山特维克 SAF 2304®

Sandvik SAF 2304® 具有良好的机械和物理性能、出色的抗应力腐蚀开裂和其他形式的腐蚀以及良好的可焊性。这些特性使其在技术和经济上均优于不锈钢，例如奥氏体钢 ASTM 304、304L、316、316L、321 和 347，铁素体铬钢 ASTM 430 和 444 以及马氏体铬钢 ASTM 410 和420型。与低合金钢相比，山特维克 SAF 2304® 还具有优势。下表列出了山特维克 SAF 2304® 优于其他材料的示例。

良好的机械性能和耐腐蚀性能使 Sandvik SAF 2304® 通过降低设备的生命周期成本成为许多应用中的经济选择。

3RE60 的高强度和硬度使该材料在承受重载或磨损的结构中成为奥氏体钢的有吸引力的替代品。

批准：

如果 Sandvik SAF 2304® 长时间暴露在超过 280°C (540°F) 的温度下，微观结构会发生变化，从而导致冲击强度降低。这不一定会影响材料在工作温度下的行为。例如，热交换器管可以在更高的温度下使用而没有任何问题。请联系山特维克了解更多信息。对于压力容器应用，根据 VdTÜV-Wb 496，要求最高温度为 280°C (540°F)。

Sandvik SAF 2304® 弯曲所需的起始力略高于 ASTM 304/316。 Sandvik SAF 2304® 可冷弯至 25% 变形，无需后续热处理。在应力腐蚀开裂风险开始增加的使用条件下，例如材料温度接近 125°C (255°F)，在大约 100 ppm Cl⁻ 的中性含氧环境中，建议即使在中度冷弯。对于德国和北欧国家的压力容器应用，在冷变形后可能需要根据 VdTÜV-Wb 496 和 NGS 1607 进行热处理。热处理以固溶退火（参见热处理）或电阻退火的形式进行。

一般腐蚀：由于铬含量高且成分均衡，Sandvik SAF 2304® 在酸性环境中具有出色的耐腐蚀性。下表给出了不同酸中的腐蚀速率，图 4-6 分别显示了 Sandvik SAF 2304® 在硫酸、甲酸和硝酸中的等腐蚀图。

Corrosion rates in acid-water mixtures, mm/year (mpy). Activated specimens, 1+3+3 days, average of the last two periods for two specimens.

Pitting:The pitting resistance of a steel is determined primarily by its chromium and molybdenum contents, but the nitrogen content also has an effect.制造和制造实践，例如welding, are also of vital importance for the actual performance in service.

A parameter for comparing the pitting resistance of different steels is the PRE-number (Pitting Resistance Equivalent).

PRE定义为，以重量-%为单位

PRE =% Cr + 3.3 %x Mo + 16 x % N

As the table shows, the PRE number for Sandvik SAF 2304® is considerably higher than the number for ASTM 304L and comparable to the number for ASTM 316L. Potentiostatic tests in solutions with different chloride contents (pH =6) are reported in Figure 7. Each curve is based on at least 4 measuring points, each of which is derived from a minimum of three separate measurements. Variation in the measurement results is within the range +/-5°C (+/-9°F). The test results for ASTM 316L have been compared with results obtained under practical conditions of service, and the correlation is good. As is evident from Figure 7, the critical temperature for pitting for Sandvik SAF 2304® is higher than that for ASTM 304L and comparable to that for ASTM 316L. The test results correspond with the PRE ranking.

Stress corrosion cracking:Because of its two-phase structure and its well balanced composition, Sandvik SAF 2304® possesses very good resistance to stress corrosion cracking (SCC). This is evident from the results of tests in both concentrated chloride solutions and oxygen-containing dilute chloride environments.

Figure 8 shows the results of tests carried out in 40% CaCl₂ solution at 100°C (210°F). In this environment, the stress that is required to cause fracture due to SCC (known as the threshold stress) is much higher for Sandvik SAF 2304® than for ASTM 304/304L and ASTM 316/316L. This demonstrates the superior resistance of Sandvik SAF 2304®.

Welding of Sandvik SAF 2304® does not appreciably reduce the resistance to SCC, provided that the welding recommendations are followed (see Welding). The threshold stress of material that has been TIG-welded with Sandvik 22.8.3.L or MMA-welded with Sandvik 22.9.3.LR is on a level with that of the parent metal.

