Abstract: A TIG welded joint in a high-Mn content steel material that can be formed with reduced occurrence of hot cracking during the welding process and has high strength and excellent cryogenic impact toughness. In the TIG welded joint, the high-Mn content steel material has a chemical composition including, by mass %, C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 18.0 to 30.0%, P: 0.030% or less, S: 0.0070% or less, Al: 0.010 to 0.070%, Cr: 2.5 to 7.0%, N: 0.0050 to 0.0500%, and O: 0.0050% or less, the balance being Fe and incidental impurities, and a weld metal has a chemical composition including C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 15.0 to 30.0%, P: 0.030% or less, S: 0.030% or less, Al: 0.100% or less, Cr: 6.0 to 14.0%, and N: 0.100% or less, the balance being Fe and incidental impurities.

Abstract: A TIG welding filler metal is provided that has a composition including, by mass %, C: 0.20 to 0.80%, Si: 0.15 to 0.90%, Mn: 15.0 to 30.0%, P: 0.030% or less, S: 0.030% or less, Cr: 6.0 to 15.0%, and N: 0.120% or less, the balance being Fe and incidental impurities. Where necessary, the filler metal may contain one or two selected from Ni and Mo, may further contain one, or two or more selected from V, Ti, and Nb, and may additionally contain one, or two or more selected from Cu, Al, Ca, and REM. This configuration reduces the occurrence of welding cracks during TIG welding, that is, realizes excellent hot crack resistance, and allows for easy production of a weld joint having high strength and excellent cryogenic impact toughness.

Abstract: A system for control of the discharge pressure of an input clutch hydraulic servo at the time of a D→N shift, in which the peak value (DN_Omega_max) rate of change of the rotational speed of an input shaft increases if the initial value (DN sol Sweep Start SLT signal) of the pressure adjusting control becomes high or low. A convergence region (DN_Omega_limit_max) is provided. On the basis of comparison between the previous peak value (DN_Omega_max_ave1) and the present peak value (DN_Omega_max_ave2), and the direction of correction, the learning is performed in accordance with various maps in a direction toward the convergence region.

Abstract: A system for control of the discharge pressure of an input clutch hydraulic servo at the time of a D→N shift, in which the peak value (DN_Omega_max) rate of change of the rotational speed of an input shaft increases if the initial value (DN sol Sweep Start SLT signal) of the pressure adjusting control becomes high or low. A convergence region (DN_Omega_limit_max) is provided. On the basis of comparison between the previous peak value (DN_Omega_max_ave1) and the present peak value (DN_Omega_max_ave2), and the direction of correction, the learning is performed in accordance with various maps in a direction toward the convergence region.