CN102912225A

CN102912225A - Method for improving hardenability of 40MnBH steel for hardenability maintenance structure

Info

Publication number: CN102912225A
Application number: CN2012104640686A
Authority: CN
Inventors: 姜德刚; 何建中; 高明星
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd; Inner Mongolia Baotou Steel Union Co Ltd
Priority date: 2012-11-16
Filing date: 2012-11-16
Publication date: 2013-02-06

Abstract

The invention relates to a method for improving hardenability of 40MnBH steel for a hardenability maintenance structure and is characterized in that ferrovanadium is added to achieve microalloying of vanadium on the basis of chemical components of 40MnBH steel prescribed by GB/T5216-2004 standards during smelting, so that final 40MnBH steel comprises, by weight, 0.38% to 0.42% of carbon, 0.17% to 0.35% of silicon, 1.10% to 1.35% of manganese, less than or equal to 0.025% of phosphorus, less than or equal to0.025% of sulfur, 0.0010% to 0.0025% of boron, 0.038% to 0.048% of vanadium, and the balance ferrum and inevitable impurities. The method has the advantages that the kind of added microalloy elements is small; the adding method during smelting is simple, and the microalloy elements can be added with other alloy elements; addition amounts of microalloy elements are small, the cost is low, and the vanadium accounts for 0.038% to 0.048%; special technical processes are not needed during smelting and rolling, the comprehensive effectiveness is enhanced, and the effect of improving the hardenability is obvious; and the heat treatment method is simple when users use the 40MnBH hot-rolled steel, the heating temperature is not needed to be increased deliberately, the comprehensive performance of produced motor shaft products is good, machining properties are good, and the machining amount is small.

Description

A kind of method that the hardening capacity structure is used the 40MnBH steel hardenability of protecting that improves

Technical field

The present invention relates to a kind of the raising and protect the hardening capacity structure with the method for 40MnBH steel hardenability, belong to the metal material field that metallurgical industry is produced.

Background technology

Baogang adopts the chemical composition of GB/T5216-2004 standard code, guarantor's hardening capacity structure of producing for the auto parts machinery user in the first batch uses the 40MnBH steel hardenability defective, by analysis research (is smelted by Composition Design and intermediate frequency furnace, forging test) learns, it is owing to lacking the element of necessary raising hardening capacity in this steel that the 40MnBH steel hardenability of producing does not conform to, according to GB be draft on the basis of electric furnace smelting process and stipulate (eaf process smelt to use more steel scrap, all much more than using the molten iron converter process to smelt from residual element kind or component proportions), therefore, just be inevitable according to GB employing molten iron converter process smelting 40MnBH steel hardenability is defective.Guarantor's hardening capacity structure that the GB/T5216-2004 standard code also is described thus is to sum up out on the basis that eaf process is smelted with the chemical composition of 40MnBH steel, and do not consider and stipulate chemical composition that different smelting technologyes are required and on the impact of performance, if adopt the molten iron converter process to smelt, its hardening capacity is difficult to satisfy the Vehicles Collected from Market demand.

Summary of the invention

The objective of the invention is to adopt the molten iron converter process to smelt the underproof defective of 40MnBH steel hardenability for the chemical composition that overcomes according to the GB/T5216-2004 standard code, a kind of method that the hardening capacity structure is used the 40MnBH steel hardenability of protecting that improves is provided.

Technical scheme of the present invention is as follows:

Method of the present invention is: during smelting, realize the microalloying of vanadium by adding vanadium iron on the basis of the chemical composition of the 40MnBH of GB/T5216-2004 standard code steel, so that the weight percentage composition of final 40MnBH steel consists of: carbon 0.38%～0.42%, silicon 0.17%～0.35%, manganese 1.10%～1.35%, phosphorus is less than or equal to 0.025%, sulphur is less than or equal to 0.025%, boron 0.0010%～0.0025%, vanadium 0.038%～0.048%, all the other are iron and inevitable impurity.

Described guarantor's hardening capacity structure 40MnBH steel, steel production enterprise is delivered goods with As rolled, the user is after machining and suitable thermal treatment (quenching and tempering technique), the mechanical property of its material is: yield strength 〉=980MPa, tensile strength 〉=785MPa, unit elongation 〉=10%, reduction of area 〉=45%, ballistic work A _KU2〉=47J, Brinell hardness HBW≤207.

