Effect of prior heat treatment on nitride-layer formation and the properties of steel 30KhGSA

1991 ◽  
Vol 33 (2) ◽  
pp. 130-134
Author(s):  
V. N. Ketkin ◽  
V. G. Sorokin ◽  
T. A. Petrova ◽  
V. G. Rakin
Keyword(s):  
Heat Treatment ◽  
Nitride Layer ◽  
Layer Formation ◽  
Steel 30Khgsa ◽  
Prior Heat Treatment

Mechanical Behavior of Surface Nitrided and Heat-Treated Laser Welded Ti-6Al-4V

2016 ◽  
Vol 1135 ◽  
pp. 167-178
Author(s):  
Helio Rubens Simoni ◽  
Antonio Jorge Abdalla ◽  
Carlos Antonio Reis Pereira Baptista ◽  
Milton Sergio Fernandes de Lima
Keyword(s):  
Heat Treatment ◽  
Fusion Zone ◽  
Fatigue Behavior ◽  
Base Material ◽  
Nitride Layer ◽  
Zone Structure ◽  
Additional Advantage ◽  
Heat Treated ◽  
Controlled Structure ◽  
Intrinsic Reactivity

The welding of the titanium alloy Ti-6Al-4V has been reported to be difficult because of the intrinsic reactivity with oxygen and also because the weld usually produces an unbalanced α/β structure. This contribution deals with a heat treatment of the laser welded Ti-6Al-4V alloy in a CVD nitriding chamber. The heat treatment aims to obtain a fusion zone structure similar to the base material. An additional advantage of the method is creating a hard nitride layer at the surfaces of the piece, increasing the hardness. The CVD treatment at 850°C per 2 hours proved to be efficient to transform the as-welded martensitic structure to a biphase α/β diffusion controlled structure. Although the fusion zone was soft after the treatment (330 HV), the surface is hard attaining about 750 HV. The tensile strength and ductility after welding were very similar to the base material. However, the yield strength decreased from 1030 MPa to 880 MPa and the uniform strain was reduced from 8 to 1% after the CVD treatment. The fatigue behavior was quite different depending on the testing conditions. For the rotating bending condition, the higher fatigue limits, around 400 MPa, were observed for the CVD-treated weld coupon. However, the fatigue behavior in uniaxial conditions was very similar to the as-welded condition and the CVD-treated weld, attaining the fatigue limits at 250 MPa.

NON-DESTRUCTIVE MAGNETIC TESTING OF THE PHYSICAL AND MECHANICAL PROPERTIES OF MISSION-CRITICAL MOUNTING COMPONENTS MADE OF 30HGSA STEEL

2020 ◽  
pp. 4-13
Author(s):  
S. G. Sandomirski
Keyword(s):  
Heat Treatment ◽  
Remanent Magnetization ◽  
Physical And Mechanical Properties ◽  
Medium Carbon Steel ◽  
Tempering Temperature ◽  
Plastic Properties ◽  
Demagnetizing Field ◽  
Steel 30Khgsa ◽  
Mission Critical ◽  
Increased Strength

The mounting products with mission-critical functions (bolts, studs, rods) used in aviation technology are subject to increased strength, hardness, and wear resistance requirements. They are made of specially developed medium-carbon steel 30KhGSA alloyed with chromium, manganese, and silicon. According to international classifications, the steel 30KhGSA is steel 42CrMo4-T (EN), 1.7225 (DIN, W.NR), 4140H (AISI). The balance between the strength and plastic properties of the products is achieved by the choice of the mode of their heat treatment – quenching and subsequent medium or high temperature tempering. Possible deviations in the chemical composition of the product materials and the modes of their heat treatment from the prescribed ones lead to unacceptable deviations of the properties of the products. This requires monitoring all products. The physical basis of magnetic structural analysis relies on the fact that mechanical and magnetic properties of steels are sensitive to the structural transformations occurring in them during thermal treatments. It has been proven that the coercive force Нc and the remanent magnetization Мr of many steels are related to their structure. When controlling mass batches of products, the best results in reliability and productivity are achieved by magnetization of products when they fall through a coil with the direct current and measuring the remanent magnetic flux Fd in the product. In this case, Fd in the product is not proportional to Mr, but to Hc of the product material. A characteristic feature of alloyed steels with a carbon content greater than 0.3 %, including steel 30KhGSA (steels 42CrMo4-T, 1.7225, 4140H, 37Cr4, 41Cr4, 46Cr2 and others), is a non-monotonic change in Hc with an increase in the tempering temperature Tо of products. Therefore, magnetic quality control of products from such steels requires a specific procedure. To test the tempering mode of such products, we have proposed to expose the magnetized products to a graded demagnetizing field with the strength Нp, before measuring Fd. The developed method allows us to choose the value of Hp, at which the optimum sensitivity to changes in Tо is achieved while monitoring products of specific sizes. In this report we show that such testing is based on the sensitivity of Fd in the product after its reverse magnetization in the field Hp to the remanent magnetization of the material Mr. We also article the technical means ensuring application of the developed methodology in industrial settings with a control output of up to 2 products per second. Examples of application of the method for controlling the hardness of small bolts made of steel 30HGSA, intended for use in aircraft construction, are given.

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