奥氏体不锈钢焊缝中δ铁素体的存在会影响焊缝的强韧性、耐腐蚀性及焊接性,工程现场的焊接过程通常借助铁素体含量测定仪来控制δ铁素体的含量。
Chemical, energy and processing plants are often subjectto heat, aggressive media and high pressure. Thesecircumstances demand steel with high corrosion and acid resistance that are resilient even at high temperatures.If the ferrite content is too low, then the weldedmaterial is susceptible to hot-cracking, if the ferrite contentis too high, the toughness, ductility as well as thecorrosion resistance of the steel are reduced. For duplexsteel, a ferrite deficit in the area of the weld seam resultsin stress corrosion cracking and reduction in strength.
The FERITSCOPE FMP30 measures the ferrite content in austenitic and duplex steel according to the magnetic induction method. All magnetisable structure sections are measured i. e., in addition to deltaferrite also strain-induced martensite, for example, or other ferritic phases. It is suited for measurements according to the Basler- Standard and according to DIN EN ISO 17655. Areas of application are onsite measurements, e. g. of austenitic platings as well as weld seams in stainless steel pipes, containers, boilers or other products made of austenitic or duplex steel.
Duplex steel is used increasingly in the chemical and petrochemical industries, e. g., for boilers and pipelines. A ferrite deficit in the weld seam area leads to strength reduction, an excess ferrite content to a reduction in toughness and ductility. In particular when welding duplex steel, the ferrite content in the welding area can easily assume unfavourable values either due to unsuitable welding filler materials or through poor heat input or heat removal. Only an onsite measurement can provide the assurance that the processing did not change the optimum ferrite content in an unfavourable manner at the expense of mechanical or corrosion-resistance properties.
图为：焊缝中铁素体含量的测量
Simple and quick measurements
（简单快速地测量）
It is easy to measure the ferrite content accurately whenusing the FERITSCOPE FMP30. Upon probe placementon the surface of the specimen, the reading is displayedautomatically and stored in the instrument. The probecan also be placed onto hard to reach areas. For suchapplications, the instrument features an “external start”function to trigger the measurements with the push ofa button. This is ideal for measurements in pipes, boreholes or grooves.
Calibration / Standards
（校准/校准片）
To obtain comparable measurement results, the instrumentsmust be adjusted or calibrated using standards that can be traced to internationally recognised secondary standards. For this purpose, the IIW (International Institute of Welding, UK) developed secondary standards that have been determined by the TWI (The Welding Institute, UK) according to the method described in DIN EN ISO 8249 and ANSI/AWS A4.2. Helmut Fischer offers certified calibration standard sets that are traceable to the TWI secondary standards for corrective and master calibrations. The standards of the FISCHER calibration standard sets list in addition to the ferrite numbers FN also the % Fe values. Influences including the shape of the part to be measured (strong curvature, thickness of the ferrite-containing coating, etc.) can be taken into account through corrective calibrations with customer-specific calibration standards or through correction factors (included). The normalisation and corrective calibration are stored application-specific in the respective application memory of the instrument
Magnetic induction method
（测量原理）
The FERITSCOPE FMP30 measures according to the magnetic induction method. A magnetic field generated by a coil begins to interact with the magnetic portions of the specimen. The changes in the magnetic field induce a voltage proportional to the ferrite content in a second coil. This voltage is then evaluated. All magnetic portions in the otherwise non-magnetic structure are measured, i. e., in addition to delta ferrite and other ferritic portions also strain-induced martensite, for example.
A specific advantage of the magnetic induction method for measuring the ferrite content is that a sigma phase, i. e., a Fe-Cr precipitation, which has formed due to excess ferrite content and unfavourable cooling conditions, for example, is recognised correctly as a non-ferritic structural component. In comparison, erroneous interpretation of ferrite content is likely in a metallographic section where a sigma phase is not easily distinguished from a ferritic structure.
Fischer/菲希尔FeritScope fmp30铁素体含量测定仪
FeritScope FMP30根据磁感应方法测量奥氏体钢和双相钢中的铁素体含量
德国原装进口FeritScope FMP30铁素体含量检测仪
不锈钢焊缝铁素体检测仪器FERITSCOPE MP30
菲希尔铁素体检测仪探头FGAB1.3-Fe 604-264
铁素体测量仪品牌fmp30
不锈钢铁素体含量测定的一些问题
