy -- The potassium

iodate titration method after combustion in the pipe furnace for the determination of

sulfur content

GB/T 223.69, Iron, steel and alloy -- Determination of carbon contents -- Gas-

volumetric method after combustion in the pipe furnace

GB/T 223.79, Iron and steel -- Determination of multi-element contents -- X-ray

fluorescence spectrometry (Routine method)

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 232, Metallic materials -- Bend test

GB/T 247, General rule of package, mark and certification for steel plates (sheets)

and strips

GB/T 709, Dimension, shape, weight and tolerance for hot-rolled steel strip, plate

and sheet

GB/T 2970, Method for ultrasonic testing of thicker steel plates

GB/T 2975, Steel and steel products -- Location and preparation of samples and test

pieces for mechanical testing

GB/T 4336, Carbon and low-alloy steel -- Determination of multi-element contents

-- Spark discharge atomic emission spectrometric method (routine method)

GB/T 5313, Steel plate with through-thickness properties

GB/T 8170, Rules of rounding off for numerical values and expression and

judgement of limiting values

GB/T 14977, General requirement for surface condition of hot-rolled steel plates

GB/T 17505, 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 20123, Steel and iron -- Determination of total carbon and sulfur content

Infrared absorption method after combustion in an induction furnace (routine

method)

GB/T 20125, Low-alloy steel -- Determination of multi-element contents --

Inductively coupled plasma atomic emission spectrometric method

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1 fire-resistant structural steel

The steel that a certain content of alloying elements such as Mo, Cr, etc. is added to the

steel to improve the fire resistance.

4 Designation expression method

4.1 The designation of fire-resistant structural steel consists of the initial letter "Q" in

Chinese pinyin of the word "Qu" representing yield strength, the specified lower limit

value of the upper yield strength, the initial letter "FR" of English representing "fire

resistance" and the quality grade (codenamed B, C, D or E).

NOTE: Q+ specifies the lower limit value of upper yield strength + FR, referred to as "steel grade".

Example: Q420FRD, where:

Q - the initial letter "Q" in Chinese pinyin of the word "Qu" representing yield strength;

420 - the specified lower limit value of the upper yield strength, in megapascals (MPa);

FR - the initials of "fire resistant" in English;

D - the quality grade is D.

4.2 When steel plates, sheets and strips are required to have thickness-direction

properties, a symbol representing the thickness-direction (Z-direction) performance

of the steel plate thickness. The minimum allowable thickness of the steel plate shall be

ensured.

7.5.1.3 Surface defects of steel plates are allowed to be removed by grinding and other

methods. The cleaning area shall be smooth and without edges. The cleaning depth shall

not be greater than the negative deviation of the steel plate thickness. The minimum

allowable thickness of the steel plate shall be ensured.

7.5.1.4 If there are defects on the surface of the steel plate that cannot be cleaned

according to the provisions of 7.5.1.3, welding repair can be carried out after

negotiation between the supplier and the purchaser. The following requirements shall

be met:

a) Use appropriate welding methods;

b) Before welding repairs, use appropriate methods such as leveling or grinding to

completely remove harmful defects on the steel plate. The depth of the removed

portion is within 20% of the nominal thickness of the steel plate. The total

grinding area on one side shall be within 2% of the steel plate area;

c) There shall be no undercut or overlap on the edges of the welded parts of the steel

plates. The pile height shall be more than 1.5 mm higher than the rolling surface.

Then remove the pile height by leveling or grinding;

d) Heat treated steel plates shall be heat treated again after welding and repair.

7.5.1.5 After negotiation between the supplier and the purchaser, and stated in the

contract, the surface quality of the steel plate can be in accordance with the provisions

of GB/T 14977.

7.5.2 Steel sheets and strips, sheared steel plates

7.5.2.1 The surfaces of the steel sheets and strips shall not have scars, cracks, folds,

inclusions, air bubbles, and intrusion of iron oxide scale that would affect the use and

other harmful defects. The steel sheets and strips shall have no visible delamination.

7.5.2.2 The surfaces of the steel sheets and strips are allowed to have local defects such

as a thin layer of iron oxide scale, rust, slight pitting, scratches, etc. that do not affect

the use. However, its depth or height shall not exceed half of the steel sheet and strip

thickness tolerance. The allowable minimum thickness of the steel sheet and strip shall

be ensured.

7.5.2.3 The steel sheets and strips are allowed to be delivered with local defects, but the

defective part shall not exceed 6% of the total length of each coil of steel sheets and

strips.

7.5.2.4 After negotiation between the supplier and the purchaser, and stated in the

contract, the surface quality of the steel sheet and strip can be in accordance with the

corresponding

accuracy