Atsushi Danno

Hot forming of stepped steel shafts by wedge rolling with three rolls

Abstract A three-roll method has been developed as a means of avoiding the tendency for central cavity formation which occurs during the conventional wedge rolling of stepped shafts using two rolls, and the metal flow, as well as the optimum rolling conditions with this method, have been experimentally investigated by the use of steel and Plasticine billets. In the central portion of the products rolled by this method, a very small value of shear strain was observed but it was also noted that there is the generation of aradial compressive stress field, with little possibility of central cavity formation. The optimum forming and wedge angles of the wedge-shaped dies on the rolls were found to be 15–20° and below 15°, respectively, and a maximum reduction in area of up to 60–70% was possible in a single pass without the formation of any external defects on the rolled products.

A Cold Forging Oil Containing Phosphorus Type EP Additives

The galling prevention property of oils containing oleyl acid phosphate (OLAP) and/or phosphoric acid has been investigated. A synergistic effect was observed with the oil containing these two additives. Heat-treatment was found to effectively enhance the galling prevention property of the oil. Surface analyses showed more phosphate formed on workpiece surfaces after the tests, using the oils with superior galling prevention property. Oil analyses suggested that OLAP, phosphoric acid and water associated to form molecular aggregates, and that the association between OLAP and phosphoric acid was promoted by heat-treatment. An oil with the highest, chemical reactivity and galling prevention property was obtained by the addition of the two additives to the base oil, followed fry heat-treatment at 120°C for one hour with stirring. The pretreatment of the workpieces in this oil further increased the galling prevention property due to the effect of phosphate films preformed on the. workpiece surfaces. Presented...

New Lubricating Method for Warm Forging of Steel with Boron Oxide (B2O2)

Summary Boron oxide (B2O3) is a glass with low viscosity in the temperature range of warm forging. Lubrication properties of (B2O3) in warm forging of steels were mainly examined using the backward can extrusion test. On the inside surface of a can. a (B2O3) film formed on the surface of a billet contributed to reduce seizure. friction and heat damage of a punch. For the application of (B2O3) to warm forging. However, it was required to reduce friction at low temperatures and optimize the amount of (B2O3) as well as heating conditions. A practical method not only for satisfying thebe requirements but also for obtaining high lubrication properties of (B2O3) has been developed. This method was successfully applied to the production of cans with rectangular cross sections made of high strength steel.

Evaluation of galling prevention properties of cold-forging oils by ball penetration test

Abstract A ball penetration test has been devised as a new laboratory-scale cold-forging test for determining the galling prevention properties of lubricants. The galling prevention properties of cold-forging oils were clearly classified by this test. After the tests, various reaction products were detected on the workpiece surfaces. The oils with higher reactivity exhibited superior galling prevention properties. The order of performance as determined by the ball penetration test correlated well with that determined by the backward can extrusion test, which is generally recognized as a standard cold-forging test. Moreover, the ball penetration test requires no tedious test procedures, in contrast with conventional cold-forging tests. Judging from the results obtained, the ball penetration test is effective as a means of evaluating the galling prevention capacity of cold-forging oils adequately and easily.