Introduction to stainless steels ■ Stainless steels The great variety of stainless steels makes them the most important materials in the industrial world. As early as the beginning of the 20th century it was observed that certain steel alloys did not show any signs of corro- sion, or corrode only very slowly. Back then, different steel mills did research with steel types that were as- sumed to be corrosion-resistant. For example, research done by the German Krupp company and the Austrian Max Mauermann led to the development of an austen itic variant with a chromium content of 18% and a nickel content of approx. 10%. Today, this alloy is known as A 2 (formerly know as V2A) or, with added molybdenum, as A4 (formerly V4A). sufficient chromium locally under certain conditions. Stainless steels with large carbon content show this be- haviour. Carbon will then react with the chromium to form chromium carbides and thus leave no way for the material to form a sufficiently thick passive layer. Where there is not enough unbonded chromium the steel sur- face becomes susceptible to salts and chlorides. This may be avoided by using grades with low carbon con- tent such as ma terial 1.4404 or titanium alloy such as material 1.4571. Also, increasing the chromium content improves the formation and resistance of the passive layer. This is beneficial in the so-called duplex steels with chromium content partly up to 26%. But what exactly does the term “stainless steel” mean? It applies to steels, which under “normal” climactic con- ditions do not corrode. Corrosion in this context is red rust, i.e. the product of the reaction between iron and oxygen. Stainless steels have a corrosion self-protection property generated by a natural resistance coating. The chromium in the steel alloy reacts on the exposed surface with the atmospheric oxygen to form chromium oxide, and this creates a very thin, but hard and airtight, passive layer which protects the steel from corrosion. If this passive layer is damaged, i.e. while the steels are being processed or in use, the surface protection will regenerate itself within a few hours, depending on the environmental conditions. In order to form the chro- mium oxide layer, the chromium content must be suffi- ciently high along the entire surface, and the surround- ing air must contain oxygen. Foil-protected stainless steel sheets, for example, do not have such a passive layer yet, as there is no oxygen available under the foil. But, also, the material itself may sometimes not provide 2 In addition to the purely ferritic, austenitic and martens- itic grades, duplex grades, which have a mixed structure of austenite and ferrite, were also produced in the 1930s. However, duplex steels back then were not stable enough to be used for technical purposes. This has changed very recently by adding nitrogen. Today we compare four material groups of stainless steels: austenites (A), fer rites (F), martensites (C) and duplex steels (D). Page ■ Contents Introduction to stainless steels Material groups 2 3 4–8 Materials 9 10 11–14 Properties of stainless steels Corrosion resistance Technical expertise

Materials ■ Overview of materials – extract from ISO 3506-6 Steel type Material code Properties 1.4305 (X8CrNiS18-9) 1.4301 (X5CrNi18-1O) 1.4541 (X6CrNiTi18-1O) 1.4550 (X6CrNiNb18-1O) 1.4590 (X2CrNbZr17) 1.4401 (X5CrNiMo17-12-2) 1.4435 (X2CrNiMo18-14-3) 1.4436 (X3CrNiMo17-13-3) 1.4439 (X2CrNiMoN17-13-5) 1.4571 (X6CrNiMoTi17-12-2) 1.4580 (X6CrNiMoNb17-12-2) 1.4006 (X12Cr13) 1.4021 (X20Cr13) 1.4057 (X17CrNi16-2) 1.4005 (X12CrS13) 1.4104 (X14CrMoS17) 1.4016 (X6Cr17) 1.4529 (X1NiCrMoCuN25-20-7) ■ for machining production ■ partially corrosion-resistant ■ partially acid-resistant ■ partially weldable ■ for cold/hot forging ■ corrosion-resistant ■ partially acid-resistant ■ good weldability ■ for cold/hot forging ■ highest corrosion resistance ■ partially acid-resistant ■ good weldability ■ partially corrosion-resistant ■ partially corrosion-resistant ■ for machining ■ corrosion-resistant ■ partially acid-resistant ■ very suitable for environments with high chloride content ■ good mechanical properties ■ extremely high resistance to pitting corrosion, stress corrosion and crevice corrosion 1.4482 (X2CrMnNiMoN21-5-3) ■ outstanding mechanical properties ■ low nickel content 1.4362 (X2CrNiN23-4) ■ outstanding mechanical properties ■ good resistance to stress corrosion and intergranular corrosion 1.4462 (X2CrNiMoN22-5-3) 1.4481 (X2CrNiMoN25-7-3) ■ outstanding mechanical properties ■ high resistance to stress corrosion in media containing chloride, and to pitting corrosion 1.4410 (X2CrNiMoN25-7-4) 1.4501 (X2CrNiMoCuWN25-7-4) 1.4507 (X2CrNiMoCuN25-6-3) ■ outstanding mechanical properties ■ excellent corrosion resistance in case of corrosive chemicals such as sulphuric acid, phosphoric acid and nitric acid A 1 A 2 A 3 A 4 A 5 C 1 C 3 C 4 F 1 A 8 D 2 D 4 D 6 D 8 4

