Heat-resistant, austenitic cast steel having excellent machinability and exhaust member made thereof

Patent metadata

Field	Value
Publication number	US-9765678-B2
Application number	US-201314399648-A
Country	US
Kind code	B2
Filing date	May 9, 2013
Priority date	May 10, 2012
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A heat-resistant, austenitic cast steel having excellent machinability comprising by mass 0.4-0.55% of C, 1-2% of Si, 0.5-1.5% of Mn, 18-27% of Cr, 8-22% of Ni, 1.5-2.5% of Nb, 0.01-0.3% of N, 0.1-0.2% of S, and 0.02-0.15% of Al, the balance being Fe and inevitable impurities, a machinability index I represented by the following formula: I=100×S+75×Al+0.75×Mn−10×C−2×Nb−0.25×Cr−0.15×Ni−1.2×N, wherein each element symbol represents % by mass of each element in the cast steel, meeting the condition of −3.0≦I≦+14.0, and an exhaust member made thereof.

First claim

What is claimed is:

1. A heat-resistant, austenitic cast steel, which consists of by mass
0.4-0.55% of C,
1-2% of Si,
0.5-1.5% of Mn,
18-27% of Cr,
8-22% of Ni,
1.5-2.5% of Nb,
0.01-0.3% of N,
0.1-0.2% of S, and
0.02-0.15% of Al,
the balance being Fe and inevitable impurities;
a machinability index I expressed by the following formula:
I=100×S+75×Al+0.75×Mn−10×C−2×Nb−0.25×Cr−0.15×Ni−1.2×N,

wherein each element symbol represents % by mass of each element in the cast steel, meeting the condition of −3.0≦I≦+14.0.

2. The heat-resistant, austenitic cast steel according to claim 1 , which has a structure, in which the area ratio of sulfide particles having equivalent circle diameters of 2 μm or more to all sulfide particles is 60% or more.

3. The heat-resistant, austenitic cast steel according to claim 1 , wherein when it is milled with a cemented carbide tool at a cutting speed of 150 m/minute, a feed of 0.2 mm/tooth, and a cutting depth of 1.0 mm, under a dry condition without a cutting liquid, a tool life expressed by cutting time until the flank wear of the cemented carbide tool reaches 0.2 mm is 25 minutes or more.

4. An exhaust member made of the heat-resistant, austenitic cast steel recited in claim 1 .

Assignees

• Hitachi Metals Ltd

Inventors

• Morishita Kana
• Inoue Kenichi
• Katsuragi Susumu
• Kawabata Masahide
• SAKUTA Tomonori

Classifications

• C22C38/60

  containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title

• C22C38/34

  with more than 1.5% by weight of silicon · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/04

  containing manganese · CPC title