This standard is drafted in accordance with GB/T 1.1-2020, Rules for drafting standards - Part 1: The structure and drafting of standardizing documents.

This standard supersedes GB/T 714-2015 Structural steel for bridges. Compared with GB/T 714-2015, in addition to structural adjustments and editorial revisions, the main technical changes are specified as follows:

a) The provisions for section steel products are deleted (Clause 1 of the 2015 edition);

b) Definitions of the terms thermomechanical rolling and atmospheric-corrosion-resistant steel are revised (see Clause 3; Clause 3 of the 2015 edition); c) The requirements for boron content are revised (see Table 1; Table 1 of the 2015 edition);

d) Four grades of thermomechanically rolled steel (Q390q, Q550q, Q620q, Q690q) and their corresponding chemical compositions are added (see Table 3, Table 6 and Table 7);

e) The lower limit requirements of manganese content for thermomechanically rolled steel are revised (see Table 3; Table 3 of the 2015 edition);

f) The atmospheric-corrosion-resistant steel grade Q390qNH is added (see Table 5);

g) The corrosion resistance requirements for atmospheric-corrosion-resistant steel and the maximum molybdenum (Mo) content limit for grades Q345qNH and Q370qNH are revised (see Table 5; Table 5 of the 2015 edition).

h) The requirements for carbon equivalent are revised (see Table 6; Table 6 of the 2015 edition);

i) The requirements for welding crack susceptibility index of thermomechanically rolled steel are revised (see Table 7; Table 7 of the 2015 edition);

j) The requirements for crack susceptibility index of atmospheric-corrosion-resistant steel are added (see Table 8);

k) Delivery conditions are revised (see 6.2; 7.3 of the 2015 edition);

l) Mechanical property requirements for grades Q390q and Q390qNH are added (see Table 9 and Table 10);

m) Yield strength values for grades Q370q(NH) to Q500q(NH) with thickness over 100 mm are supplemented (see Table 9);

n) The tensile strength requirements for all steel grades are revised to be graded by thickness (see Table 9; Table 8 of the 2015 edition);

o) The requirements for impact absorbed energy are revised (see Table 10; Table 8 of the 2015 edition);

p) The requirements for yield-to-tensile strength ratio of steel are revised (see 7.7 and Annex C; 7.4.6 and Annex B of the 2015 edition);

q) The guideline for evaluating atmospheric corrosion resistance of weathering bridge steel is deleted (see Annex C of the 2015 edition);

r) Reference service environments of bridge sites where atmospheric-corrosion-resistant steel can be applied without coating are added (see Annex A);

s) Recommended ordering standards for other types of bridge steel are added.

1 Scope

This Document specifies the designation method, ordering details, manufacturing process, technical requirements, test methods, inspection rules, packaging, marking, and quality certificate of structural steel for bridge.

This Document applies to single-rolled steel plates for bridge structural steel with a thickness not exceeding 150 mm, and hot-rolled steel strips and sheared steel plates for bridge structural steel with a thickness not exceeding 25.4 mm (hereinafter referred to as steel plates and strips).

2 Normative References

The provisions in following documents become the essential provisions of this Document through reference in this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document.

GB/T 222 Permissible tolerances for chemical composition of steel products

GB/T 223 (all parts) Iron, steel and alloy – Methods for chemical analysis

GB/T 228.1 Metallic materials - Tensile testing - Part 1.Method of test at room temperature

GB/T 229 Metallic materials - Charpy pendulum impact test method

GB/T 232 Metallic materials - Bend testing method

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 & expression and judgement of limiting values

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 20124 Steel and iron - Determination of nitrogen content - Thermal conductimetric method after fusion in a current of inert gas (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 Normalizing

A heat treatment process in which steel is heated to a suitable temperature above the phase transformation point and then cooled in air to a temperature below certain phase transformation point.

3.2 Thermomechanical rolling

It is a rolling process in which the final deformation of steel is carried out within a certain temperature range, thereby ensuring that the steel acquires properties that cannot be obtained through heat treatment alone.

NOTE 1.Thermomechanical rolling includes the process of increasing the cooling rate in tempered or non-tempered conditions. Tempering includes self-tempering but excludes direct quenching and quenching followed by tempering.

NOTE 2.Also known as TMCP (Thermomechanical Controlled Process), and in some publications as "controlled rolling".

3.3 Quenched and tempered

The heat treatment method involves quenching the steel and then tempering it at high temperature.