Materials DUPLEX ST ■ Components of duplex steels ■ Properties of duplex steels The name “duplex” describes a material which is com- posed of equal amounts of ferrites and austenites. The combination of these two components brings out their particular advantages. For example, the 0.2% yield strength with equal ductility is higher in duplex than in austenitic materials. Moreover, the fatigue strength un- der corrosive conditions is also higher for duplex steels. The mixed austenite and ferrite structure is set by redu- cing the nickel content. Correspondingly, the chromium content must be increased. The common material 1.4462 contains 22% chromium, but only 5% nickel. Due to the increased chromium content, duplex steels are more resistant to corrosion than austenitic materials under various conditions of use. Nitrogen is another very im- portant alloying element for this steel type. It helps form austenite, so that a homogeneous distribution of ferrite and austenite is assured. Also, the resistance of the austenitic phase to stress crack corrosion is improved largely by adding nitrogen. The ferritic phase shows superior resistance due to the combined chromium and molybdenum content. Although the principle of duplex steels has been known for decades, this steel type was not accepted for a long time because of difficulties during welding. In this respect, the modern alloys have been developed and improved, so that now duplex steels have become easier to use and therefore more commercially important in recent years. In the field of fasteners, these materials are becoming more commonly used, which is proven by in- corporating these materials into ISO 3506-1 and -2. In this standard, material groups D 2, D 4, D 6 and D 8 have now been defined specifically for fasteners. Just like for all other material groups, only a rough analysis is defined. However, if this is compared to the common materials, it shows that Lean-Duplex 1.4362 for group D 4 and standard duplex materials 1.4462 and 1.4410 for group D 6 will probably dominate. This is because they have a higher basic strength com- pared to austenites, therefore it is easier to achieve higher final strength values with duplex steels. The property class 100 is thus a very interesting supplement and with its tensile strength of 1,000 MPa and a yield strength of 800 MPa it achieves strength values, which are only slightly below those of a carbon steel screw of property class 10.9. ■ Fields of application for duplex steels Due to the above-mentioned properties duplex steels may be used in all fields of application in which the corrosion resistance or yield strength of austenitic steels is not sufficient. As they are more resistant to chlor ide- induced stress corrosion compared to the austenitic materials, it is also possible to improve the resistance against saltwater or thawing salt. 6

Materials ■ Standard materials and special materials in the REYHER product range Standard materials Special materials We offer you a wide range of stainless steel products made of standard materials that we keep in stock. Therefore, we are able to supply you with all the articles you desire. Please find below our product groups and standard materials: In addition to standard materials from the range of stainless steels we also offer a variety of special materials. Here is an extract: ▶ Precipitation hardenable grades, material 1.4568 (17-7 PH), material 1.4548 (17-4 PH) ▶ 6-Mo-grades, e.g. materials 1.4547 (254 SMO) or ▶ Austenitic steels made of A 2 with nominal diameters from M 2 to M 48 1.4529 ▶ Heat-resistant and high-temperature-resistant grades, e. g. materials 1.4980, 1.4913 and 1.4923 We offer products for all fields of application. We gladly offer advice and support regarding your indi- vidual material requirements. We do the sourcing for you and can also add all the articles you need to our stock. ▶ Austenitic steels made of A 4 with nominal diameters from M 2 to M 48 ▶ Austenitic steels made of A 5 with nominal diameters from M 6 to M 30 ▶ Duplex steels made of D 6 with nominal diameters from M 6 to M 16 ▶ BUMAX® – high-strength stainless steel fasteners of the product group BUMAX 88 (corresponds to the steel property class 8.8) ▶ BUMAX® – high-strength stainless steel fasteners of the product group BUMAX 109 (corresponds to the steel property class 10.9) 8

Technical expertise ■ Technical expertise with REM – REYHER Engineering Management gladly give advice. We are happy to hear from you and to support you in case of technical questions. Technical hotline: Phone +49 40 85363-999 Our REM team takes care of all technical matters and details regarding fasteners and fixing technology. With continuous training our comprehensive expertise is kept up to date. This is your advantage as our client. For fasteners made of stainless steel we gladly support you in selecting the right materials for your particular application. In order to choose the right material, a multi- plicity of application parameters has to be considered, such as temperature or exposure to corrosive substances, for example. Our expert engineers and technicians will 10

