Method for joining of at least two unweldable materials, non-weldable directly to each other with thermal joining processes in a lap joint configuration, where a two step sequence is used consisting of a first step to apply a thermomechanical or mechanical surface protection layer on the surface of an unweldable material and a second step, where a thermal joining process is used to joint the sprayed layer with an applied layer sheet.

Method for joining of at least two unweldable materials, non-weldable directly to each other with thermal joining processes in a lap joint configuration, where a two step sequence is used consisting of a first step to apply a thermomechanical or mechanical surface protection layer on the surface of an unweldable material and a second step, where a thermal joining process is used to joint the sprayed layer with an applied layer sheet.

A steel sheet with a tensile strength (TS) of 1180 MPa or more, a member, and a method for producing them. In a region of the steel sheet within 4.9 μm in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 μm or more. The lowest Si concentration L.sub.Si and the lowest Mn concentration L.sub.Mn in the region within 4.9 μm in the thickness direction from the surface of the steel sheet and a Si concentration T.sub.Si and a Mn concentration T.sub.Mn at a quarter thickness position of the steel sheet satisfy the following formula (1):

L.sub.Si+L.sub.Mn≤(T.sub.Si+T.sub.Mn)/4  (1).

In a resistance spot welding method, test welding and actual welding in which a current pattern is divided into two or more steps are performed. In the test welding, a constant current of a different value is passed in each step, and a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume are stored as a target value. In the subsequent actual welding, when a time variation amount of an instantaneous amount of heat generated per unit volume deviates during any step from the results of the test welding, a current passage amount is controlled to compensate for the difference during a remaining welding time in the step. In the test welding, 0.3×I.sub.x≦I.sub.a<I.sub.x, where I.sub.a is the current in the first step, and I.sub.x is the current in second and subsequent steps.

An exterior panel is formed of superplastic materials, including an exterior skin of titanium to accommodate high thermal stresses imposed on hypersonic transport vehicles during hypersonic flight. The exterior skin is fixed to an underlying reinforcing skeletal structure consisting of a superplastic formable reinforcement (SFR) layer, for example a titanium, zirconium, and molybdenum (TZM) alloy, which supports the exterior skin whenever the latter may be heated to temperatures exceeding 1200 degrees Fahrenheit. The exterior panel includes a separate interior skin configured for attachment to a frame member such as a rib, stringer, or spar of the hypersonic transport vehicle. A multicellular core is sandwiched between the exterior and interior skins to impart tensile and compressive strength to the exterior panel. In one disclosed method, the core is superplastic formed and diffusion bonded to the exterior and interior skins.

The base member 3 can be attached to and detached from a base-holding member 5 without using tools and the like. The base-holding member 5 has a positioning mechanism that decides the position of the base member 3 on the base-holding member 5. Here, a reference part that decides the position of the base member 3 on the base-holding member 5 in a direction parallel to an optical fiber installation surface 2, which is an upper surface of the base member 3, is called a horizontal positioning reference part. Also, a reference part that decides the position of the base member 3 on the base-holding member in a direction vertical to the optical fiber installation surface 2 (the direction vertical to the horizontal positioning reference part), which is the upper surface of the base member 3, is called a vertical positioning reference part 6. That is, the horizontal positioning reference part and the vertical positioning reference part 6 are provided on the base-holding member 5.

The base member 3 can be attached to and detached from a base-holding member 5 without using tools and the like. The base-holding member 5 has a positioning mechanism that decides the position of the base member 3 on the base-holding member 5. Here, a reference part that decides the position of the base member 3 on the base-holding member 5 in a direction parallel to an optical fiber installation surface 2, which is an upper surface of the base member 3, is called a horizontal positioning reference part. Also, a reference part that decides the position of the base member 3 on the base-holding member in a direction vertical to the optical fiber installation surface 2 (the direction vertical to the horizontal positioning reference part), which is the upper surface of the base member 3, is called a vertical positioning reference part 6. That is, the horizontal positioning reference part and the vertical positioning reference part 6 are provided on the base-holding member 5.

Resistance spot welding of a thin-gauge steel workpiece to another steel workpiece is achieved through the combined use of specific spot welding electrodes and a pulsating welding current. Each of the spot welding electrodes has a weld face that is smaller in diameter than a typical steel spot welding electrode. And the pulsating welding current that is used in conjunction with the smaller-sized spot welding electrodes includes at least two stages of electrical current pulses.

Welding techniques, including, for example, resistance spot welding, can be used to join or weld two or more metal sheets together. A clamping force and an electric current can be applied to two or more sheets to create localized melting that combines the material of the two sheets. Applying a clamping force and a cooling current can include gradually decreasing the amount of the electric current applied to the weld while applying the forging force. By adjusting the amount of the electric current applied to the weld can allow the weld to cool gradually, which may reduce thermal stresses and allow the forging force to close cracks, pores, or otherwise be used to remove or prevent defects formed in the weld.

Welding techniques, including, for example, resistance spot welding, can be used to join or weld two or more metal sheets together. A clamping force and an electric current can be applied to two or more sheets to create localized melting that combines the material of the two sheets. Applying a clamping force and a cooling current can include gradually decreasing the amount of the electric current applied to the weld while applying the forging force. By adjusting the amount of the electric current applied to the weld can allow the weld to cool gradually, which may reduce thermal stresses and allow the forging force to close cracks, pores, or otherwise be used to remove or prevent defects formed in the weld.