SE420623B - AUSTENITIC, EXCEPTION CARDABLE STAINLESS CHROME-NICKEL ALUMINUM STEEL - Google Patents

Description

15 20 25 30 35 1919719-9 The steel was melted in a 10-ton high-frequency furnace, cast in molds and rolled into wire blanks. These have been blank treated and rolled to wire 0 6.0 mm of charge 3423-71 and 0 5.6 mm of charge # 029-71. Normal annealing at 105000, pickling and sewing have been carried out before the wire is pulled.

For comparison, a batch (3226-71) has been manufactured in the same way in steel of type 17-7 PHÅAISI 631), which is a precipitation hardening Cr-Ni-Al steel with the following analysis.

Table 2 ___ ë_Cha1 "e E §iM_H-_Pi § 02 111212 H fl Li 3226-71 .073 .74 .74 .013 .006 16.4 7.1 .l5 .0Ul .QR .09 Charge 3423-71 according to table l and charge 3226-71 The breaking limit (Rm), yield strength (Re) and contraction (Z) are compared in the attached Fig. 1. As can be seen, the yield strength and yield strength increase more slowly for the alloy according to the invention (solid line) which In addition, the ductility measured as contraction is always higher for the alloy according to the invention, especially at larger reductions. It is noteworthy that the material lacks stress cracks at as large an area reduction as 92%. brought with 17-7 PH where the risk of stress cracks is already at 45% reduction.

The precipitation hardening effect of the alloy according to the invention has been tested at two different reductions and has given the results according to Table 3 below.

Table 3 Rm N / mmz Re N / mmz Charge Dimension Reduction Tempered Tempered Tempered Tempered mm% 0 3423-71 2.68 80.0 1810 1995 1830 1855 4029-71 1.83 89.4 2116 2525 1976 2357 Temperature temperature 95000 for 30 minutes.

It seems that you get a tempering effect of approx. 200 N / mm2 for charge 3423-71 and approx. 400 N / mmz for charge 4029-71. The large difference between these effects is explained by the fact that charge 3H23-71 has not been reduced sufficiently before tempering, i.e. the austenite has not been sufficiently converted to martensite. 1a '15 20. 25 30 7910719-9 5 ° n The alloy according to the invention has mainly been developed to improve the cold workability of precipitation-curing stainless cr-Ni-Al-srál. within the surface Aßcn in Fig. 2, the analysis can be directed so that when annealing in the temperature range 600-950 ° C, an increase in the Ms temperature is obtained by carbide precipitation. Thereafter, the material can be quenched and possibly cooled to temperatures below room temperature to obtain a conversion to martensite which can then be annealed.

An interesting application is particularly cold spreading when such low breaking strengths as SUG-560 N / mmz have been measured on materials annealed at the temperature 105000. This applies to both charges 3423-71 and H029-71.

The technical effect of the invention is apparent from the fact that the drawability is significantly improved while maintaining a precipitation hardening effect. On good grounds, it can be assumed that good weldability can be improved with the addition of zirconium and uranium instead of titanium. As the alloy has a very slow martensite conversion in the annealed state, the material can be stored and transported outdoors in cold weather without the risk of spontaneous martensite formation. Chromium and nickel must be within the surface ABCD according to Fig. 2 where chromium can be partially replaced by molybdenum by up to a maximum of 2% according to the formula Cr '(chromium equivalent) =% Cr +% Mo, and nickel can be partially replaced by manganese according to formula Ni '(nickel equivalents) =% Ni + 1/2 (% Mn - 1%). In the particularly preferred embodiment, the chromium and nickel equivalents Cr 'and Ni' should be within the surface of the figure. The alloy according to the invention is annealed in the temperature range 600-950 ° C, quenched and cooled below room temperature.

The alloy can then be hardened by precipitation.

The alloy can also be quenched immediately after hot forging and cold worked and precipitation hardened thereafter.

Claims (2)

7916719-9 Patent claims Anstenitic, precipitation hardenable, stainless chromium-nickel-aluminum steel with good cold workability, characterized in that the chromium equivalent Cr 'defined according to the formula Cr' =% Cr +% Mo is between 16.5% and 18.2 % and the nickel equivalent Ni 'defined according to the formula Ni' =% Ni + 1/2. (% Mn- 1%) is between 8.25% and 9.75% within the surface abcd of the attached drawing figure 2, and the steel contains 10.5 - 18.2% Cr, 5.0 - 9.75% Ni , C up to 0.15%, Si up to 3.0%, Mn up to 8.0%, P up to 0.0 # 5%, S up to 0.040%, Mo up to 2.0%, N up to 0.15%, 0.5 - 2.5% Al and preferably one or more of the metals Ti, Zr and U up to 2%, the remainder being iron and stainless steel normally found in impurities. Steel according to claim 1, characterized in that it contains either Ti up to 0.5% or Zr up to 0.5% or U up to 1%.