Properties of stainless steels Quality testing in our internal testing laboratory: determining friction coefficients ■ High friction coefficients in bolted joints and in galling Besides other property classes, fasteners made of stain- less steels also show different friction behaviour than screws made of carbon steel, which must be considered for assembly. it be avoided, but is also possible to calculate the preload and the corresponding tightening torque. Copper paste is a suitable lubricant, but also ceramic lubricants or dry film lubricants, which are applied in advance. If two stainless steel elements are fastened, the friction coefficients in the thread and on the contact surfaces are higher than with quenched and tempered screws. In addition, the spread is also much higher. Targeted preloading without lubricating the fasteners is nearly impossible. Friction may be so high that it leads to galling, depend- ing on the assembly conditions. It is assumed that during assembly the temperatures get so high locally that this leads to “weld” in a microscopic range. By tightening the fastener more, the “weld” is torn. This leads to in- creased surface roughness, which makes it even harder to turn the screw or nut. This step is repeated until the fastener can not be turned any further. By using lubricants, the friction coefficients can be mod- ified in a targeted manner. This way, not only can galling 12 Our product range in the field of stainless steels also comprises lubricated products. For example, all products made of duplex steel are generally lubricated. We also offer lubricated Bumax products, where only the class 88 bolts are lubricated by default. In the case of our bolts per ISO 4032 made of A 2-70 and A 4-70 you may choose with or without lubrication, as we offer both. For applications for which a defined preload must be set, we recommend determining the tightening torques by testing in environments which reflect the actual condi- tions. This is possible with a torque-preload test. We gladly support you with this.

Properties of stainless steels ■ Property classes As austenitic materials cannot be hardened with heat treatment, they have the property class 50 in unpro- cessed delivery condition, which corresponds to a tensile strength of 500 MPa. In non-machining production, they are strain hardened; in this process, the tensile strength values of austenitic materials may rise up to 1,000 MPa (property classes 70 + 80 + 100). As the harden ing pressure such as in the case of thread rolling is limited, the property class 70, which is common in practice, may be achieved in screws with a maximum size of up to M 24. In solution heat treated condition, duplex steels reach higher strength values already, and may thus also be hardened to a higher property class by strain hardening. For these grades, the property classes 70, 80 and 100 are standardised. We have property class 100 in stock, which corresponds to a tensile strength of 1,000 MPa and a yield strength of 800 MPa. Unlike with steel screws, there is no linear connection between the tensile strength and the 0.2% yield strength. The yield strength corresponding to the tensile strength 50, 70, 80, and 100 is listed in the table below. The mechanical and chemical properties for corro- sion-resistant fasteners are defined in DIN EN ISO 3506- 1, -2 and -3. Steel group Steel type Property class Tensile strength 0.2% yield strength Elongation after fracture A 1, A 2, A 3 Austenitic A 4, A 5 A 8 C 1 C 3 C 4 Martensitic Duplex D 2, D 4, D 6, D 8 14 50 70 80 50 70 80 100 70 80 100 50 70 110 80 50 70 70 80 500 700 800 500 700 800 1,000 700 800 1,000 500 700 1,100 800 500 700 700 800 100 1,000 210 450 600 210 450 600 800 450 600 800 250 410 820 640 250 410 450 600 800 0.6d 0.4d 0.3d 0.6d 0.4d 0.3d 0.2d 0.4d 0.3d 0.2d 0.2d 0.2d 0.2d 0.2d 0.2d 0.2d 0.4d 0.3d 0.2d

+49 40 85363-0 mail@reyher.de www.reyher.de F. REYHER Nchfg. GmbH & Co. KG Haferweg 1 22769 Hamburg Germany ■ REYHER informs: Stainless steels ✔ Overview of material groups austenites (A), ferrites (F), martensites (C) and duplex steels (D) ✔ REYHER offers fasteners made of stainless steels for all fields of application ✔ New in the REYHER product range: duplex steels ✔ Technical consulting ✔ Stock products available immediately Note: REYHER is not the manufacturer of these products. The manufacturer reserves the right to make technical changes. Understandably, the application of the products listed requires expertise on their use and assembly as well as standards. 0 0 0 . 1 2 0 2 . 1 2 2 . 6 0 4 9 4 2 2 1 0 / 1 / 1 N E / 1 1 P