GB/T 39428-2020 in English

《GB/T 39428-2020砂型铸钢件 表面质量目视检测方法》由TC54（全国铸造标准化技术委员会）归口，TC54SC1（全国铸造标准化技术委员会铸钢分会）执行，主管部门为国家标准化管理委员会。

Steel castings by sand casting - Visual examination method of surface quality

1 Scope

This standard specifies the visual examination method and quality grade of the surface quality of steel castings by sand casting.

This standard is applicable to steel castings by sand casting.

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 5611 Foundry terminology

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 5611 and the following apply.

3.1
photo comparator
a set of photos used to compare and evaluate the different surface appearances and surface discontinuities of the castings under examination

4 Examination methods

4.1 Personnel qualification

4.1.1 Inspectors shall be able to carry out visual examination.

4.1.2 Inspectors shall accept visual examination every year, of which the results need to meet the following requirements:

a) near vision acuity shall permit reading a minimum of Jaeger number 1 or Times Roman N 4.5 or equivalent letters (having a height of 1.6mm) at not less than 30cm with one or both eyes;

b) color vision shall be sufficient that the inspector can distinguish and differentiate contrast between the colors or shades of gray used in the examination.
4.2 Surface conditions

The surface under examination shall be clean and free of any substances that affect visual examination. Before visual examination, castings shall be subjected to surface cleaning treatments of sand blasting, shot blasting, etc.

4.3 Observation conditions

The visual examination shall be carried out under the illumination not less than 1,000lx. Under certain conditions, portable light may also be used to assist lighting.

4.4 Operating methods

4.4.1 During visual examination, the distance between the eye and the casting to be examined shall be less than 600mm, and the angle between the view and the plane to be examined shall not be less than 30°.

4.4.2 Examination tools such as square ruler, tape measure and cardboard may be used to examine a large plane. When the examination place is not conducive to direct observation, optical auxiliary instrument with a magnification of not more than 1 times may be used for examination.

4.4.3 The surface roughness and surface discontinuity of castings shall be compared and evaluated with reference to the photo comparators in Annex C.

5 Examination results

5.1 Photo comparator

5.1.1 Table 1 presents five surface quality defect types of castings, and each defect includes different levels. Refer to Annex C for photo comparators of each defect level.

5.1.2 The photo comparators are photo examples of actual dimensions of any 110mm×150mm area on the specified casting surface, which are used for evaluation of the same area of the casting surface.

5.2 Comparison results

Table 2 presents the level of alternative surface appearance and surface discontinuity.

Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Examination methods
5 Examination results
6 Inspection report
Annex A (Informative) Comparison between this standard and ISO 11971:2020 in clause/subclause number
Annex B (Informative) Technical differences between this standard and ISO 11971:2020 and their justifications
Annex C (Informative) Photo comparators of surface appearance and surface discontinuity