GB/T 25052-2010 English PDF (GBT25052-2010)

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GB/T 25052-2010: Continuously hot-dip coated steel sheet and strip -- Tolerances on dimensions, shape and weight
GB/T 25052-2010
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.50
H 46
Continuously hot-dip coated steel sheet and strip -
Tolerances on dimensions, shape and weight
ISSUED ON. SEPTEMBER 2, 2010
IMPLEMENTED ON. JUNE 1, 2011
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword... 3
1 Scope... 4
2 Normative references... 4
3 Classifications and codes... 4
4 Dimensions, shapes, and tolerances... 5
5 Weights... 10
6 Measurement of dimensions and shapes... 11
7 Rounding of numerical values... 12
Continuously hot-dip coated steel sheet and strip -
Tolerances on dimensions, shape and weight
1 Scope
This standard specifies the dimensions, shapes, weights, and tolerances of continuously
hot-dip coated steel sheets and strips.
This standard is applicable to continuously hot-dip coated wide steel strips with a
thickness of not more than 6.5 mm and their original steel sheets (hereinafter referred
to as steel sheets) and longitudinally cut steel strips.
Note. Thickness refers to the final product thickness including plating.
2 Normative references
The following documents are essential to the application of 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 standard.
GB/T 8170 Rules of rounding off for numerical values and expression and judgment
of limiting values
3 Classifications and codes
3.1 According to dimensional precision, steel sheets and strips are classified into.
Ordinary thickness precision PT. A
Advanced thickness precision PT. B
Ordinary width precision PW. A
Advanced width precision PW. B
Ordinary length precision PL. A
Advanced length precision PL. B
3.2 According to roughness precision, steel sheets and strips are classified into.
5 Weights
Steel sheets are delivered by theoretical or actual weights, and steel strips are delivered
by actual weights.
5.1 When a steel sheet is delivered by the theoretical weight, the theoretical weight shall
be calculated by the nominal sizes.
5.2 Weight calculation method for theoretical weights
5.2.1 Calculation method of the nominal thickness of a coating
Nominal coating thickness = [sum of the nominal weights of two-sided coatings
(g/m2)/50(g/m2)] × r × 10-3(mm)
r is the characteristic value of the coating material, such as the characteristic value of
zinc, zinc-iron alloy coating is 7.1, and the density coefficient of aluminum-zinc (55%
Al) coating is 13.3.
5.2.2 The weight calculation method for the theoretical weight of a steel sheet shall be
as specified in Table 10.
6 Measurement of dimensions and shapes
6.1 Thickness
The thickness shall be measured at a distance of not less than 40 mm from the edge.
6.2 Width
The width shall be measured perpendicularly to the steel sheet or the centerline of the
steel sheet.
6.3 Length
The length shall be measured parallelly to the longitudinal axis of the product.
6.4 Roughness
The maximum distance without contact between the steel sheet and a flat horizontal
surface is the roughness tolerance, as shown in Figure 1.
6.5 Bevel cut
The bevel cut is the vertical projection length of the width-direction side of the steel
sheet to the edge in the rolling direction, or half of the difference between the diagonals
of the steel sheet, as shown in Figure 2.