\n| Position through the thickness<\/td>\n | Properties near the surface and at mid-thickness are not necessarily the same<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n For tests requiring specimens, the technical requirements should therefore define the sampling position and direction where these factors affect the purpose of the evaluation.<\/p>\n For example, if a component is loaded predominantly in a specific direction, the sampling direction should be considered in relation to that loading condition.<\/p>\n If not specified in advance, the supplier may take specimens according to the default conditions of the standard or production procedure. The results may still be valid, but they may not necessarily meet the plant’s specific evaluation purpose.<\/p>\n Sampling position and direction form part of the test conditions and should be defined before the results are used for comparison or acceptance inspection.<\/p>\n 5. Test temperature is essential when evaluating impact toughness<\/span><\/h2>\nFor impact testing according to EN ISO 148-1, the test temperature directly affects the result.<\/p>\n The same material can produce different absorbed energy values when tested at different temperatures.<\/p>\n When reading an impact test result, it is therefore necessary to identify:<\/p>\n \n- applicable test method<\/li>\n
- test temperature<\/li>\n
- sampling position and direction<\/li>\n
- reported result<\/li>\n<\/ul>\n
An impact toughness value without the corresponding test temperature does not provide enough information for proper evaluation or comparison.<\/p>\n This is particularly important when selecting materials for components that operate or are subjected to loading at low temperatures.<\/p>\n If the plant requires a result at a specified temperature, this requirement needs to be stated before the order is placed.<\/p>\n A result obtained at a different temperature should not automatically be used to conclude that the material meets the requirement at the actual operating temperature.<\/p>\n 6. Springback needs to be checked when bending high-strength steel<\/span><\/h2>\nDuring cold bending, steel tends to recover part of its deformation after the bending force is removed. This phenomenon is known as springback.<\/p>\n The amount of springback depends not only on the material properties but also on the actual bending machine setup, punch geometry and processing conditions.<\/p>\n With high-strength steel, springback can be greater than with conventional steel.<\/p>\n This means that achieving the same final angle may require adjustment of the initial bending angle to compensate for springback.<\/p>\n For example, when changing from a conventional steel grade to high-strength steel, the bending machine settings previously used should not automatically be retained.<\/p>\n A data sheet may provide reference values, but actual results still depend on the processing equipment.<\/p>\n A bending trial should therefore be performed on the actual machine that will be used to determine the appropriate settings rather than relying only on theoretical values.<\/p>\n 7. Ultrasonic inspection needs to be agreed at the ordering stage<\/span><\/h2>\nUltrasonic inspection according to EN 10160 is used to assess the internal soundness of steel plate within the scope of the method.<\/p>\n It is a non-destructive testing (NDT) method that can detect internal discontinuities that cannot be identified directly through surface inspection.<\/p>\n However, ultrasonic inspection is not a default requirement for every batch of steel plate.<\/p>\n If the plant requires ultrasonic inspection results, this requirement needs to be defined and agreed before the order is placed.<\/p>\n This is particularly important for components requiring a specified level of internal soundness, such as thick components, load-bearing components or components expected to contain multiple welds.<\/p>\n If the order does not specify this requirement, it should not be assumed that the supplier will provide ultrasonic inspection results.<\/p>\n If additional inspection is required after delivery, the test conditions, inspection scope and cost responsibility need to be reassessed according to the agreement between the parties.<\/p>\n 8. What should be considered when inspecting material quality in the workshop?<\/span><\/h2>\nNot every material property can be determined using portable instruments in the warehouse or fabrication workshop.<\/p>\n Some measurements can be performed directly on the material. Other tests require specialized equipment or laboratory facilities.<\/p>\n \n\n\n| Inspection item<\/th>\n | Can it be performed in the workshop?<\/th>\n | Conditions to consider<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Surface hardness<\/td>\n | Can be measured using suitable equipment<\/td>\n | Equipment error needs to be understood and the surface needs to be prepared<\/td>\n<\/tr>\n | \n| Thickness<\/td>\n | Can be measured directly using dimensional measuring tools<\/td>\n | Measurements should be taken at suitable positions; the inspection framework uses three points per plate<\/td>\n<\/tr>\n | \n| Surface and edges<\/td>\n | Can be inspected visually and with suitable tools<\/td>\n | Compare against the agreed surface and edge criteria<\/td>\n<\/tr>\n | \n| Yield strength, tensile strength and elongation<\/td>\n | Requires tensile testing equipment<\/td>\n | Define the standard, sampling position and sampling direction<\/td>\n<\/tr>\n | \n| Impact toughness<\/td>\n | Requires impact testing equipment<\/td>\n | Test temperature and specimen conditions need to be defined<\/td>\n<\/tr>\n | \n| Internal soundness by ultrasonic inspection<\/td>\n | Requires specialized ultrasonic equipment<\/td>\n | Perform according to the agreed standard and inspection scope<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n The fact that a property cannot be checked using a portable instrument does not mean that the plant cannot verify it.<\/p>\n The appropriate equipment, method, test conditions and responsible function simply need to be identified.<\/p>\n 8.1. Three common errors when measuring hardness in the workshop<\/span><\/h3>\nHardness results can be significantly affected by surface condition.