The results of SCC testing of Sandvik SAF 2304 in chloride solutions at high temperatures and pressures are presented in Figure 9. The curve for Sandvik SAF 2304® is based on tests performed in various chloride contents and at different temperatures. Usually, six separate measurements were taken at each measuring point. The testing method involved spring-loaded specimens stressed to the proof strength (Rp0.2) at the testing temperature or U-bends in which the stress at the apex is at least equal to the proof strength of the solution annealed material. The oxygen content of the inlet water (refreshed autoclaves were used) was 4.6 to 10 ppm and the pH 4.5 to 7. The curve for ASTM 304/304L and ASTM 316/316L is based on published test results and on practical experience.

The results in Figure 9 indicate that Sandvik SAF 2304® can be used in dilute oxygen-bearing chloride solutions up to about 125°C (260°F) without any risk of SCC. This is much higher than for ASTM 304/ 304L and ASTM 316/316L, which should not be used above 60°C (140°F) in such environments. At temperatures above 125°C (260°F), Sandvik SAF 2304® should not be used in oxygen-bearing solutions in environments with more than about 10 ppm Cl-. For such conditions, we recommend Sandvik SAF 2205™, Sandvik SAF 2507® or Sanicro® 28. At low oxygen contents, which are common in the process and power industries, considerably higher chloride contents and temperatures can be tolerated by Sandvik SAF 2304® without any risk of SCC.

Intergranular corrosion:Sandvik SAF 2304® is a member of the family of modern duplex stainless steels whose chemical manner that the reformation of austenite in the heat-affected zone adjacent to the weld takes place quickly. This results in a microstructure that gives corrosion properties and toughness similar to that of the parent metal. Welded joints in Sandvik SAF 2304® easily pass Strauss' intergranular corrosion testing according to SS-EN ISO 3651-2 Method A.

Crevice corrosion:In the same way as the resistance to pitting can be related to the chromium, molybdenum and nitrogen contents of the steel so can the resistance to crevice corrosion. Sandvik SAF 2304® possesses better resistance to crevice corrosion than steels of the ASTM 304/304L type and is comparable with ASTM 316/316L.

Erosion corrosion:Steels of the ASTM 304/304L and ASTM 316/316L type can be attacked by erosion corrosion if exposed to flowing media containing highly abrasive solid particles, e.g. sand, or media with very high flow rates. Under such conditions, Sandvik SAF 2304® displays very good resistance because of its combination of high mechanical strength and good corrosion resistance.

Corrosion fatigue:Sandvik SAF 2304® possesses higher strength and better corrosion resistance than ordinary austenitic stainless steels. Consequently, Sandvik SAF 2304® has considerably better fatigue strength under corrosive conditions than such steels.

Expanding

In comparison with austenitic stainless steels, Sandvik SAF 2304® has a higher proof strength. This must be borne in mind when expanding tubes into tube-sheets. Normal expanding methods can be used, but the expansion requires higher initial force and should be undertaken in one operation.

Contact us for detailed recommendations on expanding duplex stainless steels.

管子通常在热处理状态下交付。如果由于进一步加工需要额外的热处理，建议使用以下方法。

Solution annealing:930 -1050°C (1710 -1920°F), rapid cooling in air or water.

Hot bending is carried out at 1100-950°C (2010-1740°F) and should be followed by solution annealing.

Being a two-phase material (austenitic-ferritic) Sandvik SAF 2304® will present a different tool wear profile from that of single-phase steels of type ASTM 304L. The cutting speed must, therefore, be slightly lower than that recommended for ASTM 304L and as a first recommendation 25 % lower cutting speeds should be used compared to the speed for machining Sanmac 304/304L. It is, however, recommended that a tougher insert grade is used for semi-roughing operations, Sanmac® 304/304L.

供货形式：

Seamless tube and pipe in Sandvik SAF 2304® is supplied in dimensions up to 260mm outside diameter. The delivery condition is solution annealed and either white pickled or bright annealed.

For hydraulic tubing applications, Sandvik SAF 2304® is also marketed under the name PW 400.

Other forms of supply

The weldability of Sandvik SAF 2304® is good.焊接必须在没有预热的情况下进行，通常不需要随后的热处理。合适的熔焊方法是手工电弧焊（MMA/SMAW）和气体保护电弧焊，首选TIG/GTAW方法。

For Sandvik SAF 2304®, heat input of 0.5-2.5 kJ/mm and interpass temperature of <150°C (300°F) are recommended.

Recommended filler metals

• TIG/GTAW 或 MIG/GMAW 焊接
  • ISO 14343 S 23 7 N L (e.g. Exaton 23.7.L)
  • ISO 14343 S 22 9 3 N L / AWS A5.9 ER2209 (e.g. Exaton 22.8.3.L)
• MMA/SMAW 焊接
  • ISO 3581 E 23 7 N L R
  • ISO 3581 E 22 9 3 N L R / AWS A5.4 E2209-17 (e.g. Exaton 22.9.3.LR)