3.4 Atmospheric corrosion resisting steel

Steel that adds certain alloying elements, such as Cr, Ni, Cu, and Mo, and improves its atmospheric corrosion resistance by forming a dense rust layer on the metal matrix surface.

NOTE 1.Atmospheric corrosion resisting steel is also called weathering steel, code. NH.

NOTE 2.For bridge site reference environments for uncoated applications of atmospheric corrosion resisting steel, see Appendix A.

4 Designation Method

The steel designation consists of four parts. the first letter of the pinyin (Qu) for "yield strength", the specified minimum yield strength value, the first letter of the pinyin (qiao) for "bridge", and the quality grade symbol.

NOTE 1.Q + specified minimum yield strength value + q, abbreviated as steel grade.

EXAMPLE 1.Q420qD.

Where.

Q - the first letter of the pinyin (Qu) for "yield strength";

420 - the specified minimum yield strength value, in MPa;

q - the first letter of the pinyin (qiao) for "bridge";

D - quality grade D.

Bridge steel with weathering resistance properties is designated by adding "weathering" (NH) after the above-mentioned designation.

NOTE 2.Q + specified minimum yield strength value + q + NH, also abbreviated as steel grade.

EXAMPLE 2.Q420qDNH.

NH - the first letter of the pinyin (Nai Hou) for "weathering".

When thickness-direction properties are required for steel plates, a symbol representing the thickness-direction (Z-direction) property level (Z15, Z25, Z35) shall be added after the designations specified above, such as Q420qDZ35, Q420qDNHZ35.

5 Ordering Details

Contracts or orders placed according to this Document shall include at least the following.

a) This Document number;

b) Product name;

c) Designation;

d) Specification;

e) Dimensions, shape, and precision requirements;

f) Weight (quantity);

g) Delivery condition;

h) Special requirements.

6 Manufacturing Process

6.1 Smelting method

Steel is smelted in a converter or electric furnace and subjected to ladle refining treatments such as vacuum degassing.

6.2 Delivery condition

Steel shall be delivered in thermomechanical rolling (TMCP), thermomechanical rolling (TMCP) + tempered, or quenched and tempered delivery condition, as indicated in the quality certificate. When the thickness of steel plates of Q345q and Q370q grades is greater than 100mm but no greater than 150mm, delivery in the normalizing condition can be agreed upon by both the supplier and the purchaser.

7 Technical Requirements

7.1 Designations and chemical composition

7.1.1 The designations and chemical compositions (smelting analysis) of steels in different delivery conditions shall conform to the provisions of Tables 1 to 5.For designation comparisons in relevant standards, please refer to Annex B.

Table 1 Requirements for Phosphorus, Sulfur, Boron and Hydrogen Contents of Steels of Each Quality Grade

Chemical composition (mass fraction) / %

Quality Grade	Pmax	S^amax	B^b,c,d,emax	H^bmax
C	0.030	0.025	0.0005	0.0002
D	0.025	0.015
E	0.020	0.010
F	0.015	0.006
^a Where through-thickness properties are required for steel plates, the sulfur (S) content of the steel shall comply with the provisions of GB/T 5313. ^b Residual elements boron (B) and hydrogen (H) in steel may be exempted from analysis if the supplier can guarantee compliance with the limits. ^c This limit does not apply to quenched and tempered steels with intentionally added boron; the boron content shall be analyzed and recorded on the quality certificate. ^d For thermomechanically rolled steels with carbon (C) content ≤ 0.10 %, the boron content shall not exceed 0.0014 %. ^e For atmospheric-corrosion-resistant steels with carbon (C) content ≤ 0.06 %, the boron content shall not exceed 0.0014 %.

Table 2 Chemical Composition of Normalized Steel

Chemical composition (mass fraction) / %

Steel Grade	Quality Grade	Cmax	Simax	Mn	Nb^a	V^a	Ti^a	Als^a,b	Cr/Ni/Cumax	Nmax
Q345q	C,D, E	0.18	0.55	0.90 ~ 1.60	0.005 ~ 0.060	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.30	0.0080
Q370q	C,D, E	0.18	0.55	1.00 ~ 1.60	0.005 ~ 0.060	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.30	0.0080
General Note Normalizing is only applicable to steel plates with thickness greater than 100 mm and not greater than 150 mm.
^a Aluminium (Al), niobium (Nb), vanadium (V) and titanium (Ti) may be added singly or in combination. When added singly, their contents shall comply with the values specified in this table. When added in combination, at least one alloy element shall reach the minimum limit specified in the table; there is no upper limit for other elements, on condition that Nb + V + Ti ≤ 0.22 %. ^b If total aluminium (Alt) content is used for calculation, the total aluminium (Alt) content shall be within the range of 0.015 % to 0.050 %.

Table 3 Chemical Composition of Thermomechanically Rolled Steel

Chemical composition (mass fraction) / %

Steel Grade	Quality Grade	C max	Si max	Mn^*	Nb^a	V^a	Ti^a	Als^a,b	Cr max	Ni max	Cu max	Mo max	N max
Q345q	C, D, E	0.14	0.55	0.80 ~ 1.60	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.30	0.30	0.30	-	0.0080
Q370q		0.14	0.55	0.80 ~ 1.60	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.30	0.30	0.30	-	0.0080
Q390q		0.14	0.55	0.80 ~ 1.60	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.30	0.30	0.30	-	0.0080
Q420q	D, E, F	0.11	0.55	0.80 ~ 1.70	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.50	0.30	0.30	0.20	0.0080
Q460q		0.11	0.55	0.80 ~ 1.70	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.50	0.30	0.30	0.25	0.0080
Q500q		0.11	0.55	0.80 ~ 1.70	0.010 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.80	0.70	0.30	0.30	0.0080
Q550q		0.11	0.50	0.80 ~ 1.70	0.005 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	1.00	1.20	0.55	0.60	0.0080
Q620q	D, E, F	0.11	0.50	0.80 ~ 1.70	0.005 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	1.00	1.20	0.55	0.60	0.0080
Q690q	D, E, F	0.11	0.50	0.80 ~ 1.70	0.005 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	1.00	1.20	0.55	0.60	0.0080
General Note The symbol "-" in this table indicates not applicable.
Footnotes ^* Subject to mutual agreement between the supplier and purchaser, the maximum manganese (Mn) content may be up to 2.00 %. ^a Aluminium (Al), niobium (Nb), vanadium (V) and titanium (Ti) can be added singly or in combination. When added singly, their contents shall comply with the limits specified in this table. When added in combination, at least one alloy element shall reach the minimum limit specified in the table, with no restriction on upper limits for other elements, provided that Nb + V + Ti ≤ 0.22 %. ^b If calculation is based on total aluminium (Alt) content, the total aluminium (Alt) content shall be 0.015 % ~ 0.050 %.

Table 4 Chemical Composition of Quenched and Tempered Steel

Chemical composition* (mass fraction) / %

Steel Grade	Quality Grade	C max	Si max	Mn	Nb^b	V^b	Ti^b	Als^b,c	Cr	Ni	Cu	Mo	N max
Q600q	D, E, F	0.11	0.55	0.80 ~ 1.70	0.005 ~ 0.060	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	≤0.80	≤0.70	≤0.30	≤0.30	≤0.0080
Q650q	D, E, F	0.12	0.55	0.80 ~ 1.70	0.005 ~ 0.060	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	≤0.80	≤0.70	≤0.30	≤0.30	≤0.0080
Q620q	D, E, F	0.14	0.55	0.80 ~ 1.70	0.005 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.40 ~ 0.80	0.25 ~ 1.00	0.15 ~ 0.55	0.20 ~ 0.50	≤0.0080
Q690q	D, E, F	0.15	0.55	0.80 ~ 1.70	0.005 ~ 0.090	0.010 ~ 0.080	0.006 ~ 0.030	0.010 ~ 0.045	0.40 ~ 1.00	0.25 ~ 1.20	0.15 ~ 0.55	0.20 ~ 0.60	≤0.0080
Footnotes ^a Boron (B) element may be added in the range of 0.0005 % ~ 0.0030 %. ^b Aluminium (Al), niobium (Nb), vanadium (V) and titanium (Ti) may be added singly or in combination. When added singly, their contents shall comply with the limits specified in this table. When added in combination, at least one alloy element shall reach the minimum limit specified in the table, with no restriction on upper limits for other elements, provided that Nb + V + Ti ≤ 0.22 %. ^c If calculation is based on total aluminium (Alt) content, the total aluminium (Alt) content shall be 0.015 % ~ 0.050 %.

Table 5 Chemical Composition of Atmospheric-Corrosion-Resistant Steel

Chemical composition ^a,b,c,d,e (mass fraction) / %

Steel Grade	Quality Grade	C max	Si	Mn^d	Nb	V	Ti	Cr	Ni	Cu	Mo max	N max	Als^e
Q345qNH	C, D, E	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.40 ~ 0.70	0.30 ~ 0.40	0.25 ~ 0.50	0.20	0.0080	0.015 ~ 0.050
Q370qNH	C, D, E	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.40 ~ 0.70	0.30 ~ 0.40	0.25 ~ 0.50	0.20	0.0080	0.015 ~ 0.050
Q390qNH	C, D, E	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.40 ~ 0.70	0.30 ~ 0.40	0.25 ~ 0.50	0.20	0.0080	0.015 ~ 0.050
Q420qNH	D, E, F	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.40 ~ 0.70	0.30 ~ 0.40	0.25 ~ 0.50	0.20	0.0080	0.015 ~ 0.050
Q460qNH	D, E, F	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.40 ~ 0.70	0.30 ~ 0.40	0.25 ~ 0.50	0.20	0.0080	0.015 ~ 0.050
Q500qNH	D, E, F	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.45 ~ 0.70	0.30 ~ 0.45	0.25 ~ 0.55	0.25	0.0080	0.015 ~ 0.050
Q550qNH	D, E, F	≤0.11	0.15 ~ 0.50	1.10 ~ 1.50	0.010 ~ 0.100	0.010 ~ 0.100	0.006 ~ 0.030	0.45 ~ 0.70	0.30 ~ 0.45	0.25 ~ 0.55	0.25	0.0080	0.015 ~ 0.050
^a Aluminium (Al), niobium (Nb), vanadium (V) and titanium (Ti) may be added singly or in combination. When added singly, their contents shall comply with the values specified in this table. When added in combination, at least one alloy element shall reach the minimum limit specified in the table, with no restriction on upper limits for other elements, provided that Nb + V + Ti ≤ 0.22 %. ^b Calcium (Ca) treatment shall be carried out to control the morphology of sulfide inclusions. ^c The atmospheric corrosion index I of weathering steel shall not be less than 6.0. The calculation formula for I is as follows: I =26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P) −7.29(%Cu)(%Ni)−9.10(%Ni)(%P)−33.39(%Cu) ² ^d When delivered in coil form, the minimum manganese (Mn) content may be reduced to 0.50 %. ^e If calculation is based on total aluminium (Alt) content, the total aluminium (Alt) content shall be within the range of 0.020 % ~ 0.055 %.

7.1.2 Weldability Evaluation of Each Steel Grade

7.1.2.1

For normalized steel, quenched and tempered steel, and thermomechanically rolled steel with carbon content greater than 0.12 %, the weldability of steel shall be evaluated by carbon equivalent (CEV). The carbon equivalent of each steel grade shall comply with the provisions of Table 6.

The carbon equivalent shall be calculated from ladle analysis by Formula (1):

CEV(%)=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15(1)

Table 6 Carbon Equivalent (CEV) of Normalized Steel, Quenched and Tempered Steel and Thermomechanically Rolled Steel with Carbon Content > 0.12 %

Category	Steel Grade	Carbon Equivalent (CEV) / %
		Nominal thickness(mm)
		≤50	>50 ~ 100	>100 ~ 130	>130 ~ 150
Normalized Steel	Q345q	-	-	Subject to agreement	Subject to agreement
Normalized Steel	Q370q	-	-	Subject to agreement	Subject to agreement
Thermomechanically Rolled Steel	Q345q	≤0.38	≤0.40	Subject to agreement	-
	Q370q	≤0.38	≤0.40	Subject to agreement	-
	Q390q	≤0.41	≤0.41	Subject to agreement	-
Quenched and Tempered Steel	Q500q	≤0.50	≤0.55	Subject to agreement	-
	Q550q	≤0.52	≤0.57	-	-
	Q620q	≤0.55	≤0.60	-	-
	Q690q	≤0.60	≤0.65	-	-
Note: The symbol "-" in this table means not applicable.

7.1.2.2

For atmospheric-corrosion-resistant steel and thermomechanically rolled steel with carbon content not greater than 0.12 %, the weld cracking susceptibility index (Pcm) shall be adopted instead of carbon equivalent to evaluate the weldability of steel. Pcm shall be calculated based on ladle analysis chemical composition in accordance with Formula (2), and its value shall comply with the provisions specified in Table 7 and Table 8.

