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GB/T 709-2019 (GB/T709-2019)

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GB/T 709-2019: PDF in English (GBT 709-2019)

GB/T 709-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.50
H 46
Replacing GB/T 709-2006
Dimension, shape, weight and tolerance
for hot-rolled steel strip, plate and sheet
ISSUED ON: MARCH 25, 2019
IMPLEMENTED ON: FEBRUARY 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Classification and code ... 6
5 Dimensions ... 6
6 Dimension tolerances ... 7
7 Shape ... 13
8 Measurement of dimensions and shape ... 17
9 Weight ... 20
10 Rounding off of numerical values ... 21
Annex A (informative) Thickness tolerance of plates ... 22
Dimension, shape, weight and tolerance
for hot-rolled steel strip, plate and sheet
1 Scope
This Standard specifies terms and definitions, classification and code,
dimensions, dimension tolerances, shape, measurement of dimensions and
shape of hot-rolled steel plates/sheets and strips.
This Standard applies to plates with a rolling width of not less than 600 mm
(hereinafter referred to plates), wide strips, slit wide strips, and plates/sheets
cut from strips.
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 8170 Rules of rounding off for numerical values & expression and
judgement of limiting values
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
plate
Hot-rolled flat steel that is directly rolled and does not have fixed edge
deformation.
3.2
wide strip
Steel strips with a width of not less than 600 mm and delivered in rolls.
3.3
slit wide strip
Steel strips that are slit from wide strips and delivered in rolls.
3.4
plate/sheet cut from strip
Steel plates/sheets that are cut from wide strips or slit wide strips and delivered
in plates/sheets.
4 Classification and code
4.1 Classification according to edge state is as follows:
a) cut-edge, EC;
b) mill-edge, EM.
4.2 Classification according to thickness tolerance classes and code are as
follows:
a) Class N tolerance: the upper tolerance and the lower tolerance are equal;
b) Class A tolerance: the lower tolerance is specified according to the
nominal thickness;
c) Class B tolerance: the fixed lower tolerance is -0.30 mm;
d) Class C tolerance: the fixed lower tolerance is 0.00 mm.
4.3 Classification according to precision of thickness and code are as follows:
a) general precision of thickness, PT.A;
b) higher precision of thickness, PT.B.
4.4 Classification according to precision of flatness and code are as follows:
a) general precision of flatness, PF.A;
b) higher precision of flatness, PF.B.
5 Dimensions
5.1 Nominal dimension range
Table 2 (Class N).
6.1.1.2 As required by the demand party, and indicating the tolerance class in
the contract, it may supply plates with other tolerance classes and with
tolerance values equal to the tolerance values specified in Table 2, such as
Class A, Class B and Class C tolerances. It may also supply plates of which the
upper tolerance is limited and the tolerance values are equal to the tolerance
values specified in Table 2. The upper and lower tolerances are agreed upon
between the supply and demand parties.
6.1.1.3 For steel plates/sheets with a thickness greater than 200 mm, the
thickness tolerance may also be agreed upon between the supply and demand
parties and specified in the contract.
6.1.1.4 Agreed upon between the supply and demand parties, it may also
supply in accordance with the tolerances given in Annex A.
6.1.2 Thickness tolerance of steel strips (including plates/sheets cut from
strips)
6.1.2.1 The thickness tolerance of steel strips (including plates/sheets cut from
strips), of which the specified minimum yield strength Re is less than 360 MPa,
shall comply with the requirements of Table 3. If the demand party requires
supply according to the higher precision of thickness (PT.B), it shall be indicated
in the contract. If not indicated, supply according to the general precision of
thickness (PT.A). According to the requirements of the demand party, the upper
and lower deviations of steel strips may be adjusted within the tolerances
specified in Table 3.
6.1.2.2 The thickness tolerance of steel strips (including plates/sheets cut from
strips), of which the specified minimum yield strength Re is not less than 360
MPa, shall comply with the requirements of Table 4. If the demand party
requires supply according to the higher precision of thickness (PT.B), it shall be
indicated in the contract. If not indicated, supply according to the general
precision of thickness (PT.A). According to the requirements of the demand
party, the upper and lower deviations of steel strips may be adjusted within the
tolerances specified in Table 4.
6.1.2.3 When the yield strength is not specified in the product standard and the
thickness tolerance is not specified, the thickness tolerance of steel strips
