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2020年6月22日

了解无损检测结果

苏格兰人打造 reviews the numerous applications in forgings and the different 测试的方法.

Forging is one of the oldest skills known to man and it’s tough to envision manufacturing and even life without the parts created by forging. 的一些 申请锻件 可以直截了当,比如 用于齿轮和法兰或 酒吧 船舶轴. 与此形成鲜明对比的是, 其他的则非常复杂, such as hollows for oil country tubular goods (OCTG) and pressure tubing for power boilers or domes for nuclear waste storage.

There are numerous 申请锻件. As a result, there are many manufacturing and testing standards that forgings must meet. Forgings are commonly created to the standards of the following organizations:

  • •  AISI - American Iron and Steel Institute
  • • ANSI - American National Standards Institute
  • AMS -航空材料标准
  • •API -美国石油学会
  • • ASTM - American Society for 测试 and Materials
  • • ASME - American Society of Mechanical Engineers
  • •NAVSEA -海军海上系统司令部
  • •DIN EN -欧洲国家标准

And, just like the applications of the forgings, the 测试的方法 可以多种多样. 例如, testing from a ring to a tube for a critical, high-pressure use is not as simple as it first appears. Numerous standards could apply; it depends on the application. ASTM A668, for example, references six different standards.

  1. A275/A275M Practice for Magnetic Particle Examination of Steel Forgings
  2. A370 Test Methods and Definitions for Mechanical 测试 of Steel Products
  3. A388/A388M Practice for Ultrasonic Examination of Steel Forgings
  4. A788/A788M Specification for Steel Forgings, 一般 Requirements
  5. E290 Test Methods for Bend 测试 of Material for Ductility
  6. E340 Practice for Macroetching Metals and Alloys

Each standard specifies procedures for measurements or test methods. 就材料标准而言, the mill typically calls out the capabilities of material based on sound forging practices. There are many tests available to meet criteria standards and ensure part quality that helps find indications, 或不完美, in the material – magnetic particle test (MT), dye penetrant test (PT) and ultrasonic inspection (UT).

MT and PT discover surface flaws; they are relatively easy and inexpensive. MT uses a magnetic field with a solution containing iron filing particles that highlight an indication in the forging as the iron particles collect at the magnetic flux that leaks from a crack or void. PT can be more time consuming as it requires applying a liquid penetrant to the forging and then removing it; a developer must then sit on the piece to draw out remaining penetrant from any cracks or crevices. UT is a volumetric test and uses sound waves to find gaps in the forging; when the sound wave hits a void, it ends back a spike in the ultrasonic display, 这就是所谓的指示. All these methods require a finished surface to allow for accurate readings.

执行测试是一个过程, but evaluating a forging to determine if it is acceptable is a different process altogether. 例如, it’s not uncommon to require a UT inspection by requesting “UT per ASTM A388.“问题, 在本文档中详细说明, is that “this practice is intended for application to forgings, 有各种尺寸, 形状, 作文, 融化的过程, 和应用程序. 它是, 因此, impracticable to specify an ultrasonic quality level which would be universally applicable to such a diversity of products.” The standard does not list exact acceptance requirements other than indications that cannot exceed an acceptable size.

Since metal transitions from a liquid to a solid, there are always some particles that get trapped, 就像冰中的气泡或灰尘一样. While most particles get eliminated during the forging process, 一些可以保持在可接受的水平. So, this is why it is essential to discuss acceptance criteria, list the voids or flaws that might be found as well as the limits or extent that they are permitted. A good example is specifying the amount of non-metallic inclusions that may be permitted. The specification would include the sizes and spacing between non-metallic inclusions that must be measured and evaluated, which helps set expectations for both the customer and the manufacturer. 它是 important to note that there are ways to reduce the risk of indications in a forging, such as using refined material like Vacuum Arc Remelt (VAR), but increased purity results in increased cost. 

Finding the balance between acceptable quality and cost-effectiveness is often tricky. Not to mention how the acceptance criteria vary by each forged product. So, it is essential to carefully review documents that support the requirements of the end-use application. 从简单到复杂, a partner like the 苏格兰人打造 employee-owners can help guide you through this process.