Pcm(\%) = C+ Si/30 + Mn/20 +Cu/20 +Ni/60 +Cr/20 +Mo/15 +V/10 + 5B (2)

Table 7 Weld Cracking Susceptibility Index of Thermomechanically Rolled Steel

Category	Steel Grade	Weld Cracking Susceptibility Index (Pcm) / %
		Nominal thickness ≤50 mm	Nominal thickness >50 ~ 100 mm	Nominal thickness >100 ~ 130 mm	Nominal thickness >130 ~ 150 mm
Thermomechanically Rolled Steel	Q345q	≤0.20	≤0.20	≤0.20	-
	Q370q	≤0.20	≤0.20	≤0.20	-
	Q390q	≤0.21	≤0.21	≤0.21	-
	Q420q	≤0.22	≤0.22	≤0.22	-
	Q460q	≤0.22	≤0.23	≤0.23	-
	Q500q	≤0.23	≤0.25	≤0.25	-
	Q550q	≤0.23	≤0.25	-	-
	Q620q	≤0.24	≤0.25	-	-
	Q690q	≤0.24	≤0.25	-	-
Note: The symbol "-" in this table means not applicable.

Table 8 Weld Cracking Susceptibility Index of Atmospheric-Corrosion-Resistant Steel

Category	Steel Grade	Weld Cracking Susceptibility Index (Pcm) / %
		Nominal thickness ≤50 mm	Nominal thickness >50～100 mm	Nominal thickness >100～130 mm	Nominal thickness >130～150 mm
Atmospheric-Corrosion-Resistant Steel	Q345qNH	≤0.22	≤0.24	Subject to agreement	-
	Q370qNH	≤0.22	≤0.24		-
	Q390qNH	≤0.22	≤0.24		-
	Q420qNH	≤0.23	≤0.25		-
	Q460qNH	≤0.23	≤0.25		-
	Q500qNH	≤0.24	≤0.26		-
	Q550qNH	≤0.24	≤0.26		-
Note: The symbol "-" in this table means not applicable.

7.1.3

The permissible tolerances for the finished chemical composition of steel shall conform to GB/T 222.

7.2 Mechanical Properties

7.2.1

The mechanical properties of steel plates and strips shall comply with the provisions of Table 9 and Table 10.

7.2.2

The Charpy (V-notch) impact absorbed energy shall be calculated as the arithmetic mean value of a group of 3 test pieces. One individual value may be lower than the value specified in Table 10, but shall not be less than 70 % of the specified value.

Table 9 Tensile Test^a,b,c

Steel Grade	Quality Grade	Tensile Test^a,b,c
		Lower Yield Strength (R_eL) / MPa				Tensile Strength(R_eL) / MPa			Elongation after Fracture (A) / %
		Nominal thickness / mm				Nominal thickness / mm
		≤50	>50～100	>100～130	>130～150	≤100	>100～130	>130～150
		not less than
Q345q Q345qNH	C D E	345	335	305	305	490	430	430	20
Q370q Q370qNH	C D E	370	360	320	320	510	430	430	20
Q390q Q390qNH	C D E	390	380	335	-	520	450	-	20

Table 9 Tensile Properties (Continued)

Steel Grade	Quality Grade	Tensile Test^a,b,c
		Lower Yield Strength (R_eL) / MPa				Tensile Strength (R_eL) / MPa			Elongation after Fracture (A) / %
		Nominal thickness / mm				Nominal thickness / mm
		≤50	>50～100	>100～130	>130～150	≤100	>100～130	>130～150
		not less than
Q420qQ 420qNH	D E F	420	410	365	-	540	460	-	19
Q460q Q460qNH	D E F	460	450	385	-	570	490	-	18
Q500q Q500qNH	D E F	500	480	450	-	630	560	-	18
Q550q Q550qNH	D E F	550	530	-	-	660	-	-	16
Q620q	D E F	620	580	-	-	720	-	-	15
Q690q	D E F	690	650	-	-	770	-	-	14
Note: The symbol "-" in this table means not applicable.
Footnotes ^a When the yield phenomenon is not obvious, the proof strength of non-proportional extension R_p0.2may be used instead. ^b Transverse test pieces shall be taken for the tensile test. ^c Circular tensile specimens shall be adopted when the steel plate thickness is greater than 40 mm; circular tensile specimens may also be adopted when the steel plate thickness is greater than 25 mm and not greater than 40 mm if the testing capacity is insufficient.

