Process for producing forged product

Patent metadata

Field	Value
Publication number	US-9738945-B2
Application number	US-201214374409-A
Country	US
Kind code	B2
Filing date	Jan 31, 2012
Priority date	Jan 31, 2012
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A forging process is conducted in a temperature range of 350-600° C. on at least a portion that is required to have a fatigue strength in an intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging on a steel in which N is not greater than an amount at which N is unavoidably dissolved as a solid, thereby improving strength of the portion that is required to have a fatigue strength. With this, there is provided a forged product having a good strength and a low price.

First claim

The invention claimed is:

1. A process for producing a forged product comprising:
conducting a forging process in a temperature range of 350-600° C. on at least a portion required to have a fatigue strength of an intermediate forged product, the intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging on a steel in which nitrogen is less than 0.0030 mass %, thereby improving strength of the portion that is required to have a fatigue strength,
wherein the steel contains, by mass %, chemical components of 0.20-0.60% C, 0.05-1.50% Si, 0.30-2.0% Mn, 0.03% or lower and greater than 0% P, 0.10% or lower and greater than 0% S, 1.0% or lower and greater than 0% Cu, 3.5% or lower and greater than 0% Ni, and 1.5% or lower and greater than 0% Cr, Fe as a remainder, and unavoidable impurities.

2. The process for producing a forged product as claimed in claim 1 , wherein the steel further contains 0.001-0.06 mass % Al.

3. The process for producing a forged product as claimed in claim 2 , wherein the steel contains as another element 0.30 mass % or lower and greater than 0 mass % Bi.

4. The process for producing a forged product as claimed in claim 1 , wherein the steel contains 0.02-3.5 mass % of Ni.

5. The process for producing a forged product as claimed in claim 1 , wherein a temperature of the portion required to have the fatigue strength is made to reach the temperature range by using excess heat of the hot forging when conducting the forging process.

6. The process for producing a forged product as claimed in claim 1 , wherein, after the hot forging, a temperature of the intermediate forged product is lowered to room temperature, and then a temperature of the portion required to have the fatigue strength in the intermediate forged product is increased to the temperature range to conduct the forging process.

7. The process for producing a forged product as claimed in claim 1 , wherein the portion required to have the fatigue strength in the intermediate forged product is a flange portion of a crankshaft.

8. The process for producing a forged product as claimed in claim 1 , wherein the portion required to have the fatigue strength in the intermediate forged product is a gear shaft portion of a crankshaft.

9. The process for producing a forged product as claimed in claim 1 , wherein the portion required to have the fatigue strength in the intermediate forged product is a pin portion of a crankshaft.

10. The process for producing a forged product as claimed in claim 1 , wherein the portion required to have the fatigue strength in the intermediate forged product is a journal portion of a crankshaft.

Assignees

• Yoshida Jun
• Kaneko Daisuke
• Iwata Noriyuki
• Nissan Motor

Inventors

• Yoshida Jun
• Kaneko Daisuke
• Iwata Noriyuki

Classifications

• C21D2211/005

  Ferrite · CPC title

• C21D9/30

  for crankshafts; for camshafts · CPC title

• C22C38/38

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

• B21K1/08

  crankshafts · CPC title

• C22C38/60

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