V145- Precipitation Hardening

Valbruna Grade

V145

Description of material

V145 is a martensitic precipitation hardening stainless steel with good mechanical properties and better corrosion resistance when compared to the typical series of martensitic grades. Metallurgical behavior during aging is basically the same of V174 grade, while its hardness in solution annealing is a little lower.

Applications

It can be used in a number of different kinds of applications, such as valves, chemical and power productions components, engine parts, fitting, fasteners, shafts and pumps shafts and parts for oil & gas plants.

Melting practices

Argon Oxygen Decarburization

Corrosion resistance

This grade has the same general corrosion resistance as austenitic SS 304, but better than the group of standard martensitic 400 series steels. For some applications, it could be used in the solution treated condition, but for maximum resistance to chloride stress corrosion cracking, it should be aged at a high temperature such as 600-620°C. In Sulfide aggressive environments, also age at 620° C. The same choice should be done in the case of situations or environments prone to cause H-embrittlement. It should also be noted that for this grade, as for every kind of stainless steel, surfaces should be free of contaminants and scale, and passivated for optimum corrosion resistance.

Cold working

Cold deforming capacity of this grade in the annealed condition is better of V174 and V155. Nevertheless, severe cold working requires aging at the highest temperature particularly if cold processes were characterized by operations that could prime localized high strengths. To restore or increase mechanical properties such as tensile Rm and toughness, a new solution treatment followed by a suitable aging temperature should be carried out. Nevertheless, the repetition of a single aging could be sufficient evaluating if consistent with the final use.

Machinability

Machinability is good in both the solution-treated and precipitation hardening conditions considering that this property improves when hardness decreases. A certain amount of dimensional changes, in terms of contraction, happens after the aging of parts; these dimensional variations should be evaluated.

Weldability

This grade has a good weldability, doesn’t normally need preheating, and has an acceptable weld properties in as-welded conditions but welding design should be well evaluated in order to avoid situations prone to generate stress. Small sections could be weld in solution treatment condition followed by an aging; large or heavy sections require a suitable temperature aging obviously followed by a new solution treatment and an aging.

Hot working

Ingots or large forgings require a suitable preheating in order to avoid thermal cracking. Avoid overheating and improper cooling. Cool forging in air, and then solution treat. Large forging bars and shapes should be equalized at 1030 -1040°C in the heating furnace prior to cooling. Both small or large forgings, rolled rings, flanges or bars must be cooled until to complete the transformation of Martensite, obtaining a both good structure and mechanical properties after aging.

Designations