(including plates/sheets cut from strips) shall be agreed upon between the
supply and demand parties and indicated in the contract.
7.1.1.1.2 The flatness shall be determined by measuring the maximum distance
between the upper surface of the plate and the ruler. If the wave spacing (the
distance between the two contact points of the ruler and the plate) is not more
than 1000 mm, use a 1000 mm long ruler. For longer wave spacing, use a 2000
mm long ruler. For flatness with a height of no more than 2 mm, it shall not be
regarded as a wave.
7.1.1.2 Technical requirements
7.1.1.2.1 The flatness of plates shall comply with the requirements of Table 10.
If the demand party requires supply according to the higher precision of flatness
(PF.B), it shall be indicated in the contract. If not indicated, supply according to
the general precision of flatness (PF.A).
7.1.1.2.2 When the wave spacing (the distance between the two contact points
of the ruler and the plate) is between 300 mm and 1000 mm, the maximum
flatness of the plate shall also comply with the following requirements:
a) General precision of flatness (PF.A): the maximum flatness of steel type L
is 1.0 % of the wave spacing, and the maximum flatness of steel type H
is 1.5 % of the wave spacing, both of which shall not exceed those
specified in Table 10;
b) Higher precision of flatness (PF.B): the maximum flatness of steel type L
is 0.5 % of the wave spacing, and the maximum flatness of steel type H
is 1.0 % of the wave spacing, both of which shall not exceed those
specified in Table 10.
Table 10 -- Flatness of plates
Dimensions in millimeters
7.1.2 Plates/sheets cut from strips
Nominal
thickness
Flatness
Steel type L Steel type H
Measurement length
Agreed upon
Table 13 -- Height of tower shape
Dimensions in millimeters
8 Measurement of dimensions and shape
8.1 Length that is not assessed
When inspecting the thickness and width of mill-edge steel strips without cutting
the head and tail, the total length L of the two ends that is not assessed is
90/nominal thickness (L is in mm, the nominal thickness is in mm) and shall be
no more than 20 m.
8.2 Thickness
For cut-edge steel strips (including plates/sheets cut from strips), it is measured
at a distance of not less than 25 mm from the longitudinal side. For mill-edge
steel strips (including plates/sheets cut from strips), it is measured at a distance
of not less than 40 mm from the longitudinal side. For cut-edge plates, it is
measured at a distance of not less than 25 mm from the edge (longitudinal and
transverse sides). The measurement site of mill-edge plates is agreed upon
between the supply and demand parties.
8.3 Width
The width shall be measured at where perpendicular to the centerline of steel
plates/sheets or strips.
8.4 Length
The length of the largest rectangle in steel plates/sheets.
8.5 Flatness
8.5.1 Place the steel plate/sheet freely on a flat surface without applying any
pressure other than the weight of the steel plate/sheet itself.
8.5.2 Use a ruler with a length of 1000 mm or 2000 mm, in any direction within
a region of at least 25 mm from the longitudinal side and at least 200 mm or
100 mm from the lateral side of the plate, measure the maximum distance
between the upper surface of the plate and the ruler, see Figure 1.
Nominal width Cut-edge
Height of tower shape
Mill-edge
9.2 When steel plates/sheets are delivered according to theoretical weight, the
theoretical weight is calculated using nominal dimensions and the carbon steel
density of 7.85 kg/dm3. Other steel grades are weighted according to the
corresponding standards.
9.3 When the thickness tolerance of steel plates/sheets is limited to negative or
positive tolerance, the thickness used for the theoretical weight is the average
value of the maximum thickness and the minimum thickness allowed.
9.4 The theoretical weight of steel plates/sheets is calculated according to the
calculation method specified in Table 14.
Table 14 -- Calculation method for
theoretical weight of steel plates/sheets
Calculation sequence Calculation method Rounding off of results
Basic weight/kg/(mm • m2) 7.85 (weight of 1 mm thickness and 1 m2 area)
Unit weight/kg/m2 Basic weight [kg/(mm • m
2)] × thickness
(mm)
Rounded off to 4 significant
figures
Area of steel plate/sheet/m2 Width (m) × length (m) Rounded off to 4 significant figures
Weight of a steel
plate/sheet/kg Unit weight (kg/m
2) × area (m2)
Rounded off to 3 significant
figures; rounded off to integer
value of kg when it exceeds 1000
kg
Total weight/kg Sum of the weights of steel plates/sheets Integer value of kg
10 Rounding off of numerical values
The measurement results are rounded off according to the rounded off value
comparison method. Rules of rounding off are implemented in accordance with
the provisions of GB/T 8170.
......
 
(Above excerpt was released on 2014-04-20, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT709-2019