<\/p>\n \n\n\n| Measurement error<\/th>\n | Potential effect<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Measuring on a primed surface<\/td>\n | The result may be lower than the actual hardness of the base material<\/td>\n<\/tr>\n | \n| Measuring on a surface that has not been prepared flat<\/td>\n | Results may vary between repeated measurements<\/td>\n<\/tr>\n | \n| Measuring on an area that has undergone cold deformation<\/td>\n | The measured value may be higher due to work hardening<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n These errors do not necessarily affect the result in the same direction.<\/p>\n For example, a coating may affect contact between the measuring device and the material, while a cold-deformed area may have a different hardness from the original material condition.<\/p>\n When an abnormal result is found, the surface condition and measurement conditions should therefore be checked before concluding that the material does not comply.<\/p>\n 8.2. Measurement error of portable instruments needs to be established before acceptance inspection<\/span><\/h3>\nPortable hardness testers may produce results that differ from standardized laboratory testing.<\/p>\n The difference depends on the type of equipment, conditions of use and measurement method.<\/p>\n Before using the result as the basis for an acceptance inspection decision, the following need to be identified:<\/p>\n \n- equipment used<\/li>\n
- measurement method<\/li>\n
- surface condition<\/li>\n
- associated measurement error or uncertainty<\/li>\n
- range within which the result can be used<\/li>\n<\/ul>\n
The inspection record should state the measuring equipment used rather than recording only a hardness value.<\/p>\n If equipment error and test conditions have not been established, portable measurements should be used for initial assessment rather than automatically replacing test results obtained using the agreed standard method.<\/p>\n 9. Responsibilities of the different functions<\/span><\/h2>\nMaterial quality inspection needs to be organized from the stage when technical requirements are defined through to the preparation and retention of measurement records.<\/p>\n \n\n\n| Task<\/th>\n | Responsible function<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Determine the required tests before ordering<\/td>\n | Quality department<\/td>\n<\/tr>\n | \n| Include sampling position, sampling direction and test-condition requirements in the order<\/td>\n | Procurement<\/td>\n<\/tr>\n | \n| Inspect material quality in the warehouse and workshop<\/td>\n | Quality department or warehouse, according to assigned responsibilities<\/td>\n<\/tr>\n | \n| Determine measurement error and conditions for using portable equipment<\/td>\n | Department or personnel performing the measurement<\/td>\n<\/tr>\n | \n| Perform tensile tests, impact tests and other specialized testing<\/td>\n | Laboratory or appropriate testing organization<\/td>\n<\/tr>\n | \n| Perform actual bending trials on fabrication equipment<\/td>\n | Fabrication workshop<\/td>\n<\/tr>\n | \n| File test results and measurement records by batch<\/td>\n | Quality department<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Among these activities, defining the required tests and test conditions before ordering is particularly important to ensure that the results obtained can be used for the intended purpose.<\/p>\n If a requirement is identified only after the material reaches the warehouse, the plant may need to arrange additional testing or may no longer be able to obtain specimens under the originally intended conditions.<\/p>\n 10. Notes on applying this knowledge<\/span><\/h2>\nFirst, destructive testing needs to be defined at the ordering stage when the plant requires test results from the actual batch at specific sampling positions and under specific conditions. After receiving the material, it cannot be assumed that the originally required data can still be generated.<\/p>\n Second, Brinell and Rockwell use different methods and measurement scales. When comparing materials, the same method and test conditions should be used where possible rather than relying on converted values unnecessarily.<\/p>\n Third, sampling position and direction can affect the result. These details need to be defined according to the applicable standard and the technical requirements of the application.<\/p>\n Fourth, springback during bending depends on both the material and the actual machine setup. For high-strength steel, bending trials should be performed on the actual fabrication equipment to determine suitable settings.<\/p>\n Fifth, portable measuring instruments have measurement error. Workshop measurements can support abnormality detection but should not automatically replace a standardized test required for acceptance inspection.<\/p>\n Sixth, the common hardness-measurement errors and their likely effects described in this article are based on workshop inspection experience and are not presented as a separate standard.<\/p>\n A test result is meaningful only when it is accompanied by the test method, test conditions and data source. Using the correct standard, defining the sampling position and recording the measuring equipment allow the quality department to compare material batches on the same basis while reducing disputes caused by differences in how the tests are performed.<\/p>\n <\/p>\n","protected":false},"featured_media":8784,"parent":9454,"menu_order":2,"template":"","meta":{"_acf_changed":false,"inline_featured_image":false},"danh-muc-kien-thuc":[273],"class_list":["post-9466","kien-thuc","type-kien-thuc","status-publish","has-post-thumbnail","hentry","danh-muc-kien-thuc-standards-certification-and-inspection"],"acf":[],"_links":{"self":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc\/9466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc"}],"about":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/types\/kien-thuc"}],"up":[{"embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc\/9454"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/media\/8784"}],"wp:attachment":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/media?parent=9466"}],"wp:term":[{"taxonomy":"danh-muc-kien-thuc","embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/danh-muc-kien-thuc?post=9466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | | |