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GB/T 19418-2003 (GB/T19418-2003, GBT 19418-2003, GBT19418-2003) & related versions
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GB/T 19418-2003: PDF in English (GBT 19418-2003)
GB/T 19418-2003
ICS 25.160.50
J 33
GB/T 19418-2003 / ISO 5817.1992
Arc-welded joints in steel –
Guidance on quality levels for imperfections
(ISO 5817.1992, IDT)
Issued by. General Administration of Quality Supervision, Inspection and
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 5 
4 Symbols... 6 
5 Evaluation of welds ... 6 
Annex A ... 18 
This Standard is identical to international standard ISO 5817.1992 “Arc-welded
joints in steel - Guidance on quality levels for imperfections”.
Annex A of this Standard is informative.
This Standard was proposed by China Machinery Industry Federation.
This Standard shall be under the jurisdiction of National Technical Committee
on Welding of Standardization Administration of China.
The drafting organization of this Standard. Harbin Welding Institute.
Main drafter of this Standard. Piao Dongguang.
Arc-welded joints in steel - Guidance on quality
levels for imperfections
1 Scope
This Standard provides guidance on levels of imperfections in arc-welded joints
in steel. The levels refer to production quality and not to the fitness-for-purpose
(see 3.1) of the product manufactured.
This Standard applies to
- the following welding processes and their defined sub-processes in
accordance with GB/T 5185.
11 metal-arc welding without gas protection;
12 submerged-arc welding;
13 gas-shielded metal-arc welding;
14 gas-shielded welding with non-consumable electrode;
15 plasma arc welding;
- manual, mechanized and automatic processes;
- all welding positions;
- butt welds, fillet welds and branch connections;
- materials in the thickness range 3 mm to 63 mm.
Metallurgical aspects, e.g. grain size, hardness, are not covered by this
2 Normative references
The following standards contain the provisions which, through reference in this
Standard, constitute the provisions of this Standard. For dated references,
subsequent amendments (excluding corrections) or revisions do not apply to
this Standard. However, the parties who enter into agreement based on this
Standard are encouraged to investigate whether the latest versions of these
documents are applicable. For undated reference documents, the latest
versions apply to this Standard.
GB/T 324 Weld symbolic representation on drawings (eqv ISO 2553)
GB/T 3375 Welding terminology
GB/T 5185 Welding and allied processes - Nomenclature of processes and
reference numbers (eqv ISO 4063)
GB/T 6417 Classification and explanation of imperfections in fusion welded
joints (eqv ISO 6520)
3 Terms and definitions
For the purposes of this Standard, the following terms and definitions apply.
3.1 fitness-for-purpose
a product is fit for its intended purpose when it functions satisfactorily in service
during its stipulated lifetime.
3.2 weld thickness
3.2.1 fillet weld thickness (nominal throat thickness), a
height of the largest isosceles triangle that can be inscribed in the weld section
3.2.2 butt weld thickness, s
minimum distance from the surface of the part to the bottom of the penetration,
which cannot be greater than the thickness of the thinner of the parts
3.3 short imperfection
one or more imperfections of total length not greater than 25 mm in any 100
mm length of the weld or a maximum of 25 % of the weld length for a weld
shorter than 100 mm
3.4 long imperfection
one or more imperfections of total length greater than 25 mm in any 100 mm
length of the weld or a minimum of 25 % of the weld length for a weld shorter
than 100 mm
3.5 projected area
Table 1 (continued)
No. Imperfection designation
GB/T 6417
reference Remarks
Limits for imperfections for quality levels
4 Localized
2013 The total pore area within the cluster should be summed and
calculated as a percentage of the greater of the two areas. an
envelope surrounding all the pores or a circle with a diameter
corresponding to the weld width.
The permitted porous area should be local. The possibility of
masking other imperfections should be taken into consideration.
The following conditions and limits for imperfections shall be
a) Maximum dimension of he summation of the projected or surface
crack area of the imperfection
8% 4%
b) Maximum dimension of a single pore for
- butt welds
- fillet welds
d ≤ 0.5 s
d ≤ 0.5 a
d ≤ 0.4 s
d ≤ 0.4 a
d ≤ 0.3 s
d ≤ 0.3 a
c) Maximum dimension for localized clustered porosity 4 mm 3 mm 2 mm
5 Elongated
Long imperfections for
- butt welds
- fillet welds
h ≤ 0.5 s
h ≤ 0.5 a
In any case, maximum dimension for elongated cavities,
2 mm
Annex A
Additional information and guidelines for use of this Standard
This Standard specifies requirements for three levels of acceptance for
imperfections in welded joints of steel for arc welding processes according to
the scope. It may be used - where applicable - for other fusion welding
processes or weld thicknesses.
Different parts are very often produced for different applications but to similar
requirements. The same requirements should, however, apply to identical parts
produced in different workshops to ensure that work is carried out using the
same criteria. The consistent application of this International Standard is one of
the fundamental cornerstones of a quality assurance system for use in the
production of welded structures.
Multiple imperfections show a theoretical possibility of superimposed individual
imperfections. In such a case the total summation of all permitted deviations
should be restricted by the stipulated values for the different quality levels.
However, the value of a single imperfection may exceed for a single pore.
This Standard may be used in conjunction with a catalogue of realistic
illustrations showing the size of the permissible imperfections for the various
acceptance levels by means of photographs showing the face and root side
and/or reproductions of radiographs and of photomacrographs showing the
cross-section of the weld. Reference Radiographs for Weld Imperfection
Assessment Based on ISO 5817 issued by International Institute of Welding
(IIW) is one of the catalogues that may be used with reference cards to assess
the various imperfections and may be employed when opinions differ as to the
permissible size of imperfections.

Standard ID GB/T 19418-2003 (GB/T19418-2003)
Description (Translated English) Arc-welded joints in steel-Guidance on quality levels for imperfections
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard J33
Classification of International Standard 25.160.50
Word Count Estimation 9,980
Date of Issue 2003-11-28
Date of Implementation 2004-06-01
Adopted Standard ISO 5817-1992; IDT
Drafting Organization Harbin Welding Institute
Administrative Organization China Machinery Industry Federation
Regulation (derived from) Chinese national standard approved by the announcement in 2004 No. 1 (No. 63 overall)
Proposing organization China Machinery Industry Federation
Issuing agency(ies) General Administration of Quality Supervision, Inspection and Quarantine of the People Republic of China
Summary This standard specifies: steel welding joints defects quality level. These grades and products and its applicability (see 3. 1) is independent manufacturing quality related.