Steel of the present invention namely adopt the method for vanadium micro-alloying by adding vanadium iron, the scope of control residual element meets GB and customer requirements (Cu≤0.20%; Ni≤0.25%, Cr≤0.25%), through reasonable component design and optimization, cooperate rational heating cycle and rolling technology, but the hardening capacity of Effective Raise 40MnBH steel.The automobile shafts series products hardening capacity 100% that the user adopts these 40MnBH As rolled steel to produce is qualified.

Advantage of the present invention: method adding microalloy element kind of the present invention is few, only adds vanadium a kind of; Adding method is simple during smelting, together adds with other alloying elements to get final product; The microalloy element add-on is few, and cost is low, and the vanadium weight percentage only is 0.038%～0.048%; Smelt and the rolling special processes process that do not need, comprehensive effectiveness is high, improves the successful of hardening capacity; Heat treating method was simple when the user adopted these 40MnBH As rolled steel, and Heating temperature does not need deliberately to improve, the automobile shafts series products good combination property of production, and machinability is good, and amount of machining is little.

Embodiment

The process scientific and technical personnel specially grinding and testing at the 25kg vacuum induction furnace, and the industrial molten steel composition scope of design, summary and optimization is as shown in table 1, and the steel grade name is called 40MnBH.

Table 1 is protected the composition requirement of hardening capacity structure iron 40MnBH, w%

Technical process is: (casting blank specification is 240mm * 240mm) to 80t converter smelting → LF stove refining → VD stove vacuum outgas → continuous casting.

THE INDUSTRIAL TRIAL 3 stove steel, concrete process parameter control is as follows:

1) converter production

The carbon content of converter terminal molten steel, phosphorus content and tapping temperature are as shown in table 2.

Temperature and the composition of table 2 40MnBH tapping

Test number	Tapping temperature, ℃	The tapping carbon content, w%	The tapping phosphorus content, w%
				1 ^#	1636	0.04	0.019
2 ^#	1639	0.07	0.017
				3 ^#	1638	0.05	0.015

2) the LF stove is produced

Table 3 40MnBH refining station off normal composition and temperature

Test number	C，w%	Si，w%	Mn，w%	P，w%	S，w%	B,w%	V，w%	Temperature, ℃
									1 ^#	0.40	0.36	1.35	0.022	0.008	0.0019	0.041	1567
2 ^#	0.40	0.31	1.37	0.019	0.006	0.0025	0.046	1559
									3 ^#	0.40	0.23	1.36	0.018	0.005	0.0010	0.043	1561

3) continuous casting production

Table 4 40MnBH steel continuous casting superheating temperature and pulling rate control

Test number	Superheating temperature, ℃	Pulling rate, m/min
			1 ^#	30	0.65
2 ^#	27	0.65
			3 ^#	26	0.65

So far finish bloom production of the present invention, below be the described continuous casting steel billet of employing, the technique of producing round steel, technical process is: steel billet → process furnace heating → rolling.

4) steel rolling production

The steel billet start rolling temperature of 3 stove steel was rolled into φ 110mm round steel to steel billet about 1150 ℃ greater than 2 hours heat-up time in process furnace.

5) terminal hardening capacity check

Take a sample at φ 110mm round steel, carry out the end quenching check.After 3 stove 40MnBH φ 110mm round steel were pressed the end quenching art breading of GB5216-2004 regulation, assay saw Table 4.The result shows complete conformance with standard requirement.

Table 53 stove 40MnBH steel end quenching test results

6) user produces service check after the product thermal treatment

The user adopts 40MnBH φ 110mm round steel to be swaged into cardan shaft through heated mould, quenches and tempering heat treatment after a small amount of machining, checks all other performances, all meets the GB5216-2004 standard-required.

This shows, the properties of 3 stove 40MnBH steel hardenabilities of the present invention and GB5216-2004 standard code meets the demands fully, so the V content range of steel grades design and raising hardening capacity is rational.

Claims

1. one kind is improved the method that the hardening capacity structure is used the 40MnBH steel hardenability of protecting, it is characterized in that: during smelting, realize the microalloying of vanadium by adding vanadium iron on the basis of the chemical composition of the 40MnBH of GB/T5216-2004 standard code steel, so that the weight percentage composition of final 40MnBH steel consists of: carbon 0.38%～0.42%, silicon 0.17%～0.35%, manganese 1.10%～1.35%, phosphorus is less than or equal to 0.025%, sulphur is less than or equal to 0.025%, boron 0.0010%～0.0025%, vanadium 0.038%～0.048%, all the other are iron and inevitable impurity.