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US 2019/0100822 A1Published application
Method for joining steel rails with controlled weld heat input
AssigneeCF&I Steel, L.P.
InventorsGregory Ryan Lehnhoff, Joseph Victor Kristan, Mark David Richards
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Abstract
A method for creating a welded joint between ends of two steel rails, wherein the two steel rails have a substantially pearlitic microstructure. The method includes a first heating step, an upsetting step, a first cooling step, and a second heating step and provides a means to influence a microstructure and hardness of an austenitic region of a heat affected zone (HAZ) and/or an extent of softening in a softened region of a HAZ.
Claims41
A method for creating a welded joint between ends of two steel rails, wherein the two steel rails have a substantially pearlitic microstructure, the method comprising:
- a first heating step wherein the ends of the two steel rails are heated to obtain within the two steel rails:
- an austenitic region comprising a microstructure substantially of austenite, the austenitic region being within and/or adjacent to the ends of the two steel rails,
- a softened region adjacent to the austenitic region, the softened region comprising a microstructure substantially of softened, annealed, spheroidized, and/or degenerate pearlite, and
- an unaffected region adjacent to the softened region, the unaffected region comprising a microstructure that has not been substantially altered as compared to a starting microstructure of the two rails;
- an upsetting or forging step wherein the ends of the two steel rails are forced together to obtain:
- a weld bond between the ends of the two steel rails,
- a remaining austenitic region on both sides of the weld bond,
- a remaining softened region on both sides of the weld bond, and
- a remaining unaffected region on both sides of the weld bond;
- a first cooling step wherein a temperature of the austenitic region of at least one of the two steel rails is below an A1 temperature;
- and
- a second heating step wherein
- heat is applied to the austenitic region of at least one of the two steel rails to maintain the temperature of at least said austenitic region in a temperature range below said A1 temperature, and
- no additional austenite is formed, and
- a hardness of said austenitic region after the second heating step is less than or equal to a hardness in said austenitic region without the second heating step.
12 more elements
A method for creating a welded joint between ends of two steel rails, wherein the two steel rails have a substantially pearlitic microstructure, the method comprising:
- a first heating step wherein the ends of the two steel rails are heated to obtain within the two steel rails:
- an austenitic region comprising a microstructure substantially of austenite, the austenitic region being within and/or adjacent to the ends of the two steel rails,
- a softened region adjacent to the austenitic region, the softened region comprising a microstructure substantially of softened, annealed, spheroidized, and/or degenerate pearlite, and
- an unaffected region adjacent to the softened region, the unaffected region comprising a microstructure that has not been substantially altered as compared to a starting microstructure of the two rails;
- an upsetting or forging step wherein the ends of the two steel rails are forced together to obtain:
- a weld bond between the ends of the two steel rails,
- a remaining austenitic region on both sides of the weld bond,
- a remaining softened region on both sides of the weld bond, and
- a remaining unaffected region on both sides of the weld bond;
- a first cooling step wherein a temperature of the austenitic region of at least one of the two steel rails is below an A1 temperature;
- and
- a second heating step wherein
- heat is applied to the austenitic region of at least one of the two steel rails to maintain the temperature of at least said austenitic region in a transformation temperature range below said A1 temperature for a transformation hold time, and
- at least some of the austenite in at least said austenitic region transforms to another microstructure during the second heating step.
11 more elements
A method for creating a welded joint between ends of two steel rails, wherein the two steel rails have a substantially pearlitic microstructure, the method comprising:
- a first heating step wherein ends of the two steel rails are heated to obtain within the two steel rails:
- an austenitic region comprising a microstructure substantially of austenite, the austenitic region being within and/or adjacent to the ends of the two steel rails,
- a softened region adjacent to the austenitic region, the softened region comprising a microstructure substantially of softened, annealed, spheroidized, and/or degenerate pearlite, and
- an unaffected region adjacent to the softened region, the unaffected region comprising a microstructure that has not been substantially altered as compared to a starting microstructure of the two steel rails;
- an upsetting or forging step wherein the ends of the two rails are forced together to obtain:
- a weld bond between the two steel rail ends,
- a remaining austenitic region on both sides of the weld bond,
- a remaining softened region on both sides of the weld bond, and
- a remaining unaffected region on both sides of the weld bond;
- a first cooling step wherein a temperature in the austenitic region of at least one of the two steel rails is below an Ms temperature, such that at least some martensite is formed from austenite in at least said austenitic region;
- and
- a second heating step wherein
- heat is applied to the austenitic region of at least one of the two steel rails to raise and maintain the temperature of at least said austenitic region above the Ms temperature and below an A1 temperature for sufficient time, such that at least said austenitic region achieves a microstructure containing at least some tempered martensite and a (tempered martensite+bainite+pearlite+ferrite) content of at least 95%, and wherein
- tempered martensite is martensite with a hardness less than or equal to 600 Hv.
11 more elements
Dependencies are inferred from the claim text.