The invention relates to an apparatus for making a seamless hollow body (10) from a solid round block (7) of steel with a diameter <95% of the diameter of the solid round block by means of a two-roll cross-rolling mill with a piercing mandrel (3) held between the inclined roll (1) and including a piercer (5) and at least one smoothing part (4) using pass-closing guides, or by means of a three-roll cross rolling mill with a piercing mandrel held between the inclined rolls and including a piercer and at least one smoothing part, wherein the distance of the rolls is adjusted in a particular manner at the narrowest cross-section (2) in relation to the diameter of the used round block, and the position of the piercing mandrel is adjusted in relation to the narrowest cross-section of the rollers.

In a method of making a seamless hot-finished steel pipe a billet heated to a shaping temperature is pierced by a first shaping to a thick-walled hollow ingot which subsequently undergoes a radial forging process using an internal tool inserted in the hollow ingot and at least two forging jaws of a forging machine. The forging jaws act on the outer surface area of the hollow ingot, wherein the hollow ingot is turned and axially advanced in a clocked manner in the idle stroke phase of the forging jaws.

A method for nondestructive testing of the pipes for detecting surface flaws using magnetic leakage flux is disclosed. With of the method, flaws can be detected and analyzed in near-real-time while the pipe is produced. The data obtained with inductive coils, Hall sensors or GMR sensors are digitized, the digital data are buffered in a first memory, and a subset of the digital data are copied into a second memory. The copied data are transformed with a wavelet transformation and the resulting wavelet coefficients are filtered and/or modified. In an alternative embodiment, the digital data can be continuously supplied to a routine for wavelet transformation, which is performed using cascaded digital signal processing routines. The evaluated variable is compared with a reference value, wherein a determined flaw-based signal can be unambiguously associated with the position of the flaw.

An alloy steel, includes 0.12 to 0.25 wt. % C, 0.40 wt. % or less Si, 1.20 to 1.80 wt. % Mn, 0.025 wt. % or less P, 0.010 wt. % or less S, 0.01 to 0.06 wt. % Al, 0.20 to 0.50 wt. % Cr, 0.20 to 0.50 wt. % Mo, 0.03 to 0.10 wt. % V, 0.20 wt. % or less Cu, 0.02 wt. % or less N, 0.30 to 1.00 wt. % W, and the balance iron and incidental impurities, for making high-strength, weldable seamless steel tubes for structural application, through a hot rolling process and subsequent quenching and tempering.