Table 10 Impact Properties

Steel Grade	Quality Grade	Charpy (V-notch) Impact Test*
		Test Temperature / ℃	Absorbed Energy (KV₂) / J
			Nominal thickness / mm
			≤12	>12～100	>100～150
			not less than
Q345q Q345qNH	C	0	80	120	55
	D	−20	80	120	47
	E	−40	80	120	31
Q370q Q370qNH	C	0	80	120	55
	D	−20	80	120	47
	E	−40	80	120	31
Q390q Q390qNH	C	0	80	120	55
	D	−20	80	120	47
	E	−40	80	120	31
Q420q Q420qNH	D	−20	80	120	47
	E	−40	80	120	31
	F	−60	Subject to agreement	47	-
Q460q Q460qNH	D	−20	80	120	47
	E	−40	80	120	31
	F	−60	Subject to agreement	47	-
Q500q Q500qNH	D	−20	80	120	47
	E	−40	80	120	31
	F	−60	Subject to agreement	54	-
Q550q Q550qNH	D	−20	80	120	-
	E	−40	80	120	-
	F	−60	Subject to agreement	60	-
Q620q	D	−20	80	120	-
	E	−40	80	120	-
	F	−60	Subject to agreement	69	-
Q690q	D	−20	80	120	-
	E	−40	80	120	-
	F	−60	Subject to agreement	77	-
Note: The symbol "-" in this table means not applicable.
*Longitudinal test pieces shall be taken for the impact test.

7.2.3

For steel plates with thickness less than 12 mm, small-size specimens shall be used for the Charpy (V-notch) impact test.

When the thickness is greater than 8 mm and not greater than 12 mm, the dimension of small-size specimens shall be 7.5 mm×10 mm×55 mm, and the test result shall not be less than 75 % of the value specified in Table 10.

When the thickness is 6 mm ~ 8 mm, the dimension of small-size specimens shall be 5 mm×10 mm×55 mm, and the test result shall not be less than 50 % of the value specified in Table 10. No impact test shall be performed for steel plates with thickness less than 6 mm.

7.2.4

If the impact test results fail to comply with the provisions of 7.2.2 and 7.2.3, another set of three specimens shall be taken from the same steel plate for retesting.

The arithmetic average of the six test results from the original test and retest shall not be lower than the specified value.

Two individual values are permitted to be lower than the specified value, but only one value shall be less than 70 % of the specified limit.

7.2.5

When through-thickness properties are required for steel plates, the through-thickness reduction of area shall conform to the requirements of the corresponding grade specified in GB/T 5313.

7.3 Technological Properties

The bend test for steel plates and strips shall comply with the provisions of Table 11.

The bend test may be waived if the supplier provides a written guarantee.

Table 11 Technological Properties

180° Bend Test
Nominal thickness / mm		Bend Requirement
≤16	＞16
D=2a	D=3a	No visually observable cracks shall appear on the outer surface of the specimen
Transverse test pieces shall be used for the bending test. Note: D = diameter of bending mandrel; a = thickness of the test piece.

7.4 Surface Quality

7.4.1

The surface of steel plates and strips shall be free from harmful defects including blowholes, scabs, cracks, laps, inclusions and rolled-in scale that impair service performance. No visually observable delamination is allowed.

7.4.2

Thin rolled-in scale, rust, slight surface roughness, net pattern marks, scratches and other minor local defects are permitted, provided that these defects do not interfere with surface inspection.

The depth of such defects shall not exceed half of the thickness tolerance of the steel plate or strip, and the minimum permissible thickness shall still be ensured.

7.4.3

Surface defects may be removed by grinding or other methods. The ground surface shall be smooth without sharp edges. The depth after grinding shall not exceed the lower deviation of plate thickness, and the minimum permissible thickness shall be maintained.

7.4.4

The length of defective sections on steel strips shall not exceed 6 % of the total length of each coil.

7.4.5

Subject to mutual agreement between the supplier and purchaser and specified in the contract, the surface quality of steel plates may comply with GB/T 14977.

7.5 Non-Destructive Testing

Single-rolled steel plates with thickness greater than 20 mm shall be ultrasonically inspected in accordance with GB/T 2970, with acceptance grade no less than Class Ⅱ.

For other single-rolled steel plates, non-destructive testing may also be carried out upon mutual agreement between both parties.

The inspection standard and acceptance grade shall be clearly stipulated in the contract or technical agreement.

7.6 Dimensions, Shape and Mass

7.6.1

The dimensions, shape, mass and permissible deviations of steel plates and strips shall comply with GB/T 709.

7.6.2

Subject to mutual agreement between both parties and stipulated in the contract, steel plates and strips with alternative dimensions, shapes and dimensional tolerances may be supplied.

