High Temperature Properties Stainless Steel

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Stainless steel have good strength and good resistance to corrosion and OKSİDASYON at elevated temperatures. Stainless steel are used at temperatures up to 1700° F for 304 and 316 and up to 2000 F for the high temperature stainless grade 309(S) and up to 2100° F for 310(S). Stainless steel is used extensively in ısı eşanjörü, super-heaters, kazan, feed water heaters, valves and main steam lines as well as aircraft and aerospace applications.

Figure 1 gives a broad concept of the hot strength advantages of stainless steel in comparison to low carbon unalloyed steel. Table 1 shows the short term Çekme Dayanımı ve akma dayanımı vs temperature. Table 2 shows the generally accepted temperatures for both intermittent and continuous service.

With time and temperature, changes in metallurgical structure can be expected with any metal. In stainless steel, the changes can be softening, carbide Yağış, or embrittlement. Softening or loss of strength occurs in the 300 series (304, 316, etc.) stainless steel at about 1000° F and at about 900° F for the hardenable 400 (410<, 420, 440) series and 800° F for the non-hardenable 400 (409, 430) series (refer to Table 1).

Karbür çökelmesi can occur in the 300 series in the temperature range 800 – 1600° F. It can be deterred by choosing a grade designed to prevent carbide precipitation i.e., 347 (Cb added) or 321 (Titanyum added). If carbide precipitation does occur, it can be removed by heating above 1900° and cooling quickly.

Hardenable 400 series with greater than 12% chromium as well as the non-hardenable 400 series and the dubleks paslanmaz çeli̇k are subject to embrittlement when exposed to temperature of 700 – 950° F over an extended period of time. This is sometimes call 885F embrittlement because this is the temperature at which the embrittlement is the most rapid. 885F embrittlement results in low ductility and increased sertlik ve Çekme Dayanımı at room temperature, but retains its desirable mekani̇k özelli̇kler at operating temperatures.

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Table 1 Short Term Çekme Dayanımı vs Sıcaklık (410 hariç tavlanmış durumda)

Sıcaklık	304 & TS ksi	316 YS ksi	309 & TS ksi	309S YS ksi	310 & TS ksi	310S YS ksi	410* TS ksi	YS ksi	430 TS ksi	YS ksi
Oda Sıcaklığı.	84	42	90	45	90	45	110	85	75	50
400°F	82	36	80	38	84	34	108	85	65	38
600°F	77	32	75	36	82	31	102	82	62	36
800°F	74	28	71	34	78	28	92	80	55	35
1000°F	70	26	64	30	70	26	74	70	38	28
1200°F	58	23	53	27	59	25	44	40	22	16
1400°F	34	20	35	20	41	24	—	—	10	8
1600°F	24	18	25	20	26	22	—	—	5	4

* ısıl işlem görmüş by oil quenching from 1800° F and tempering at 1200° F

Table 2 Generally Accepted Service Sıcaklıklar

Malzeme	Aralıklı Servis Sıcaklığı	Sürekli Servis Sıcaklığı
Östenitik
304	1600°F (870°C)	1700°F (925°C)
316	1600°F (870°C)	1700°F (925°C)
309	1800°F (980°C)	2000°F (1095°C)
310	1900°F (1035°C)	2100°F (1150°C)
Martensitik
410	1500°F (815°C)	1300°F (705°C)
420	1350°F (735°C)	1150°F (620°C)
Ferritik
430	1600°F (870°C)	1500°F (815°C)

It may seem to be illogical that the “continuous” service temperature would be higher than the “intermittent” service temperature for the 300 series grades. The answer is that intermittent service involves “thermal cycling”, which can cause the high temperature scale formed to crack and spall. This occurs because of the difference in the coefficient of expansion between the stainless steel and the scale. As a result of this scaling and cracking, there is a greater deterioration of the yüzey than will occur if the temperature is continuous. Therefore the suggested intermittent service temperatures are lower. This is not the case for the 400 series (both ferritic and martensitic grades). The reason for this is not known.

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Table 1 Short Term Çekme Dayanımı vs Sıcaklık (410 hariç tavlanmış durumda)

Table 2 Generally Accepted Service Sıcaklıklar

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