Studies On Preparation And Cooling Characteristics Of A New Water-based Quenching Medium

Quenching is a metal heat treatment process that the steel is heated to above the critical point temperature and heat preservation time make its austenitizing, then to cooling is greater than the critical cooling rate, and thus get the martensite structure of the steady state. The main purpose of quenching is to improve the hardness and wear resistance of steel, then get the machining parts of excellent mechanical properties. Quenching is one of the most important working procedure in heat treatment process, and the cooling is the key factor of success. Therefore, select the excellent performance of quenching cooling medium is an important problem of quenching process.At present, the Poly alkylene glycol quenching medium (PAG) as the representative of organic polymer quenching medium as a new type of quenching medium. It has gradually replaced the trend of quenching oil with its outstanding features, and has become one of the main development direction of heat treatment in the future, the Poly alkylene glycol quenching medium is made up of Poly alkylene glycol, Cooling rate adjustment additive, rust protection, preservative, defoaming agent and water.The article mainly to select the Poly alkylene glycol that it is the most conforms to the requirement of cooling characteristics, through Labview temperature acquisition system is used for measuring the cooling characteristics of Poly alkylene glycol of three different average molecular weight, and the optimum ratio of cooling rate adjustment additive of Polyvinyl pyrrolidone of two different average molecular weight. Several qualified rust protections of rust resistance are found out by referencing the rust prevention test of standard <Synthetic cutting fluids>, then the effect of cooling characteristics of adding different rust protections on the quenching medium are determined by the Labview temperature acquisition system. It is designed to select the rust prevention with the best performance. Then a certain amount of preservative and defoaming agent are added into the quenching medium. The formulation of the new water-based quenching medium is:3%～12% Poly alkylene glycol C,0.45% composite cooling rate adjustment additive (0.375% Polyvinyl pyrrolidone A+0.075% Polyvinyl pyrrolidone B),0.1% Composite rust protection (0.05% Sodium tetraborate decahydrate +0.05% Trisodium phosphate),0.35%o preservative (Salicylic acid),0.1‰ defoaming agent (Polyethylene glyclol) and water.In order to research the cooling characteristics of the new quenching medium, the article studies the effect of cooling performance of the home-made quenching medium with the change of concentration, temperature and stir of medium. Experimental results show that:the cooling speed of home-made quenching medium gradually reduce along with the increase of concentration of Poly alkylene glycol, and the cooling speed of high temperature area decrease obviously, the low temperature area to reduce the relative is not obviou. The cooling speed of home-made quenching medium gradually reduce along with the increase of temperature of Poly alkylene glycol, and the maximum cooling speed decrease obviously, the cooling speed of low temperature area is neaely unchanged. Stirring improves the cooling speed of high temperature area of quenching medium, and does not much impact on the cooling speed of low temperature area.Compared with water, quenching oil and foreign product Dow UCONE. Experimental results show that:the cooling capacity of home-made quenching medium between water and quenching oil, and the cooling capacity is quite UCONE quenching medium.Low carbon steel 20CrMnTi, medium carbon steel 42CrMo and high carbon steel GCrl5 are used on quenching test with home-made quenching medium, water and quenching oil, then measured hardness distribution curve of three kinds of steel after quenching. Results show that:the hardness of 20CrMnTi reaches 51.1 HRC after quenching with 3% home-made quenching medium, and the hardness reaches 51.3 HRC after quenching with water. The hardness of 42CrMo reaches 62.2 HRC after quenching with 12% home-made quenching medium, and the hardness reaches 60.2 HRC after quenching with quenching oil. The hardness of GCrl5 reaches 67.7 HRC after quenching with 8% home-made quenching medium, and the hardness reaches 58.1 HRC after quenching with quenching oil. Home-made quenching medium can apply different carbon content steel, its application range.