7.7 Other Requirements

Upon mutual agreement between the supplier and purchaser and stipulated in the contract, requirements for the yield-to-tensile strength ratio may be specified for steel plates and strips. The recommended maximum yield-to-tensile strength ratio is 0.80.

See Annex C.

8 Test Methods

8.1

Chemical analysis of steel shall generally be carried out in accordance with GB/T 223 (all parts), GB/T 4336, GB/T 20123, GB/T 20124, GB/T 20125 or other common methods. In case of arbitration, the test method shall be agreed upon by both the supplier and the purchaser.

8.2

Inspection items and test methods for steel plates and strips shall comply with the provisions of Table 12.

Table 12 Inspection Items, Sampling Quantity, Sampling Method and Test Methods for Steel Plates and Strips

No.	Inspection Item	Sampling Quantity	Sampling Method	Test Method
1	Chemical composition (ladle analysis)	1 sample per heat	GB/T 20066	See 8.1
2	Tensile test	1 sample per batch	GB/T 2975	GB/T 228.1
3	Bend test	1 sample per batch	GB/T 2975	GB/T 232
4	Impact test	1 set (3 specimens) per batch	GB/T 2975	GB/T 229
5	Through-thickness property test	1 set (3 specimens) per batch	GB/T 5313	GB/T 5313
6	Non-destructive testing	Every plate	-	GB/T 2970
7	Surface quality	Every plate or every coil	-	Visual inspection and measurement
8	Dimensions and shape	Every plate or every coil	-	Suitable measuring tools

9 Inspection Rules

9.1 Inspection and Acceptance

Inspection and acceptance of steel products shall be conducted by the quality inspection department of the supplier.

9.2 Batch Division

9.2.1

Steel plates and strips shall be submitted for inspection by batch. Each batch shall consist of steel plates or strips of the same grade, same heat number, same specification, same rolling schedule and same heat treatment schedule. The mass of each batch shall not exceed 60 t. For rolled coils heavier than 30 t and sheared steel plates, two rolling coils may be grouped into one batch.

9.2.2

The batch size for through-thickness mechanical property tests shall comply with GB/T 5313.

9.3 Sampling Quantity and Sampling Method

The sampling quantity and sampling method for each batch of steel plates and strips shall comply with the provisions of Table 12.

9.4 Retest and Judgement Rules

9.4.1

Retest and judgement for tensile test, impact test and bend test shall comply with GB/T 17505.

9.4.2

Retest and judgement for the through-thickness reduction of area of Z-direction steel shall comply with GB/T 5313.

9.5 Rounding of Numerical Values

The test results for mechanical properties and chemical composition of steel plates and strips shall be rounded by the comparison method of rounded values, in accordance with the rounding rules specified in GB/T 8170.

10 Packaging, Marking and Quality Certificate

Packaging, marking and quality certificates for steel plates and strips shall comply with the provisions of GB/T 247.

11 Recommended Ordering Standards for Other Types of Bridge Steel

See Annex D for the recommended ordering standards for other types of bridge steel.

Annex A

(Informative)

Reference Service Environments for Bridge Sites Where Atmospheric-Corrosion-Resistant Steel Can Be Used Without Coating

A.1 Urban and Rural Atmospheric Environment

The urban and rural atmospheric environment includes rural atmosphere and urban atmosphere.

a) Rural atmosphere: Inland rural areas far away from cities and small towns without obvious corrosive contaminant pollution. The air is clean, basically free from industrial media and salt fog pollution.

b) Urban atmosphere: Heavily populated areas without concentrated industries and suburban areas with low-level pollution, slightly contaminated by industrial corrosive media.

Environmental characteristics of urban and rural atmosphere:

Annual average deposition rate of Cl^-: not greater than 3mg/m²▪d;

Annual average deposition rate of SO₂: not greater than 24mg/m²▪d;

Total annual wet time shall not exceed 5256 h (time with temperature above 0 ℃ and relative humidity higher than 80 %).

A.2 Coastal Atmospheric Environment

If the corrosion factors in the coastal atmospheric environment satisfy the environmental characteristics specified in A.1, atmospheric-corrosion-resistant steel may also be used without coating.

Annex B

(Informative)

Equivalent Grade Comparison Table for Relevant Standards

The grade comparison between this document and relevant foreign standards is shown in Table B.1.

