Steel material for vacuum tube and method of manufacturing same

Patent metadata

Field	Value
Publication number	US-2023024943-A1
Application number	US-202017786054-A
Country	US
Kind code	A1
Filing date	Dec 9, 2020
Priority date	Dec 18, 2019
Publication date	Jan 26, 2023
Grant date	—

Abstract

A steel material for a vacuum tube according to an aspect of the present disclosure may include C: 0.1˜0.2%, Si: 0.05∞0.5%, Mn: 1.0∞1.6%, Ni: 0.5∞1.0%, Cr: 1.5∞4.0%, and the balance of Fe and unavoidable impurities in percentage by weight, and may have a complex structure of ferrite and pearlite as a microstructure.

First claim

1 . A steel material for a vacuum tube, the steel material comprising
C: 0.1˜0.2%, Si: 0.05˜0.5%, Mn: 1.0˜1.6%, Ni: 0.5˜1.0%, Cr: 1.5˜4.0%, and the balance of Fe and unavoidable impurities in percentage by weight, wherein the steel material has a complex structure of ferrite and pearlite as a microstructure, and an outgassing rate of the steel material is 1.0*10 −10 mbar·l·s −1 ·cm −2 or less.

2 . The steel material of claim 1 , wherein a total content of Ti, Nb, and V of the impurities included in the steel material is less than 0.01% (including 0%).

3 . The steel material of claim 1 , wherein a fraction of the ferrite is 60˜90 percent by area, and
a fraction of the pearlite is 10˜40 percent by area.

4 . The steel material of claim 1 , wherein a fraction of martensite or bainite included in the steel material is less than 1 percent by area (including 0%).

5 . The steel material of claim 1 , wherein the steel material has yield strength (YS) of 400˜600 MPa, a yield ratio (YR) of 0.8 or less, and elongation (El) of 19˜30%.

6 . The steel material of claim 1 , wherein the steel material has Charpy impact energy of 30˜50 J at −20° C.

7 . The steel material of claim 1 , wherein a thickness of the steel material is 5˜30 mm.

8 . A method of manufacturing a steel material for a vacuum tube, the method comprising:
providing a steel material by reheating a slab including C: 0.1˜0.2%, Si: 0.05˜0.5%, Mn: 1.0˜1.6%, Ni: 0.5˜1.0%, Cr: 1.5˜4.0%, and the balance of Fe and unavoidable impurities in percentage by weight, and then by hot-rolling the slab at a finishing rolling temperature of 900˜1000° C.; primarily cooling the hot-rolled steel material up to a temperature range of 550˜650° C. at a primary cooling speed of 5˜50° C./s; coiling the steel material into a coil at a primary cooling end temperature after the primary cooling; and secondary cooling the coil to room temperature at a secondary cooling speed of 0.005˜0.05° C./s.

9 . The method of claim 8 , wherein a total content of Ti, Nb, and V of the impurities included in the slab is less than 0.01% (including 0%).

10 . The method of claim 8 , wherein a thickness of the hot-rolled steel material is 5˜30 mm.

11 . The method of claim 8 , wherein a cooling type of the primary cooling is water cooling, and
a cooling type of the secondary cooling is discharge of cold.

Assignees

• Posco

Inventors

• Yang Hong-Seok
• Choi Jae-Hun
• Kim Hak-Jun
• Seo Seok-Jong

Classifications

• C22C38/02

  containing silicon · CPC title

• C21D2211/009

  Pearlite · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C21D8/0226

  Hot rolling · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title