Table B.1 Equivalent Grade Comparison Table for Relevant Standards

This Document	ASTM A709-21	EN 10025-3:2019	EN 10025-4:2019	EN 10025-6:2019
Q345q	50[345] 50W[345W] HPS 50W[HPS 345W]	S355N, S355NL	S355M, S355ML	-
Q370q	-	-	-	-
Q390q	-	-	-	-
Q420q	-	-	S420M, S420ML	-
Q460q	HPS 70W[HPS 485W]	-	S460M, S460ML	S460Q, S460QL, S460QL1
Q500q	-	-	S500M, S500ML	S500Q, S500QL, S500QL1
Q550q	-	-	-	S550Q, S550QL, S550QL1
Q620q	-	-	-	S620Q, S620QL, S620QL1
Q690q	HPS 100W[HPS 690W]	-	-	S690Q, S690QL, S690QL1
Note: The symbol "-" in this table means not applicable.

Annex C

(Informative)

Yield-to-Tensile Strength Ratio of Steel Products

For thermomechanically controlled processed (TMCP) steel and TMCP + tempered steel, the recommended yield-to-tensile strength ratios are given in Table C.1.

Table C.1 Recommended Yield-to-Tensile Strength Ratio of Steel

Steel Grade	Yield-to-Tensile Strength Ratio R_eL/R_m
	Nominal thickness
	≤12 mm	＞12 mm
Q345q, Q345qNH	0.88	0.85
Q370q, Q370qNH	0.88	0.85
Q390q, Q390qNH	0.88	0.85
Q420q, Q420qNH	0.88	0.86
Q460q, Q460qNH	0.88	0.86
Q500q, Q500qNH	0.88	0.86
^* When the yield phenomenon is not distinct, proof strength of non-proportional extension R_p0.2 may be substituted.

Annex D

(Informative)

Ordering Standards for Other Types of Bridge Steel

With the continuous advancement of bridge fabrication technology, new grades of bridge steel have been successively developed.

For example, bridge steel with marine atmospheric corrosion resistance and longitudinal variable thickness has been gradually applied in practical projects, and corresponding standards have been formulated.

Therefore, subject to the actual project requirements, the supplier and purchaser are advised to place orders with reference to T/CISA 073 and T/CISA 217.

References

[1] GB/T 14977, General requirements for surface quality of hot rolled steel plates

[2] T/CISA 073, Steel plates resistant to marine atmospheric corrosion for bridges

[3] T/CISA 217, Hot rolled longitudinally tapered steel plates for bridges

[4] ASTM A709-21, Standard specification for structural steel for bridges

[5] EN 10025-3:2019, Hot rolled products of structural steels - Part 3: Technical delivery conditions for normalized/normalized rolled weldable fine grain structural steels

[6] EN 10025-4:2019, Hot rolled products of structural steels - Part 4: Technical delivery conditions for thermomechanical rolled weldable fine grain structural steels

[7] EN 10025-6:2019, Hot rolled products of structural steels - Part 6: Technical delivery conditions for flat products of high yield strength structural steels in the quenched and tempered condition

GB/T 714-2025 Structural steel for bridge

1 Scope

2 Normative References

3 Terms and Definitions

3.1 Normalizing

3.2 Thermomechanical rolling

3.3 Quenched and tempered

3.4 Atmospheric corrosion resisting steel

4 Designation Method

5 Ordering Details

6 Manufacturing Process

6.1 Smelting method

6.2 Delivery condition

7 Technical Requirements

7.1 Designations and chemical composition

7.1.2 Weldability Evaluation of Each Steel Grade

7.1.2.1

7.1.2.2

7.1.3

7.2 Mechanical Properties

7.2.1

7.2.2

Table 10 Impact Properties

7.2.3

7.2.4

7.2.5

7.3 Technological Properties

7.4 Surface Quality

7.4.1

7.4.2

7.4.3

7.4.4

7.4.5

7.5 Non-Destructive Testing

7.6 Dimensions, Shape and Mass

7.6.1

7.6.2

7.7 Other Requirements

8 Test Methods

8.1

8.2

9 Inspection Rules

9.1 Inspection and Acceptance

9.2 Batch Division

9.2.1

9.2.2

9.3 Sampling Quantity and Sampling Method

9.4 Retest and Judgement Rules

9.4.1

9.4.2

9.5 Rounding of Numerical Values

10 Packaging, Marking and Quality Certificate

11 Recommended Ordering Standards for Other Types of Bridge Steel

Annex A

A.1 Urban and Rural Atmospheric Environment

A.2 Coastal Atmospheric Environment

Annex B

Annex C

Annex D

References